Neon Ring Counter Heart
Introduction: Neon Ring Counter Heart
Valentine's Day is always accompanied by a fierce swirling of emotions. I find myself light-headed, out of breath, and anxious counting down the days to February 14th. This time of year, I ask myself some of life's hard questions, questions like: "When will my parts arrive? What happened to my wire cutters? Who melted my soldering iron? Why is my table on fire?" Yes, because for many makers Valentine's Day is an annual, obligatory challenge to make a gift for someone. Although you'll definitely be more attached to your creation than they'll be, it's the thought that counts!
This flashing heart is unique for two reasons:
1. It uses neon glow lamps instead of LEDs.
2. It lights the bulbs sