# Question
Title: What are those 6 extra studs for in 42000 Grand Prix racer?
I recently purchased a set, Technic 42000 Grand Prix Racer, that I am very happy with. However, I am perplexed by the fact that the set came with 6 extra transparent 1x1 round plates (studs).

As you can see, this was clearly not a mistake, as they are shown in the instruction manual. So my question is, does anyone know what these are for? My guess was that perhaps the Designer is signing his/her name to the set in a quirky way. Can anyone explain?

# Answer
Sariel's assembly video shows that he ends up not using those 6 studs for the car assembly

but wait! if you scroll down into the comments:

he explains that the pieces are used for the B-model:
> 8 votes

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Tags: design
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title: What is the "Module" of a LEGO gear?

text:
# Question
Title: What is the "Module" of a LEGO gear?
> Module, m this indicates the tooth size and is the number of mm of pitch circle diameter (p.c.d.) per tooth. For gears to mesh, their modules must be equal. Gear ISO standards and design methods are now normally based on the module. EG a gear of module 3 has 16 teeth, its pitch circle diameter is: 3 x 16 = 48 mm.

Source: Plymouth University. Gear Tooth Nomenclature.

I am curious as to which non-LEGO gears will mesh well with LEGO gears, but this is one of the more important numbers as far as figuring that out, yet I don't see the concrete number mentioned in any of the various LEGO gear descriptions/tutorials that show up when I search for it

To be very clear, all I am looking for is either single number, or an answer of "LEGO doesn't follow the mentioned Gear ISO standards".

# Answer
> 13 votes
**Quick answer:** LEGO gear module is 1 (metric).

See Section 3.4 at this link: http://bdml.stanford.edu/Main/CrawlerNotes

The consensus seems to be the following:

* Lego gears have a metric module of 1, which is the same as a pitch of 25.4 teeth per inch of diameter.
* Pressure angle is likely to be about 20 degrees. (This is the most common angle with modern gearing.)
* Face width is approximately 1/8 inch. Perhaps more precisely: b = 0.14 inches? - according to a measurement somebody took with calipers in 2011. But note that not all LEGO gears have the full face width. In particular, the crown gears (LEGO's version of bevel gears) do not have a full face width.

From http://orionrobots.co.uk/Lego+Specifications:

> In the Lego system, technic gears have a ratio that the number of teeth are 8 times the diameter, or 16 times the radius in stud pitch. Conveniently - the number of studs, and Diameter in Millimeters seem to be the same. Note: one "stud" is 8mm. So: 16 tooth gear is 2 studs = 16mm =\> diametral pitch = 1mm.

Also, I have personally 3D printed custom gears with a pressure angle of 20 degrees and a module of 1, and these meshed perfectly with my other LEGO gears.

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Tags: technic, terminology, gears
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title: Which set includes a large white mask

text:
# Question
Title: Which set includes a large white mask
I bought a sealed bag at Goodwill but It did not include any information on what set it is from.

Pieces look like large white body plates, skeletal/Stormtrooper mask and tusks.

# Answer
The mask in the first picture is from the Hero Factory set Witch Doctor. The other pic looks like it's from the same set.
> 2 votes

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Tags: piece-information, hero-factory
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# Question
Title: EV3 parallel MyBlocks, but only one working
TL;DR = Is there any obvious reason why a MyBlock, added twice in parallel to a program, will only run one of them?

---

In my EV3-G program, I have a MyBlock which uses the Proximity Heading to control a motor so that the heading is always straight ahead. (It has some added complexity, as it slows down when getting close, etc.)

My robot-arm has two infrared sensors, one mounted horizontally, one mounted vertically, so the arm can always point at the beacon... and the MyBlock has been setup with parameters, so that the corresponding port/motor numbers are passed in.

Is there any reason why two MyBlocks, running in parallel, would only work on one of those blocks, and not the other? (When debugging, both blocks are "shimmering", show they are both apparently running.)

I have double-tripple-quadruple checked that all the flow-control, sensor and actions are working with the correct parameter values, and running each block individually works perfectly.

I have also replicated (at great length) the blocks in brand new programs, and they work without issue.

Why would two blocks running in parallel not work, when the same code replicated on the program does?

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**UPDATE**

As requested (and I should have done originally).

Here is the MyBlock. It starts with 3 parameters, the sensor port, the motor port and an "offset" - all numeric. The loop starts, and a direction heading reading is taken. It then uses the "offset" value, and passes "offet - 5" and "offet + 5" into the range

Based on the boolean value from the range, if the current heading value is within the range, then it runs the motor at a "graded" speed, based on the heading value. Therefore as it gets closer to 0 the slower the motor is run.

If the current heading value is outside the range, then the motor is run at a non-variable speed... in this case if the value is below the "offset" value.

And in this case if the value is above the "offset" value.

The program simply calls two instances of the MyBlock. If I run the left one, the horizontal detection and movement works without issue - if I run the right one, the vertical detection and movement works without issue.

But, if I run the following, **only the last MyBlock to be wired works**. There is literally movement from just one direction motor.

# Answer
> 7 votes
I could not find this in the help file, but according to this thread "Another little known characteristic of MyBlocks is that they aren't re-entrant. No two copies of the same MyBlock can be running at the same time."

I tried a few simple programs in EV3-G and confirmed that this is true. The order in which they run appears to be random.

# Answer
> 3 votes
MyBlocks are not reentrant; only one thread can be using the block at a time. When a second thread tries to execute a MyBlock that is being used by another, the second thread blocks until the first thread exits the block.

This normally isn't a problem for MyBlocks that do simple calculations. They finish quickly and all threads make progress. But if a MyBlock contains a loop or wait, other threads that use the same MyBlock can be blocked indefinitely.

From the debugging view, a blocked MyBlock shows as active. This makes it very difficult to debug. You might try placing different sounds before and after the MyBlock, to see which thread is getting stuck.

A simple solution is to create multiple copies of the offending MyBlock and have each thread run their own copy.

(DavidL's answer was fine. I just offer this for more completeness. Happy programming!)

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Tags: mindstorms, ev3, programming
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# Question
Title: What year did the minicon "micro BrickCon" first appear at "BrickCon"?
It seems like minicons (a minicon is a LEGO display consisting of minilander figures looking at miniland scale tables populated by microscale MOCs) are popping up everywhere lately.

The last known sighting was in Melbourne, so the theme has officially gone global. Before it became a theme at LEGO conventions across North America, and now the world.

What year did the first *micro BrickCon* go on display at BrickCon in Seattle?

# Answer
In the blog of Tom Aplhin he mentions regarding Microscale

> Steve Oakes, a long-time LEGO builder in Seattle area started a tradition 4 years ago to re-create the BrickCon Public Convention at a smaller scale. His display is called “Micro BrickCon”

*(Edit: The conversation between Tom and myself was in a loud room with lots of activity. He is correct about everything except the year.)*

After building and displaying an 8.5 foot stern paddle wheel ferry boat at BrickCon 2011, I decided it would be easier to build smaller MOCs. I kicked the idea around for a while, and then came up with the concept of making a micro-con. Mariann Ansunuma, former miniland builder at Legoland, and current maker of awesome microscale Lego jewelry, liked the idea and took me under her wing. I built 2 tables, displays and minilanders to display at BrickCon 2012. I was very pleased when Mariann brought along a third table, displays, and minilanders to add to mine.

After the initial Micro BrickCon MOC was displayed, Mariann, who travels to various cons with her vendor booth, took her portion of the MOC and introduced it to cons across America. It has since become a theme featured across N. America, Canada, Germany, and Australia.

In 2012, the MOC was just a MOC. However, micro BrickCon was so well received, in 2013 it became and remains it's own theme. In 2012 7 builders contributed one thing or another to make the MOC better. In 2013 and 2014, 22 builders contributed, and this year, 2015, 29 builders joined in. -Major Stackings
> 7 votes

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Tags: history, theme, micro-scale
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# Question
Title: How can I build a LEGO structure based on a real building?
I have a grandson who wants to build a LEGO building that looks like the high rise building I live in.

# Answer
1. Take pictures of your building, of as many sides as possible
2. Take measurements or find blueprints of the building. Length, width, height, height between floors, size of balconies etc.
3. Convert these dimensions to LEGO dimensions. For this, figure out the scale you want to build in first (e.g. 1:40, which is "minifig scale" - but check out this post for some caveats). You can use Sariel's calculator to find out what this means for how many bricks you need.
4. For best results, design the whole building in LEGO Digital Designer (LDD) or LDraw first. This will save you from making unnecessary brick purchases before you have finalized your model
5. Get a brick inventory from LDD/LDraw once you have your final model.
6. Use a service like Bricklink or BrickOwl or Lego's own Pick-a-Brick to buy the bricks you need in the quantities necessary, after accounting for all the bricks you already have. Alternatively, you can look at other available sets to see if some of them carry the bricks you need in large quantities - this might be cheaper (you could even sell the not-needed bricks back via BrickLink etc.).
> 10 votes

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Tags: modular-buildings
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# Question
Title: Can i change the way the ir remote works?
I bought an EV3 and the first thing that I want to do with it is control models with the remote.

I finally discovered how to do this after a long search.

It can control the Formula EV3 racing car with rack and pinion steering (where the angle of the 2 front wheels change instead of the 2 back wheels turning in the opposite direction to turn the car) When you use wheels it doesn't turn like when you use the other type of tires.

I'd like to use the remote that comes with the EV3 to do this, but I'm not sure how to modify the remote to support this type of control?

# Answer
If I understand your question correctly, you are asking how to use the following remote to control traditional car that has front wheel rack and pinion steering rather than a vehicle that skid steers using the rear wheels. Here's the remote:

This isn't ideal for controlling steering because both sets of buttons point forward. The easiest solution is to attach a wheel on the side of the remote that actuates one set of controls like this. Here's an example using the PF remote that could be adapted to work with the EV3 remote.

I don't know what your vehicle design looks like, but you may also want some sort of return to center steering system on the motor controlling the orientation of the front wheels if you haven't already built one. Here's one simple example of this:
> 1 votes

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Tags: ev3
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# Question
Title: What is the easiest way to sell Lego sets for a good price?
I have a HUGE collection of LEGO sets that I want to sell. Ebay is too cheap and Craigslist takes too long. Is there an easier and faster way to get some good money?

# Answer
Unfortunately, even with the best market conditions, there is always a trade off between selling things at a high price and selling things fast. That's just a principle of marketing.

That said, you might consider these options:

**BrickLink / Brick Owl**

These are sites that specialize in trading LEGO. I can't comment further, as I've only used these sites as a buyer, not as a seller. As a buyer, I've been impressed.

Both Bricklink and Brick Owl take a commission for each order that goes through.

**Local Ads**

Some people still rely on newspaper etc. adds for their purchases. Although they reach a smaller audience, they have three advantages over eBay:

1. Ads are generally a fixed price, so fees don't depend on selling price - ideal for large lots of LEGO.
2. If you sell locally, you don't have to charge postage, as buyers can generally collect.
3. It is arguable that people who mainly buy from local adds are generally less well informed about "realistic" prices than people who use web-based purchasing options, so may be willing to pay a little more (although this cuts both ways - they may under-estimate the true price of things, too).

**eBay**

Despite your aversion to eBay, it is still be your best bet, simply because you'll reach such a large market. Prices on eBay are driven by the market - by what people are willing to pay. For this reason, I'm not sure that it makes sense to say that it is "too cheap".

To get the best price for your LEGO, I suggest using the fixed price listing feature, setting the price at the lowest you're willing to accept. Of course, it may take a little longer to shift your collection if your prices are at the high end of what the market can tolerate. An excellent picture and a good description make a big difference, too, as can your willingness to ship overseas. If you do decide to ship internationally, don't make the mistake of underestimating postage costs.

I use eBay for all my LEGO sales, and I'm generally happy with the results. The only down-side is that the fees can be quite high, but I generally accept that for the convenience.
> 12 votes

# Answer
Is the set new in the box, and never opened? Is it retired and rare? In that case, the skies the limit since the set may not be available anywhere. When I find my self in this situation I generally list for the high-end price on brickpicker, but include a best offer option.

Do you have the manual, the box it came in and all of the parts and minifigures? Then head on over to brickpicker.com and look up the trending used prices on the sets you want to sell. Use this information to sell the item on ebay (but be ready to pay Ebay 15% of your sale price right off the bat!). You can also try to sell locally, but you will have a hard time finding anyone willing to pay your asking price for what they will consider old used lego.

Is the set complete, but you have no box? See above, but adjust your asking price.

Are we talking about a collection from your childhood that is in a tub in your parents garage? An unsorted lot? A bunch of 'sets' of undetermined completeness? Aim for $10 per pound, but accept $5 cause it sounds like you may be in a hurry.

-Brian
> 3 votes

# Answer
Can I suggest you also other ways like selling your sets on http://oldlego.com or promoting your selling on big Lego forums like http://eurobricks.com
> 1 votes

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Tags: star-wars, trading
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# Question
Title: Is there a good way to buy molded LEGO boxes?
I'm considering some new storage options, and there are some official LEGO boxes that I'd like to use as they already fit in my existing shelving system. The following sets contain the boxes that I'd like to use:

I wouldn't mind picking up a few copies of the classic brick box for the parts, but I'm less excited about the others. I'd like to get a variety of colors of these boxes, and they aren't widely available on Bricklink.

Is there a good way to get these boxes without buying several copies of each of these sets?

# Answer
> 1 votes
I have considered this as well as the boxes look nice and they are stackable. However after taking into consideration how difficult it was going to be to acquire these boxes in sufficient quantity, be able to expand the system as my collection grows, and the fact that even the largest box is quite small, I decided against it. It is just not worth it.

Also, the boxes are not really practical for storage. They are narrow and deep, meaning it is hard to find pieces. I prefer wider and shallower containers where it is easier to see what's inside. It is best to go with a generic storage system readily available at department stores. They are made to be practical for storage, they are cheap, and can be expanded as your collection grows. If you would like to have the LEGO-ish look, you can always paint your shelves in bright colors, add posters, LEGO stickers, etc.

However if you really-really want these boxes, you might want to team up with eBay or BrickLink sellers who don't really care for the boxes but sell the parts. Try to reach out to larger sellers who buy sets in quantities, so you can get a number of boxes at a time.

# Answer
> 0 votes
I suspect that cheap quantities of the duplo box will be hardest to find since virtually all who buy it will be buying it for small children and will probably keep the box to store the bricks. Also, it probably wouldn't occur to anyone that there might be resale value to the box itself. These boxes will likely end up getting played with until they're too beat up to use as nice display boxes, and/or will end up in a recycling bin somewhere.

Depending on how determined you are to get these boxes, I'd see if you couldn't find a toy store that would let you post a notice near the duplo boxes stating that you're willing to buy them, or that would pass your contact info to customers who buy a box. Failing that, I'd buy a pile of the yellow ones and paint them.

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Tags: shopping
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title: Brick Compendium: BIONICLE LEGO

text:
# Question
Title: Brick Compendium: BIONICLE LEGO
Is there a comprehensive compendium of the old Bionicle pieces?

For example, what is the part name for:

* Tahu Mata's flame sword?
* Lewa Nuva's twin blades?
* The Zamor Sphere's holder, as used by the Toa Ignika?
* The Midak Skyblaster?
* The zipcord whirly-peg thing for the spinners?

# Answer
You will find most LEGO pieces, including those that are specific to the Bionicle theme on Peeron. For example here are your particular mentions:
> 4 votes

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Tags: part-identification, bionicle
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# Question
Title: Which combination has a lower gear friction?
I need roughly a 1:3 reduction and I see a couple of ways to achieve it:

* using a 8t gear and a 24t gear (1:3)
* using 2x 12t gears and 2x 20t gears (1:2.779)
* using a 16t gear and a 40t gear (1:2.5)
* using a 12t gear and a 36t gear (1:3)

Now, size issues aside, and assuming all axles are held by at least two beams, how do these combinations compare as far as wasting the least amount of power due to friction? What about torque? (where the 8t gear may have an issue)

This is for a high-RPM, low torque situation, so I am not exactly super concerned about backlash or torque forces, just efficiency and friction.

I would be open to other gears as long as the reduction is in the same rough ballpark as the aforementioned, especially if it's more efficient somehow.

# Answer
According to Sariel's gear tutorial in chapter 5, Efficiency:,

`- the less gears, the better
 - the smaller gears, the better`

Based on this principle the first setup looks the best, but you are right that the 8 tooth gear is the weakest of all and it has the most backlash too, if any of these are valid concerns for your build.

Note that gears can be strengthened by using them in parallel by putting some 24 tooth on one axle and the same number of 8 tooth on the other, mating them together all at once.

If you are concerned by backlash, you can experiment with springs, rubber bands or other ways to put a constant load on the system.
> 7 votes

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Tags: building, technic, gears
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# Question
Title: My building is developing gaps and spaces
I am building a large project, and there are spaces developing between bricks and plates. I've been working on it for almost a year, and some places are 20+ bricks high. What can cause this over time? Can plates get soft and warp? If the weather is warm, can this affect it? Has anyone else had this problem? Also... As many times as I've undone and re-done sections, some places won't level out and can be less than one plate off in height.I would love some advice. Thanks!

# Answer
Without more information, it's hard to know what can be causing the gaps. My theory is that the structure has gotten large enough that the spacing in the bricks is adding up such that your structure is no longer "square".

According to this page, there is a 0.1mm gap between two bricks attached to a common base. This gap makes it possible to remove the bricks once they've been placed. Also, Lego claims their manufacturing process has a tolerance of 0.01mm (10 microns). With a long enough structure, those mm add up.

Here is an example of the gap in play

There are the same number of plates on the left and on the right. The left ones are all pushed together, the right ones are attached to a baseplate (or some other 16-stud plate or brick). Because each plate has a 0.1mm gap, multiplied by 16 plates gives 1.6mm difference. Even if the 0.1mm isn't the right value, you can see that there IS a gap and it is large enough to be significant over a small distance.

When you are building a very large creation, inevitably some things won't want to fit properly. I am building a multi-story building using 1xN bricks for the walls (mostly 1x2 and 1x4 bricks). Each story is the same size as the previous one, and each one is re-inforced by the flooring and internal walls, but it's painfully obvious that the different stories don't fit well together. When I take one story off another, it doesn't want to snap back into position later.

It's even possible to take advantage of the gaps to make curves. If you make a long enough wall out of 2x1 bricks, you can physically bend it into a circle.

As far as advice on how to avoid this problem, I don't really have anything concrete. One thing you could try to do is to space things uniformly, using the same kinds of pieces all the time. If you build a long strip using 2x4 bricks on one side, and 2x2 bricks on the other, you may find that they are not the same length even though they have the same number of studs. Or, design your creation in modular sections, counting on the fact that it will not quite meet at section boundaries. This is how people build bridges: they are frequently designed to allow for expansion and contraction of the bridge sections by placing seams that allow for the change in size as the bridge temperature changes.
> 1 votes

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Tags: building
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# Question
Title: How exactly does the pull-back motor (12787) work?
I've got the 42034 Quad for my birthday and it's been really fun to play with technic after so many years.

I am very curious about one thing, though - how does the pull-back motor (12787) work and look internally? I'd unscrew mine but I am afraid I'd damage it.

I am guessing it probably uses some kind of spring and/or rubber bands to build the pressure but I'd love to know it's internals precisely.

# Answer
> 7 votes
Another type of pullback motor has a detailed structural disassembly here: Imgur album.

I think your motor should work mostly the same way, but I wasn't able to source such internal pictures.

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## LEGO Micro Pull-back Motor Reassembly

Micro Pull-back Motor Parts

Gear A: Pin shaped like 'E' for attachment to Spring on Chassis Gear B: Smallest (of 2) gear with a pin Gear C: Largest gear with 2 levels, smaller gear at the bottom, larger gear on top, with teeth for meshing with Axle F Gear D: Smallest (of 2) gear with a hole Gear E: Medium gear with 2 levels Axle Assembly F Gear Assembly G

Not shown: 5 X-head screws Note: Gear A may be detached from Spring. I attached it such that it won't fall out when flipped upside down.

Install Gear B Place Gear B with pin downwards into slot in Gear Assembly G

Install Gear C. Place Gear C into the hole in Gear Assembly G. The larger gear is on top. Gear C will cover Gear B and mesh with it (though Gear B has some play since it is in a slot)

Install Gear E. Place Gear E into the small depression in Gear Assembly G. The larger gear is at the bottom, and will slide under Gear C. There is a pin facing up. Gear E will mesh with Gear B.

Attach Gear D to the Axle Assembly F. Gear D has a small hole which fits on the pin on Axle Assembly F.

Attach the Axle Assembly F to the Gear Assembly Cover G. Flip the Axle over. Gear D should stay attached to the Axle Assembly. Align the Axle Assembly and snap down on the protruding pin on the Gear Assembly. Pinch the two parts (F & G) together at the lower section using thumb and index finger, and try to spin the axle. The gears should only rotate when the axle is spun in one direction, and not the other.

Reattach the Gear Assembly G to the Chassis. This step is tricky. You will need to pinch the Gear Assembly to keep parts in place, then place the Chassis on top of the Gear Assembly G, and move it around until Gear A connects with the correct hole and mesh with the other gears. Then, holding everything tightly, flip it over, and start installing and tightening the screws in a diagonal pattern. Don't over tighten the screws, you should install at least 3 screws first (one on top, two at the bottom), and test that the spring is engaged with Gear A and you get a pull back action when the wheels are turned. After that, install the rest of the screws and tighten all of them.

The pull back action works, but I can't figure out how to fix the torque on the spring. So the car is no longer a race car but a jalopy!

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Tags: piece-information, technic
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# Question
Title: Does knolling help or is it just part of the fun?
When building a new set, many people knoll their LEGO bricks before beginning the assembly.

My question is: Is there a actual advantage to knolling all the pieces or is it only a way to stretch the fun?

It seems to me that if the main advantage is to save time when looking for the pieces, knolling nullifies this by demanding an enormous amount of time to pre-organize all the pieces.

# Answer
Knolling is organizing objects by type, at right angles.

If you enjoy spending your time doing that, then by all means, do it.

However, logically, it is obvious that precisely organizing objects provides no benefit to anyone whose mind doesn't require strictly rectilinear organization of objects.

1. First, you have to sort all the objects (in our case, lego pieces) by type and colour.
2. You have to precisely arrange them.
3. Then, you build something, using up those pieces you just placed so precisely. Presumably you'll knock some askew: do you re-knoll? Do you have to move slowly and more carefully to avoid accidentally knocking them around?
4. By the time you're done, you're left with a creation, and a small number of knolled spare parts, now no longer in any kind of suitable arrangement (due to most of the parts being put on the model.

Or, consider the other scenario: 1. You just open the bags of parts and pick from the bags (or, as I do, you dump the bags into shallow containers, so that it's easier to see and grab parts, but you don't mix all the bags together. 2. When you're done you have a bunch of empty containers.

The advantage to the 2nd way is that you don't have to spend any time categorizing and sorting parts. You just grab what you need.

The only practical advantage to knolling is that you can easily see where parts are, and grab the appropriate ones. You can even count them and compare against the set's inventory to see if any are missing. However, you can achieve the sorting goal without knolling, but rather just by separating the parts by type and colour. This is faster, because you don't waste time fastidiously placing things at right angles.

For most Lego kits, I'd argue that even sorting the parts is a waste of time, because the parts are generally not randomly placed in bags. Even if the kit doesn't have numbered bags for different stages of the build, the pieces are not randomly distributed between bags and so you can still easily find things. (If someone else is sorting for you as you build, THAT can save time, but it requires two people, and thus doesn't really save time overall).

When building from your collection, if your collection is sorted (as mine is), knolling or otherwise arranging parts is a big waste of time. It's fastest if each bin of your collection has one type and colour of part and the bin is large enough to hold the pieces loosely. If (as I do) you run out of space for loose parts, you can save space by attaching the pieces together, or fitting them in tightly like a puzzle. This takes an enormous amount of time and, furthermore, wastes time later when you take the parts out to build. The only reason I put up with it is that I don't have unlimited budget and storage space to buy the bins I use for storage.

TL,DR: knolling is organization taken to extremes. It's based on aesthetic principles and not efficiency. What efficiency it gains can be had for lower cost by simpler organization methods. If you enjoy knolling, go ahead, but it certainly isn't really *helping*. If you can't stop knolling, you might be OCD.
> 5 votes

# Answer
I would say it's helpful *and* part of the fun.

I don't do it very often, but I know I did it for the diorama Death Star 10188.

Most sets aren't big enough for me to want to do it though.
> 4 votes

# Answer
I generally only build sets of 1000+ pieces and I find knolling incredibly useful (as well as somewhat relaxing but YMMV on that). Where I find that it helps the most is familiarizing myself with all of the pieces that will be used in the next set of instructions. Sometimes it is easy to misidentify a piece from the images in the instruction book. So for example if I know ahead of time that there will be 1x2's in 3 different shades of gray, when I see one in the instructions I now know to carefully choose which one is intended.
> 3 votes

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Tags: building, knolling
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# Question
Title: EV3 Error and VM Program Instruction Break
I'm making a program which is very complex and large but it does not contain any Arrays in it. Weird thing is, last night it worked fine but today when I downloaded the exactly same thing into the EV3 it shows a triangle with exclamation mark symbol with orange status light.

This happens halfway when it tries to run a switch with a Logic Variable. Occasionally I would get a "VM Program Instruction Break". Any idea how can I solve this?

# Answer
**UPDATE: It turns out there was a compiler issue in the EV3 desktop programming software. LEGO has released a fix in v1.2.2 of both the Home and Education versions. Upgrading your software will fix this problem.**

Read more about the problem and the fix in this pdf from the Seshan Brothers.

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ORIGINAL ANSWER:

Some suggestions from the LEGO MINDSTORMS EV3 Facebook group:

1. Too many named loops in your code
2. Too many blocks in a loop
3. Try to avoid using too many loop interrupts
4. A problem with the copy/paste - delete the pasted portion of the program and make it from scratch
> 2 votes

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Tags: mindstorms, technic, lego-group, ev3-g
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# Question
Title: EV3 - At what time DIRECT_REPLY is sent by brick?
For example: I've sent DIRECT\_COMMAND\_REPLY to rotate the motor for 720 deg. When EV3 brick should send reply:

1. before motor finished rotation (right after my command was received) or
2. after motor finished rotation?

Now, I have feeling that reply is sent right after my command was received by EV3 brick.

# Answer
> 1 votes
I have the same observation as you, it seems to be sent as soon as the brick receives the command.

A workaround that I have found is to send a "stop motor" command after every movement, this way you know when the motor is stopped for sure.

Out of curiosity, what library are you using?

EDIT:

Have you been capturing the packets that the EV3 sends back to the computer?

# Answer
> 0 votes
The DIRECT\_REPLY is sent when all of the operations in the DIRECT\_COMMAND are completed. (Side note: you can have more than one operation in a direct command).

So the better question might be "when does the motor rotation operation complete?". It completes immediately and moves to the next operation in the direct command. This is why you get a reply before the motor movement is completed.

You could try appending opOUTPUT\_READY to your direct command to see if it will delay the reply.

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Tags: ev3
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# Question
Title: need help identifying which set these 3 bags are from
I ended up with three lego bags but need help identifying them. mostly light grey and dark grey with some blue and burgundy. The bags say 2011 lego on recycle symbol. There are two clear half spheres as well as a plastic ring 4580665

# Answer
> 3 votes
The two black sprocket wheels and the transparent dome from bag 4 suggest that this set is the Malevolence, but many easily identifiable parts are missing. However, your set also seems to miss at least a few bags (numbers 2 and 3), so it is highly probable that you have a partial set.

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Tags: set-identification
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# Question
Title: What is this snapping brick for / which set is it from?
I've found this DUPLO brick:

The red part can be pushed in and snaps out when the button on the top is pressed:

Any idea which set this is from or what it could be used for?

# Answer
> 7 votes
Looks like the Duplo Car Launcher and according to Bricklink this appears in at least 4 different sets: http://www.bricklink.com/catalogItemIn.asp?P=31080c01&in=S

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Tags: part-identification, duplo
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title: How much does a LEGO brick weigh?

text:
# Question
Title: How much does a LEGO brick weigh?
I am trying to do a science project and I need the exact weight of one of the LEGO pieces. I am using it as a counter balance on my scale. What is the weight of a 1x4 LEGO brick?

# Answer
In most cases you can find the weight of a brick from Bricklink an unofficial LEGO site that takes weight measurements from user submitted data. Bricklink states the 1x4 brick as 1.64 grams in weight.

LEGO bricks tend to be odd weights because the design process primarily focusses on the physical aspect. A 1x8 and 2x4 brick both have exactly eight studs, yet the weight between them differs by almost a gram.

In the interest of scientific accuracy, I would recommend weighing the bricks yourself with digital kitchen scales to confirm the weight.
> 23 votes

# Answer
*"How much does a LEGO brick weigh?"* is a seemingly simple question, but the answer quickly spirals into complexity.

I work with many hundreds of identical bricks fairly often. To count these out accurately I use high precision scales (0.01g), but I'm never confident about the counts.

Be aware that as well as **variations in mold design** (which other answers have pointed out), even pieces from the exact same place on the same mold can have different masses. **Different colours** of LEGO have different densities, so even for the same volume of plastic you'll get different weights.

I commonly come across sets with two different moldings, for example with the rods in the underside of bricks being hollow or not. The reason for this is that mold designs are changed when designs with better characteristics - typically plastic consumption, but possibly heat dissipation, flow attributes or other factors - are created. But manufacturing a mold costs a vast amount of money; the most expensive ones are over a quarter of a million dollars. Because of this large capital cost to produce molds, LEGO manufactures elements from **different mold designs at the same time** (plastic molds can be good for 10 to 250 thousand impressions, and might be refurbished rather than retired an the end of this run) and you have a world where your question can't be answered definitively.

Here's the best advice I can offer:

1. weigh many identically-coloured bricks on a high-precision scale\*
2. before you do, inspect each brick to ensure that there are no mold variations
3. divide the total mass by the number of bricks

**I have a kitchen scale that has 2 grams of precision, and a much smaller scale that works to 0.01g. Which is more precise? More accurate? How can you make one give more precise answers than the other?<br>If you go more precise that than 0.01g you're going to have to protect against noise introduced by fluctuations in air pressure (as it is, I have to be careful not to breathe on the 0.01g scales or the reading bounces around for a while). If you go to a jeweller's shop, you can see how they deal with this problem when they weigh gold and gems - they put a hood over the scale!*
> 7 votes

# Answer
Since it is for a science project, I would suggest you take the official weight and compare it to the weight you come on your own. This will not only get you your weight but will score your project higher. The best way to do this would be to take 100 pieces and weigh them on a postal scale (if your school doesn't have access to one, your parent's work might, or even the post office might do it for you). Then take the total weight and divide it by... 100!

Of course the more blocks you use the more precise your weight will be, but after a while it just get to be silly...
> 5 votes

# Answer
I have a 1x4 brick that weighs 1.7grams. My scale measures to the nearest 0.1gram. A 1x4 plate (one third the height of the brick) weighs 0.7grams. Together they weigh 2.3grams, so the actual weight of each part is likely 1.65 to 1.70 grams and 0.65 to 0.70 grams respectively based on that. These were standard parts, I don't think that the color will matter within the measurement accuracy, however, a transparent part is made from a different material and will likely be different.

I also grabbed 4 1x4 (standard, nontransparent) bricks at random and collectively they weighed 6.4grams. I made sure that they all appeared to have the same type of mold. I found one that had small depressions on the tube side (likely for mold venting) and excluded this (it weighed about 0.05 to 0.1grams less than the others). So this suggests that this particular type weighs, 1.6 grams on average. I'm not sure what the expected variation would be, but with a little statistics you could figure out how many you would need to measure to get a most likely value. For your purposes, I recommend that you use 1.6 grams if the three tubes do not have a depression on the end (and 1.5grams if they do) and if you need to know better, take some measurements yourself (of the actual parts that you are using).
> 2 votes

# Answer
LEGO Scale (approximately 1:40)

```
1 stud     =  .318 in (~5/16 in)
3 studs    = 0.95 in
4 studs    = 1.27 in.
3.18 studs = 1 in.
11 studs   = 3.5 in.
16 studs   = 5.09 in.

```

Dimensions = .96 cm ht x 3.2 cm length x 1.6 cm depth. To scale real world weight to 1 Minifigure (MF), multiply pounds (lbs) by 0.0067, tons by 13.33, and kilograms (kg) by 0.0147.

*As a rule, pack animals can carry 20% of their own weight comfortably without tiring. Plastic animals may be similar... but I digress.*

To get a really good measurement, it helps to weigh a lot of bricks (of obviously the same type) at once, say 100 pieces of 2x4 bricks might yield a weight of only half a pound. *But it sure feels like a lot more, after you include the little bags, the cardboard box, the receipt from the store where you got it, that old ring nobody wants, sorry! Won't happen again.* Hope this was helpful.

Weight of Bricks

```
1x1: 0.4g   (0.13 MF)
1x2: 0.78g  (0.25 MF)
1x3: 1.17g  (0.38 MF)
1x4: 1.57g  (0.51 MF)
1x6: 2.25g  (0.72 MF)
1x8: 3g     (0.97 MF)

2x2: 1.18g  (0.38 MF)
2x3: 1.71g  (0.55 MF)
2x4: 2.22g  (0.71 MF)

2x6: 3.5g   (1.13 MF)

```

Also, for those interested: What's the smallest piece of lego? Lugnut says it is a gold coin, weighing in at just over 0.056 g; the flower petal is a hefty 0.064 g. For reference, a 1x1 plate is 0.176 g, a 1x8 brick is 3.06 g, and a Minifig with no hat/hair or accessories weighs 3.11 g.

The official LEGO scale is (presumably) 1:40. At this scale a Minifig represents a person 5' 6" tall and 2' wide. *No, sweetie, you look fine like that. Very thin and pretty! Ahem.*

A 1" square represents 3 1/3 scale feet (40 inches)

Just for fun, ever wondered how far a Lego mile would be? Only 110 feet, not much more than the distance to your neighbor's house! Next time I'll calculate a Lego Light Year *and possibly a Light Sand Year, as well. a hee-hee a hee-hee I am a sad, corny ridiculous nerd!*
> 2 votes

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Tags: piece-information, weight
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# Question
Title: What Technic vehicle is this in black and red?
Any help with the set this piece is associated with, would be appreciated.

# Answer
I did a cross check on sets containing following pieces 'red-42003', 'blue-6632' and 'black-32250'. This looks like the B model for set 8065.
> 6 votes

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Tags: technic, set-identification
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title: Purchase a list of LEGO parts

text:
# Question
Title: Purchase a list of LEGO parts
If I have a list of LEGO parts (exported from LEGO Digital Designer or Bricksmith) is there an easy way to purchase all of the parts either on LEGO's Pick a Brick or on Bricklink?

I know that I can go through the list one by one and order the pieces but I was hoping that there might be some tool where I can upload a list and have all of the parts automatically added to my cart.

# Answer
> 4 votes
Doing this for Pick-a-brick (which sports an antiquated UI) requires some fairly advanced hacking. See this question. It's unfortunate that there is no simple interface for importing composite sets of bricks.

# Answer
> -3 votes
With bricklink you can convert to xml with ie ms Excel

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Tags: shopping, pick-a-brick, bricklink
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# Question
Title: Batman Arkham Knight Batmobile Instructions
Where can I find a set of instructions for the Lego Batman Arkham Knight Batmobile?

# Answer
The author of this Ideas project might be able to give you a copy of the instructions for his model.
> 2 votes

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Tags: instructions
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title: When was the RCX 2.0 released?

text:
# Question
Title: When was the RCX 2.0 released?
I know that the original RCX was released in 1998 and the NXT was released in 2006, but when was the RCX revision 2.0 released?

# Answer
According to Brickset and Peeron, it was released in 2001.
> 2 votes

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Tags: history, rcx
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title: Vintage heads still in production?

text:
# Question
Title: Vintage heads still in production?
Are vintage Lego heads with the classic grin still in production?

I am having trouble deciding whether the head-with-grin piece (element ID **9336**, called "MINI HEAD NO.1") which is produced today (and available in the Bricks and Pieces online store) is *100% identical* to the classic head used in the 70s, 80s and 90s. If not, what's the difference?

Visually I think it looks the same, but it appears that 9336 is not the code used for vintage sets.

# Answer
> 4 votes
Yes, visually the simple smileys are the same now as in the past. The difference is in the stud. Some have a stud like what you have pictured above; with an open stud and others have a solid stud. Other than that, the face itself is exactly the same. You can three all three versions of the stud here (solid, recessed open and recessed blocked) here: http://www.bricklink.com/catalogList.asp?pg=1&q=standard+grin+pattern&catLike=W&v=2

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Tags: piece-information, minifigures
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# Question
Title: Use for "Technic Coupling, Tight" and "Technic Coupling 3,5-6 Ncm"
Power Functions set 8293 contains these pieces http://brickset.com/sets/containing-part-6025005 http://brickset.com/sets/containing-part-6036892 and they make the set much more expensive than just buying the other parts in the set individually. By that reasoning these parts must be very special, but I can't tell what is different about them from the images compared to a regular gear wheel.

# Answer
This gear can only handle a certain amount of torque. Above this torque the gear starts to slip internally. This pervents damaging the motor when the some part of the construction after the gear gets blocked.

Lego uses these gears ofter in constructions where there is a end of stroke that blocked the motor from turning, for example a winch or other string based designs
> 5 votes

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Tags: piece-information
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title: Color Sensor/hi-tech and EV3

text:
# Question
Title: Color Sensor/hi-tech and EV3
I want to create a line follower by EV3 using hi-tech color sensor without using switch! :( I tried some former ways but the robot cannot follow the line very well! can anyone guide me?

# Answer
> 1 votes
This is from page 87 of a document showing how to run NXT bricks using EV3-G software.

It uses the light sensor, not color sensor. You'll want to set the mode of the color sensor.

Inside a loop that will stop following a line if the left button on the brick is pressed.

Basically, the steering value of the motors is taken from the light sensor reading.

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Tags: ev3
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# Question
Title: pc program to receive data from EV3 via usb/bluetooth
I'm looking for a library to create a desktop program. It should receive a data from EV3 brick programmed by standard EV3 software.

Currently I consider 2 approaches: 1. EV3 brick sends a bluetooth message, PC receives it. 2. EV3 brick creates a file and writes a data to it, PC reads the file via USB.

It's more convenient for me to use USB because bluetooth is already used to connect to another brick.

I found 2 libraries how to do that, although there are obstacles:

* monobrick C++ library \- allows to read a file, but doesn't allow to connect to the brick via usb
* Microsoft EV3 API \- allows to connect to the brick via usb but doesn't allow to read a file

# Answer
> 2 votes
The MonoBrick C++ library that you linked is for NXT, not EV3.

You can find the MonoBrick C# Library for EV3 here. It works with USB, Bluetooth and Wi-Fi and can manipulate files.

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Tags: ev3, bluetooth
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# Question
Title: How to measure green/blue reflected light on EV3?
As I know there is no way to turn on green/blue reflected light on EV3 color sensor.

Is there a way to do it using NXT color sensor and EV3 controller?

Or the only way is to use NXT controller together with NXT color sensor?

# Answer
> 2 votes
There is a modified Color sensor block available here.

As of this writing, this is the most up-to-date direct link to download the block.

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Tags: nxt, ev3, sensor-colour
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# Question
Title: Have Multiple Inputs to Programming Block
Originally, I had a simple program to move until the robot hit a wall, then it reversed and turned and moved again, repeated to infinity. It works by turning the motors on, waiting for input from the touch sensor, then reversing, turning, and continuing. Now I want to add a second wait on the touch sensor to trigger the reverse and turn sequence, but I can't add two different ports to wait from, or have two different triggers to start the reverse and turn. Is there any way to have a trigger from two different wait inputs?

# Answer
> 2 votes
You can do this with parallel programs and a logic variable. You will need 3 loops, one for each sensor and one for the motor. In the sensor loops, wait for the touch sensor to be pressed and then set a logic variable to true. In the motor loop, have a switch block that tests the logic variable. If it is true, reverse and turn around and then set the logic variable to false. If the logic variable is already false, just go forward.

# Answer
> 2 votes
Here is another pattern that watches more than one sensor. Instead of parallel code blocks setting a variable value, this code combines sensor outputs to feed a logic block which feeds a switch. No variable is used.

Note that only the touched side of the switch statement is used. Not an important difference, I just find it easier to follow.

The other pattern might be described as event driven, which is used widely in programming.

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Tags: ev3, programming, ev3-g
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# Question
Title: Will playing with a 12V train motor by hand damage it?
This question is similar to one for PF motors.

The 12V motor bogie has considerably more resistance than does the newer PF bogie motor, which may be moved very easily when not operating.

So, if one pushes a 12V-motorized train by hand, will it cause damage to the motor?

See title "Set 7865: six wheeled Lego® train motor (12V, 1980 - 1990)" on this page for the specific motor I'm referring to.

Side note: I've noticed that the connected headlights in the train don't illuminate when pushed by hand (and have asked a question specifically in regards to this).

# Answer
> 5 votes
As you can see in the picture below the friction has to do with driving the worm wheels via regular gears while pushing the unit by hand and yes, I guess the gear teeth on the wheel axles could be damaged because of the gear ratio.

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Tags: motor, trains, 12v
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# Question
Title: How much do you think these Lego pieces are worth?
I've got some very old LEGO brick from the 50s, and am wondering how much they are worth. I'd like an estimate because I know that they are now collectors items that might be worth something.

Here are some of the items:

* Three Lego Beetles that are in plastic very good condition in red black and grey
* A plastic red fire truck and a tanker that is red with written "Esso" on it and other small size Lego plastic trucks
* The Lego set 810 with all the items inside
* Another big wooden box of Lego
* Box number 750 containing some architectural buildings

Instructions are included with each box.

# Answer
My answer to this kind of question is always "it's worth exactly as much as someone is willing to give you for it."

That said, one could look up prices on BrickLink (assuming there are any for sale there) and go from there. Failing that, put them on eBay with a reserve/starting bid of whatever minimum amount would make it ok for you to part with them.
> 4 votes

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Tags: shopping, lego-group, value
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# Question
Title: What prevents a 12V motor, when pushed by hand, from providing DC electric out?
This question is somewhat related to a similar question I asked about whether pushing a 12V train motor (such as the one below) would damage it.

See title "Set 7865: six wheeled Lego® train motor (12V, 1980 - 1990)" on this page for the specific motor I'm referring to.

Irrespective of whether damage occurs to the motor when being pushed, I'd like to know why, given it contains a DC electric motor, when the gears are pushed by hand, electricity isn't generated by the motor in order to provide current to any connected load (e.g. the lights on the train).

I've noticed that the connected headlights in the train don't illuminate when pushed by hand -- is there some sort of electronic protection to prevent it being used as a generator?

# Answer
The 12v train motor uses 2-pole 3-slot technology.

Because of thinner, but longer wire which results in a greater resistance and will create higher voltage, but lower current the current output isn't enough to drive on-train lights. Since the resistance of on-train lights is constant this will drag down the generated voltage as well.
> 7 votes

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Tags: trains, motor, 12v
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# Question
Title: How can I power my LEGO pneumatic engine?
I have just finished building a simple LPE, but have no means to power it. I live on a farm and have access to a small air compressor, would that work?

# Answer
> 4 votes
Since the compressor produces compressed air, it would certainly work, given you build adequate fittings and take precautions against overpressurization.

LEGO pneumatics have been tested to withstand as much as 8 bars or 120 psi, but you definitely should plan with safety margins. If your compressor can produce higher pressures, I'd suggest building in some kind of release or auto-shutoff valve to prevent damaging the LEGO parts.

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Tags: pneumatic
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title: I need an NXT motor adapter

text:
# Question
Title: I need an NXT motor adapter
I'm trying to get an NXT motor adapter to this that I'm getting:

If you don't recognize this, the parameters said : 80mm

2000 ±10% RPM 28.89 CFM

Rifle

20.9 dBA

Please tell me what this is called so I can look for it.

# Answer
> 2 votes
The adapter itself is generally called a "Molex" adapter. The one you have pictured looks similar to their Mini-Latch style.

I would recommend an adapter like this. The pin spacing should be the same even if it is not made specifically for that connector.

The red wire connects to pin 1 and the black wire connects to pin 2. The yellow wire is for speed feedback, but it won't do any good unless you modify the NXT firmware, so I would leave it detached.

Alternately, you could cut a NXT cable and solder it directly to the fan wires.

Also, you didn't say, but the fan is probably 12V and the NXT can only supply battery voltage, which is only at most 9V with fully charged batteries, so it will run slower than it does when connected to a 12V power supply.

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Tags: nxt, motor
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# Question
Title: Why can't I combine a EV3 Motor with a Technic frame in LDD?
It is easy and stress-free to attach a frame to a large motor in a vertical or horizontal manner as shown in the picture in real life. But I can't do the vertical version inside LDD. Anyone knows why?

Is it be because the cross-section of the beam of the frame is not a mathematically perfect square? But I can actually do the following test model in LDD. The yellow and red technic beams have different orientations. The picture is a snapshot of four views of the same test model in LDD. (LDD did close by itself without any message/trace several times when I try creating the model! Very frustrating!)

I created a vehicle with a frame attached vertically to a motor. I like to document the process. Can anyone suggest a way to get around the 'restriction'?

The two parts are 95658 and 64179.

# Answer
I slid the Technic frame over an axle instead of a pin to see how far it would go. As shown in the picture below, it appears as if the part is too big to fit all the way because the rim (shown level with the red line) is too thick.

LDD runs a basic collision detection to ensure that no parts overlap. In real life, certain combinations of parts are impossible without stressing the bricks.

The combination of EV3 Motor and Technic Frame in real life have a very, very small amount of friction, so it shouldn't be harmful. But LDD has no tolerance for overlapping parts.

You do have several options:

* **Edit the LXFML file**. This is the most technical soloution. Export the LDD file as a .lxfml file as opposed to the standard .lxf. Using a text editor on your computer (such as notepad) you can directly adjust the co-ordinates of the pieces to overlap. However, If you do move the parts apart, you will need to manually put them back together by editing the file. You can find more about LXFML here.
* **Different Parts.** Use different parts that perform the same function as the Technic beam, or don't include the part at all.
* **Other Software**. You may find it easier to build your model in other LEGO CAD software packages such as lDraw. It should be possible to export your model as it is now and import it into most LEGO CAD applications.
> 4 votes

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Tags: ev3, technic, ldd
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# Question
Title: Information on this large beige motor w/battery box?
I have a LEGO Technic motor with a built in battery box for x3 "AA" batteries (thus 4.5 volts). Could you help me identify it? What set does it belong to and how old is it? Colours are beige and green/grey. Has a red light on top and a white round brick which serves as a control switch. There is a on-off switch at the base, and the numbers 3393 are found at the base.

# Answer
It's the main module from Record and Play (set 4095):

This part was only included in this set released in 2003. The part contains several motors and some electronics that allow you to record motor movements and then play them back.

Pressing the red button would let you record movements for a maximun of 20 seconds by adjusting the motors and the green button would play back the last recorded movement.
> 11 votes

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Tags: part-identification, motor, creator
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title: Neutralize brick scent

text:
# Question
Title: Neutralize brick scent
I store some used Lego sets in household plastic boxes originally used for candy. I thought they were ideal, but now I found out the bricks have caught an unpleasant candy scent -- despite cleaning the boxes thoroughly.

After having washed the pieces *several times* with water and mild detergents, the same smell is still there. What can I do?

# Answer
I've read that vinegar or baking soda (but not both at the same time!) can remove scents. If I were you I'd start trying with the baking soda, since the vinegar itself has some odor.

Activated charcoal is used in industrial scale to filter and purify, you could try that too, it is less trivial to get hold of and probably stains the bricks but it can be washed off by water.

A friend of mine used to clean her LEGO bricks by sewing them tightly in a blanket and putting them in the washing machine with the appropriate amount of detergent. If you choose this method, make sure to always stay clear of the melting point of ABS (80°C or 176F), leaving a margin for security. 50°C or lower shouldn't cause any problems

The simplest solution though is probably to allow the bricks to let out their smell by exposing them to fresh air, maybe accelerated by a fan or such. Beware though, if the candy smell implicates sugar residue it can attract insects.
> 3 votes

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Tags: cleaning
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# Question
Title: What is the easiest option to start making instructions?
I'd like to make instructions for my kids, which they could read either on paper or on a tablet.

What is the easiest option to achieve that, ideally using open-source software (and running on Linux)?

# Answer
> 7 votes
After testing several software (and figuring out quite a few are not compatible with each other), I tested Leocad, and was able to easily create models and generate instructions.

In Leocad 0.82, going through "Print Preview…" and then printing to PDF generates simple and clean instructions.

http://raphink.github.io/lego\_models shows the results I got with that method.

# Answer
> 6 votes
## Take pictures!

The easiest way is to take photographs of each step as you build. No special software is required, you can just step through each building stage by flicking through photos.

If your tablet has a camera you will have everything you need to create and view the instructions. You might want to include which parts you need for the next step in the previous slide.

I don't know a lot about Linux, but if you have access to word processing or image editing software you can combine multiple steps on to one page and print them.

**Flickr:** LEGO Shaun the Sheep (Version 2). Teabox (henrik\_zwomp).

Build your model on a background that contrasts the model, in most cases white is perfect (unless you're building clouds or sheep). If you have a camera, it would help to use a tripod to keep the camera in a fixed position and your hands are free to build.

# Answer
> 2 votes
The best software for this is the Lego Digital Designer (LDD for short) but it is not available for Linux by default. Users have mixed results when trying to run it by WINE or using virtual machines.

There is another recommendation, which requires more manual work though. It uses Lego Instruction Creator (LIC), but it is a stagnant project and was buggy even back then, not sure how would it work in modern environments.

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Tags: instructions
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# Question
Title: Selling custom LEGO image mosaics using original LEGO bricks without breaking LEGO's Fair-Use Policy
**We have designed software and an accompanying site to convert images into 48x48 (or larger) LEGO mosaics**; we use the current LEGO color palette, use image dithering to improve color availability, since the LEGO palette is rather limited (an example of dithering: putting red/blue blocks in a checkerboard pattern creates the illusion of purple at a distance), and finally improve the coverage of regions of the same color by using clustering to cover such regions using, e.g., 2x2 or 2x4 plates instead of only 1x1 plates (since, for example, a 2x4 plate is cheaper than eight 1x1 plates).

We searched and saw that others have been doing something like this as well, e.g., Brixels and Pic-A-Brick on Kickstarter, but these projects either use monochrome 1x1 plates (Brixels) or don't provide the actual bricks, only instructions (Pic-A-Brick). So our idea still seems feasible.

A **problem** is ordering the correct plates in the correct color per order in a cheap and straightforward way (although this could initially be done through PAB), so we contacted LEGO, explained our idea, and asked if they could provide us with a more straightforward/cheaper way of ordering. To be clear: BrickLink is too cumbersome given fluctuating brick availability/prices and multiple shipping fees when ordering through multiple vendors, and stocking up on LEGO K-boxes is economically infeasible given the "color x plate size" combinations that are needed (each K box only contains a brick of a single size and color).

LEGO's response: **our idea would/could be in violation of LEGO's Fair-Use Policy (FUP), and we might want to talk to an IP lawyer before proceeding**. We don't fully understand this; if we clearly state (at the top of our page and well visible) that our product is not created by the LEGO company, that we are not affiliated with the LEGO company, and that we only use official LEGO bricks (bought, e.g., through PAB) to create our own end product (the mosaic) without using the LEGO logo anywhere, how is that a breach of the FUP? If I build, e.g., a computer using parts of different vendors, I can still sell it as my own brand of computer, as is done by many vendors/computer stores. The same holds for cars and many other machines. How would this be any different from using LEGO blocks as "ingredients" for a product that one wants to sell? Let's make it even more explicit: **Brickmania seems to be doing exactly the same thing**: commercially selling custom LEGO kits (war-related; something which LEGO itself doesn't do) using actual LEGO bricks (no knock-offs) and they seem to be allowed to do so (by the way, they do a good job as far as making clear that their products are not produced by the LEGO company goes).

So it has become quite unclear to us if something like this is or isn't allowed (the initial response by LEGO read as a standard response sent to anyone who might be breaching the FUP - but we somehow doubt if this is really the case for us). **If we make abundantly clear that our product isn't created by the LEGO company and if we follow the rules when it comes to (not) using the LEGO logo, licensed brand names, etc., shouldn't that be enough**?

P.S.

We don't want to use knock-offs and understand that LEGO needs to protect its own brand, but by providing a response like this, we have (ironically) been considering using clone bricks (if possible), while we'd actually like to use quality LEGO bricks that customers can mix with their existing bricks.

# Answer
First of all, if you are serious about this business, go to an IP lawyer who can take this up for you and give you a much more confident answer than the bunch of us LEGO fans can :)

LEGO's Fair Use Policy is located here.

Secondly, you might want to read the perspective in this thread on Bricksetforum. Lots of interesting points of view, and, decent information about what you should be able to show, and what LEGO's claimed and likely actual trademark rights are.

Finally, did you talk with that IP lawyer yet as per my first point? *hint* *hint*
> 6 votes

# Answer
IANAL, and if you're starting a business you should definitely consult with a real lawyer who specializes in IP law in the jurisdiction you plan to serve. However, having read the fair-use policy, I note two things. One, it seems to be focused on trademark issues. In order to be legally clear, you need to brand yourselves accordingly so that Lego's trademarks aren't violated. You will need to become aware of all the trademarks Lego has, and how to avoid violating them. Merely mentioning Lego doesn't violate their trademark. Using their Logo probably does, but that would depend on how it's used and why.

Two, the policy seems to go beyond what trademark law actually requires. For example, they say

> the LEGO trademark should always appear with a ® symbol each time it is used.

I'm not aware that this is a requirement in law. It seems to me it's more like a request they are making, out of paranoia (it seems most businesses are overly paranoid about trademarks). So you might find yourself in a position where you are well within your rights to violate their policy. How mad that makes them, and what effect that has on your business, I can't say.

That said, nothing I know of in law suggests that you can't buy and resell Lego bricks. As you've pointed out, there are many businesses doing just that. That said, there are few places to buy bulk pieces, especially in any quantity you might want for reselling products, and so you might find yourself in the position of needing to deal with Lego directly, in which case you probably have to just do what they want in regards to whatever rules they make up.

Regarding copyrights or patents, the other intellectual property laws you might theoretically run afoul of, you are probably safe with regards to Lego. Since you aren't making new elements (i.e. possibly violating a patented element design) and you aren't copying their set design, box art, instructions, etc, you *should* have nothing to worry about there. You could face copyright issues from the copyright owner of the original image used as the basis for the mosaic, but that's a different story.
> 3 votes

---
Tags: shopping, lego-group, customization, mosaic
---


title: Making an ATM with an EV3

text:
# Question
Title: Making an ATM with an EV3
I am building an ATM using my LEGO Mindstorms EV3, but I ran across a problem. The problem is that I want to be able to input the amount of money that I want to get out of the ATM but I can only have a maximum of three touch sensors because I'm using the fourth for the ability to have a key so my siblings don't steal money.

How can I can make an ATM with a maximum of three input to decide how many 20s, 10s, 5s, and 1s I want.

# Answer
The possible solutions involve realizing that you can multiply the number of possible inputs by implementing long clicks, double clicks, click-and-holds, simultaneous clicks, etc. on the buttons. If I were you, I'd also include a Confirm and maybe a Cancel buttons, but the latter can be substituted by a timeout. You could ease your job if you don't handle the separate bills as individual amounts, but set the requested amount of money and write a function that splits an amount into separate bills (e.g. splitting 58 into 2×20, 1×10, 1×5, 3×1).

With these in mind, have a look at these example button mappings:

Solution #1:

* Button 1: Increase amount by 1
* Button 2: Decrease amount by 1
* Button 3: Confirm

Solution #2:

* Button 1: Increase amount by 1; Long press: increase amount while being held
* Button 2: Decrease amount by 1; Long press: decrease amount while being held
* Button 3: Confirm

Solution #3:

* Button 1: Add 1
* Button 2: Add 5
* Buttons 1+2 simultaneously: Add 10
* Button 3: Add 20
* Buttons 1+2+3 simultaneously: Confirm

Solution #4:

* Button 1: Increase amount by 1
* Button 2: Cancel
* Button 3: Confirm

Of course each approach requires different sub-solutions (as mentioned above, timeouts, detection of long presses and button holds, simultanous presses, etc.). These are up to you, but if you get stuck, feel free to ask :)
> 5 votes

# Answer
## Use a Motor as Input

You may be limited by the amount of *touch* sensors you can use, but you have one very useful form of input that you may not be aware of.

EV3 motors have the ability to provide a value based on rotation in degrees. Adjusting the rotation of the motor by hand, you can input very precise numbers quickly. To rotate the motor easily, attach any Technic wheel/gear to the motor using an axle.

---

## Programming a Basic Dial Input

Create a *unlimited loop block*, this will ensure the current rotation value is always updated. Place a *rotation sensor block*, set to measure in degrees.

The rotation sensor is very sensitive, it's almost too sensitive because it makes it very difficult to select a number without jumping to another. I recommend you divide the output from the previous block by any number between 10 to 70 to decrease the sensitivity. (10 being the most sensitive).

The divided numbers are now non-integers, we don't want to be able to take out a fraction of a dollar/pound or whatever currency you are using.

Use the *round block* to round the divided numbers up to a whole number.

**Optional:** Add a currency prefix. You can use the text block to add a currency prefix, in this case I used the $ sign. EV3 only excepts the $ currency in text inputs. If you would like to use a different currency you would have to render it as an image.

Display the current amount selected using the display block.

**Program Overview**

---

## Working Example
> 4 votes

---
Tags: ev3, programming
---


title: Trying to ID a piece.

text:
# Question
Title: Trying to ID a piece.
Light grey, approx. 1 in. X 1 in. Shaped like a bottom jaw or a digger shovel. It has a half round hump in the middle of the piece.

# Answer
> 6 votes
Pretty sure you're describing a Bionicle Krana Holder 3 x 4, which allegedly comes in light grey, dark grey, brown, red, blue, and green.

---
Tags: part-identification
---


# Question
Title: What parts are include with this light blue bike?
I need to find the part numbers of parts on this bike.

# Answer
> 6 votes

---
Tags: piece-information
---


title: EV3 with NiMH batteries

text:
# Question
Title: EV3 with NiMH batteries
Could I use 6 NiMH 1.2V batteries and keep pressed the small black circle in the battery compartment in order to adjust the battery gauge and low battery alarm?

# Answer
EDIT:

Yes, pressing the button will affect the indicator and low battery alarm/shutdown.

From the official LEGO firmware:

```
#define   BATT_INDICATOR_HIGH           7500          //!< Battery indicator high [mV]
#define   BATT_INDICATOR_LOW            6200          //!< Battery indicator low [mV]

#define   ACCU_INDICATOR_HIGH           7500          //!< Rechargeable battery indicator high [mV]
#define   ACCU_INDICATOR_LOW            7100          //!< Rechargeable battery indicator low [mV]

...

#define   LOW_VOLTAGE_SHUTDOWN_TIME     10000         //!< Time from shutdown lower limit to shutdown [mS]

#define   BATT_WARNING_HIGH             6.2           //!< Battery voltage warning upper limit [V]
#define   BATT_WARNING_LOW              5.5           //!< Battery voltage warning lower limit [V]
#define   BATT_SHUTDOWN_HIGH            5.5           //!< Battery voltage shutdown upper limit [V]
#define   BATT_SHUTDOWN_LOW             4.5           //!< Battery voltage shutdown lower limit [V]

#define   ACCU_WARNING_HIGH             7.1           //!< Rechargeable battery voltage warning upper limit [V]
#define   ACCU_WARNING_LOW              6.5           //!< Rechargeable battery voltage warning lower limit [V]
#define   ACCU_SHUTDOWN_HIGH            6.5           //!< Rechargeable battery voltage shutdown upper limit [V]
#define   ACCU_SHUTDOWN_LOW             6.0           //!< Rechargeable battery voltage shutdown lower limit [V]

```

The `BATT_*` are used when the button is not pressed and the the `ACCU_*` values are used when the button is pressed.

ORIGINAL ANSWER:

The small black circle is used by the Li-ion battery pack from LEGO. This battery pack actually operates at a higher voltage that Alkaline batteries. On the other hand, NiMH batteries operate at a lower voltage than Alkaline, so pressing the small black circle would have the opposite effect of what you are hoping that it will do.
> 1 votes

---
Tags: ev3, battery
---


# Question
Title: EV3 SPIK3R on Mission 5 just keeps backing up
I completely built the Mindstorms EV3 Spik3r. Missions 1-4 worked fine. However, with mission 5, and using the pre-made program, the robot just keeps backing up, instead of facing the bug, shooting it and then moving towards it. I put the 'bug' right in front (5cm) of the robot, and it backs up. I put the bug a bit further (50cm) in front, and the robot still keeps backing up.

If I hold the bug in my hand and move it to about 5 cm from the sensor, above it (like a 45-degree angle), then the sensor detects the bug, and the robot shoots at it and then tries to crush it. But it seems pretty flaky.

Is there an EV3 program I could download to help me debug this, or at least understand what's going on? Perhaps a program that shows the ultrasonic sensor's reading in real-time on the brick so I can move the bug around and see what the readings are?

What else could I try?

# Answer
> 1 votes
> Perhaps a program that shows the ultrasonic sensor's reading in real time on the brick so I can move the bug around and see what the readings are?

You can easily view the ultrasonic sensors readings in real time. To do so, turn on your EV3 brick, navigate to the 'Brick Apps' tab (second from the right) and launch the 'Port View' application.

Use the EV3 buttons to find the port which your ultrasonic sensor is connected to. The ultrasonic sensor value should be shown.

---
Tags: ev3
---


# Question
Title: How good are used lego bricks on bricklink?
In my life I've only ever used new Lego bricks; however, I'm now interested in purchasing large quantities of bricks and Bricklink's used section has significantly cheaper prices. I know that the quality of used bricks would vary by seller, but on average how good are they?

If they come from a smoking household can you actually smell the smoke? Is it really even possible for bricks to break or chip? Would it be obvious if I combined used and new bricks together in the same model?

# Answer
> 4 votes
I would suggest that you check with the sellers, as well as their feedback. There is a huge variety and quality of used bricks sold. For some sellers you can't tell used from new at all. Other sellers mention in detail the condition of used pieces; dull color, small chips and scratches, discoloration - most of these are fully functional elements and are perfectly good for general building and play, but might look a bit noticeable when you mix them with shinier new pieces. Then there are sellers who simply separate new from used, and don't mention the condition of used pieces at all. You could get anything from minor scratches to bite-marks and broken pieces. (Yes, LEGO pieces can break.)

In general, for used elements the acceptable standard is that they are fully functional but they may have some small chips, scratches, etc. that will happen with normal handling and play. Broken pieces, bite-marks, cracks, etc. must be mentioned, although some sellers don't. Also, the fact that sellers deal with tens of thousands of tiny pieces, it is quite possible that even an honest and good seller will have some subpar elements mixed in their used lots.

I would also like to point out that there are buyers who are looking for damaged and discolored pieces. They use them to add variety and interesting detail for such things as post-apocalyptic or battle dioramas. So yes, even heavily used parts sell well, and sellers listing them are not necessarily dishonest or bad - as long as they mention the condition.

Personally I only buy used pieces when it is from a seller I dealt with before and I know their standards. Or when a piece is rare and no longer available in new condition, or would be very expensive new. And I would never buy used white pieces as those are notorious for discoloration. Also, I would suggest that you do not buy from smokers. Smoke definitely penetrates plastic and it is pretty much impossible to get rid of.

Again, the best thing to do is to contact the seller ahead of time and ask them what is their standard for used pieces. Keep a list of sellers (you can favorite them and make notes on them) who you have a good experience with, and avoid the ones who send you pieces you are not happy with. You can also ask on the BrickLink forum for people to suggest you sellers who have decent quality control for used pieces.

---
Tags: shopping, bricklink
---


# Question
Title: Large blue windscreen with shuttle decal
Can someone help me identify this part, I got it in a bulk lot and want to know what sets are in there.

# Answer
> 4 votes
This is a Windscreen 8 x 6 x 3 Wedge with Space Port Pattern on Top and Sides (Stickers) - Set 6453.

---
Tags: part-identification, set-identification
---


# Question
Title: No response when controlling the Mindstorms EV3 brick over Bluetooth
I am trying to control the EV3 using direct commands over a Bluetooth connection. There are no issues pairing the brick with a PC or phone, and opening the serial connection works fine, but sending a direct command such as playing a tone with

```
0x06 0x00 0x00 0x03 0x0B 0x02 0xF4 0x01

```

does not produce a tone and does not provide a response on the serial connection, even though the telegram type byte requests it.

I have tested direct commands using two different serial terminals on OS X and Windows 7, as well as an Android app made for this purpose and writing the bytes using my own custom program, and all of these give me the same results. However, the official Robot Commander app does work.

Are there any special connection settings needed for commands to succeed, or any common pitfalls that I might have fallen into? I have read the developer documentation and didn't find any glaring problems.

# Answer
> 0 votes
Using the documentation from here, here, here and here, the command for playing a tone should look something like this:

```
0x0F, 0x00,            // size of message = 14 bytes
0x00, 0x00,            // message counter = 0 [can by any number]
0x80,                  // command = DIRECT_COMMAND_NO_REPLY
0x00, 0x00,            // 0 bytes for global variables, 0 bytes for local variables
0x94,                  // opSOUND
0x01,                  // CMD = TONE
0x81, 0x32,            // VOLUME = LC1(50) [50%]
0x82, 0x0B, 0x02       // FREQUENCY = LC2(523) [C5]
0x82, 0xF4, 0x01,      // DURATION = LC2(500) [0.5s]

```

---
Tags: mindstorms, nxt, ev3, bluetooth
---


# Question
Title: Tufts MAZE LabView Program Will Not Run on EV3
Through the 2012 LabVIEW for LEGO software package, I found an example of a maze from Tufts. I cannot get it to run on an EV3. It appears to just constantly execute the initialization.

How can I attach the vi to a question?

# Answer
> 1 votes
LEGO MINDSTORMS EV3 was not releases until 2013, so I think it is safe to say that the software in question was designed for the NXT only and will not run on the EV3.

---
Tags: ev3, programming
---


# Question
Title: Any issues with this non-standard gear combination of 12t gears?
I don't see any "accepted" gear ratios for a stud-less direct-diagonal gear combination on sariel's excellent gear coupler

but by shifting 12t gears such that they mesh off-center, it seems to work (i.e. spin correctly)

Any potential issues with this? will they wear down faster? will they not deliver as much torque as normal? is it less efficient than other combinations for those positions?

# Answer
> 1 votes
In your setup, the space between both axles is about 11.31mm (1 stud brick = 8mm).

On the central part of the gear (the band where teeth protude), the pitch diameter is 11.9mm (outer diameter of 13.8mm, root diameter of 10mm). Hence the gears would not mesh if mounted in the same plane (because 11.9 \> 11.31).

However, if you consider the beveled part of the gear to be like a smaller spur gear, its outer diameter is about 12mm (possibly smaller) and the root diameter is at most 8mm (more likely 7.9mm). The gears mesh because (12+10)/2 \< 11.31 and (13.8+8)/2 \< 11.31.

You can check the measures with a caliper.

What might be a problem is that in this setup, gears will be forced to rotate at the same speed while having different pitch diameters depending on the part of the gear, so the gears are likely to wear down faster. Now, the bevel gears are made of a softer plastic which whistands deformations better than other gears so it might just do.

---
Tags: building, technic, design, gears
---


# Question
Title: Mindstorms EV3 3D building instructions no longer working in Chrome
Lego Mindstorms EV3 building instructions in 3D (so that one can rotate the model around and stuff) are available. This used to work fine on my machine in Google Chrome. However, I can no longer get it to work; when I click on any of the links, it says "Looks like our 3D view does not work in your browser. Try to use a different browser or download the PDF instead.". I followed instructions to make sure webgl is enabled in my browser, and I also verified that webgl indeed does work. What do I need to do to get the Lego Mindstorms EV3 building instructions in 3D to work in Chrome (version 45.0.2454.85 m)?

# Answer
Google deprecated support for NPAPI in April this year, and removed it completely this month in Chrome 45.

LEGO has historically used Unity Web Player for a number of their online 3D games which has certainly been impacted by this change, and while this is not specifically the case here (the building instructions are "Powered by Autodesk Technology", possibly a variant of A360), it's probable that the underlying cause is the same - the plugin uses the older technology that Google is removing.

They do still work in Firefox if that helps.
> 3 votes

---
Tags: ev3, instructions
---


# Question
Title: Need help identifying this star wars set
Need help identifying this old star wars set, trying to rebuild my LEGO sets!

# Answer
The parts are from the 8016 LEGO Star Wars Hyena Droid Bomber from 2009.
> 9 votes

---
Tags: star-wars, set-identification
---


title: Gibberish Sound Effect

text:
# Question
Title: Gibberish Sound Effect
I am now creating my first LEGO stop motion animation with sound effects.

I do not want to use a specific language for them speaking. Instead, I am using subtitles. For the talking sound effect, I would like to use the gibberish sound effect that is used in some LEGO-sponsored video games.

I have looked around the web for hours now trying to find this sound effect and, sadly, cannot find it anywhere. Does anybody know where I can find this sound effect?

Does anybody know how I can maybe recreate it?

# Answer
There is no one gibberish sound effect for LEGO minifigures.

Traveler's Tales (the developer of many popular LEGO video games) creates its cutscenes with a mime/sound effect style similar to movies found on the LEGO website. Rather than record character voices with words (as Warner Brothers did with *The LEGO Movie*) Traveler's Tales recorded voice actors to mimic gibberish murmuring, grunting, and other non-lexical sounds.

If you would like to emulate this filmmaking style, I suggest you use a microphone of your own and record the sounds yourself. Have fun!
> 4 votes

# Answer
You could try looking for speaking sound recordings on free sound effect websites, like this one. You might use foreign languages too, those have an additional layer of realism over an indiscernible muttering, provide a nice easter egg if they really mean something (just make sure they aren't offensive :D)
> 0 votes

---
Tags: lego-games
---


# Question
Title: Overview of Engineering Principles incorporated in Technic LEGO sets
I run an after-school technology education program and want to expose kids to real-life engineering by means of having them build commercially available Technic kits which we then deconstruct and analyze.

I am looking at 42042 Crawler Crane's second model as a good example of how to build a strong vertical structure, plus it serves as a good example of how a weight & counterweight works.

I would have loved to use 9398 4x4 Crawler as it showcases differentials, steering principles, a servo motor as well as suspension, but unfortunately that model is no longer for sale (I'm not willing to pay the ~$300 some sellers ask on Amazon.com), so I think I'm settling for the smaller, non-motorized 42029 Customized Pick-up Truck.

I assume both models will give me plenty of gearing examples.

I am looking for your advice: What other engineering principles does Technic LEGO showcase, and which (ideally current) model(s) would you suggest I use to illustrate these?

# Answer
> 1 votes
This depends on how deep engineering principles do you wish to teach. For simpler, shallower things, like the inherent stability of a triangle based construction versus a square based, the crawler crane already offers a lot: the relation between force and leverage, skid steering, gearing, pulleys, gearboxes, electronics. Pneumatics and shock absorbers are missing from this set, but you can get some pneumatic parts from the 42008 Service truck.

For advanced concepts like Ackermann steering, Camber, caster and toe it would be hard to find official models to demonstrate, but you can always build simple models to display one or more of these features.

There are a few other things that I can think of, like fiber optics, but these are really hard to find nowadays.

Of course besides mechanical engineering there is also computer engineering, for which the Mindstorms sets offer an admittedly expensive introduction.

---
Tags: building, technic
---


title: What about these old houses?

text:
# Question
Title: What about these old houses?
I recently inherited two old Lego buildings. Unfortunately I have virtually no information about the history of them other that they been part of the inventory of an old hardware store closed a decade ago.

By the look of them I would guess they are from the early 70's. The windmill-house has some of the old red, blue and yellow Technic gears in them and a custom non-Lego motor to make it spin forever.

Everything is glued together but there is apparently parts broken off in some places.

Some theories:

* Are they custom built in the old hardware store without blueprints?
* Are they part of some Lego advertising campaign?
* Are they actual Lego sets with a number to reference them?

Does anyone know anything about them? Would they be worth some money?

# Answer
The top picture is for sure a model created from single elements, and is not any Lego model.

Your lower model looks like a combination from 5 or 6 different houses. I recognize the Taxi station (Red with blue roof on the bottom), Bakery (Yellow and blue roof on top of that).

Try brickset.com and look for the older catalogues.
> 3 votes

# Answer
To answer your three bullet points: Very likely. Possibly. Highly unlikely.

Sad that they are glued, but they are still pretty cool. You might get some money for them if you find a buyer.

Regardless, thanks for posting the pictures, I love the techniques for the big grey roof.
> 2 votes

---
Tags: set-identification, history
---


title: Need help identifying this set

text:
# Question
Title: Need help identifying this set
These came in a clear bag labeled with the number 2. Dated 2011.

# Answer
> 4 votes
Was it 10667 Construction? The date is a little off, but the parts look right.

# Answer
> 2 votes
As @Kramii already said, this is LEGO Juniors set 11067 Construction. Specifically the bag that makes the crane, without the Octogonal base plate (which was likely supplied separately in the box). Based on the picture Kramii posted you can see how to build this part of the set - you put the 6x6 black plate in the wrong place in your picture, it needs to be at the top.

---
Tags: set-identification, city
---


# Question
Title: I need help Identifing this set by the picture
I have a blurry picture of a set I found at a LEGO fair, and I would like to know what it is:

Thank you.

# Answer
That picture is quite blurry, but I'm pretty sure it's 8466 4x4 Off Roader from 2001:

The wheels in the picture look like they are metallic silver, and I think this is the only set of this size with metallic silver wheels and lime accents.
> 4 votes

---
Tags: technic
---


title: identifier expected?

text:
# Question
Title: identifier expected?
What identifier is expected here?

```
#import "rw.txt" rw

task main()
{
    if(rw != NULL)
    {
        OnRev(OUT_A,75);
        Wait(100);
    }
}

Error: # Error: Identifier expected

```

I don't seem to be able to find a API describing the NXC API very well..

# Answer
The error was caused because the file `rw.txt` was not uploaded to the nxt performing:

```
 t2n -v -put rw.txt

```

Solved the problem.
> 1 votes

---
Tags: nxt, nxc
---


title: fgetc() moves pointer one step forward

text:
# Question
Title: fgetc() moves pointer one step forward
I have opened a file using `handle = fopen("rw.txt").` The file consist of 3 values which is separated with spaces ex: `12 23 34` using `isspace(fgetc(handle))` Problem here is that `fgetc()` increments the internal pointer, making store incorrect strings including string.

Can these three values be stored in some different way, making me store these values, and ignore the whitespace using NXC syntax?

Here is my current code:

```
#import "value.txt" val
task main()
{
    byte handle;
    handle = fopen("value.txt", "r");
    if (handle != NULL)
        {
            string a;
            string b;
            string c;
            int count = 0;

           while(count <= 2)
           {
               if(!isspace(fgetc(handle)))
               {
                   if(count == 0)
                   {
                         fgets(a, 2, handle);
                         TextOut(0, LCD_LINE3, "done a" + a);
                         TextOut(0,LCD_LINE4," lenght: " + NumToStr(strlen(a)));
                         Wait(3000);
                         count = count + 1;
                         ClearScreen();
                   }
                   else if(count == 1)
                   {
                        fgets(b, 2, handle);
                        TextOut(0, LCD_LINE3, "done b" + b);
                        Wait(3000);
                        count = count + 1;
                        ClearScreen();
                   }
                   else if(count == 2)
                   {
                        fgets(c, 2, handle);
                        TextOut(0, LCD_LINE3, "done c" + c);
                        Wait(3000);
                        count = count + 1;
                        ClearScreen();
                   }
               }

                TextOut(0, LCD_LINE3, "done" + NumToStr(count));
               Wait(3000);
               ClearScreen();

            }

        }
    }

}

```

# Answer
> 4 votes
The most basic solution would be to store the character read by `fgetc`, for example, instead of:

```
if(!isspace(fgetc(handle)))

```

you'd write:

```
char val = fgetc(handle);
if(!isspace(val))

```

This way if the `isspace`call returns false you will still have the latest character in the `val` variable.

I'd also suggest you look into the `switch` statement instead of using multiple `if`-`else` blocks: http://bricxcc.sourceforge.net/nbc/nxcdoc/nxcapi/switch.html

---
Tags: nxt, nxc
---


title: "File error!" appears on NXT, but why?

text:
# Question
Title: "File error!" appears on NXT, but why?
I tried to upload this program to my NXT, but for some reason I am not able to run it properly as it is always terminated with the message `File error!`. No idea why.

I am trying to read a .txt file into a `char road[][]`. I think it is where I insert the value into my 2d array where things go wrong.

```
#import "road.txt"

task main()
{
    FileOpenType road_txt;
    file.Filename = "road.txt";
    SysFileOpenRead(road_txt);
    char road[][];
    while(road_txt.Result == NO_ERR)
    {
       for( int i = 0; i < 10; i++ )
       {

         for(int j = 0 ; j < 09 ; j++)
         {
            char temps = fgetc(road_txt.FileHandle);
            if(temps != '\n')
            {
                road[i][j] = temps;

            }
         }

       }

    }

}

```

# Answer
> 1 votes
Most probably the problem is that the array is declared, but not initialized. The program does not know how much memory to allocate for this specific array and therefore there is no available storage in RAM for it.

To solve this, try initializing your array. You can either provide the starting dimensions during declaration, like in the last example here. Which in your case would look like this:

```
char road[10][9];

```

And it will result in an array the given size, filled with zeroes.

Or use a function call to do the same if you have specific (not 0) initial values: http://bricxcc.sourceforge.net/nbc/nxcdoc/nxcapi/group\___array\_functions\_ga49d48de55d817e96ed132eadc21260eb.html

---
Tags: nxt, nxc
---


# Question
Title: What is the best way to get in contact with a Lego expert?
Catawiki is looking to hire a Lego expert to estimate the value of offered sets and arrange its weekly Lego auction. Where and how could we find people who might be interested in such a position?

# Answer
> 2 votes
An effective way of contacting LEGO hobbyist is either by..

* Contacting Local LEGO User Groups or similar hobbyist associations

Many countries and areas have their local associations. For a map of regional associations, see LEGO Ambassador Network's LUG map. By contacting representatives of association, you can easily contact local help.

* Requesting help from online LEGO forums

Another option is to post a message at online LEGO forums. There are many forums as some are theme-specific and some are area- or language-specific and thus it is hard to pinpoint exactly which forum one should try; it depends on the case. Safe bet would be to post in few of the global online forums, such as Eurobricks.

* Contacting individual hobbyist via site/blog/email

If one wishes to contact particular hobbyist, a good way is see if that particular hobbyist has own blog or similar page. Even gallery services such as Flickr often contain email which can be used to contact the hobbyist.

For this particular case, I would advice posting a message at Eurobricks since it has particularly large amount of readers.

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Tags: set-identification
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title: Identify age of parts from yard sale

text:
# Question
Title: Identify age of parts from yard sale
I purchased a box of LEGO bricks from a yard sale. Some of the 1x6 bricks are hollow with 2 small slants in them. Other 4x6 plates are very thin with square holes in the bottom. It also came with windows with half moon shaped holes in the bottom. Lastly white blocks with clear inserts in the bottom. Does anyone know how old these are?

# Answer
> 6 votes
**1 x 6 Bricks**

According to BrickLink, 1 x 6 bricks like the ones you describe were made between 1955 and 1969.

**4 x 6 Plates**

According to BrickLink, there were no 4 x 6 plates with square holes (so-called waffle-bottom plates.) There were, however, 4 x 8's made between 1954 and 1971.

**Windows**

Don't know...

**White Blocks with Clear Inserts**

The white blocks with clear inserts could be wheel holders, made between 1959 and 1992:

Or some kind of light brick:

It sounds as if your bricks are relatively old, probably made sometime in the 60s. If some of them look a little distorted and don't grip very well, they're probably made of Cellulose Acetate rather than ABS, which would fit with the dates.

To provide any degree of accuracy, however, we really need more information, preferably photos. Also, it might help to know what part of the world you're from, as back in the day there were sometimes different sets for different markets.

# Answer
> 2 votes
The white blocks with clear inserts (provided they have LEGO markings, a clear side window and 2 or 3 holes on the other side - I can't tell because you didn't post any pictures) could be 08010 Electric Light bricks, which were produced between 1980 and 1987.

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Tags: part-identification
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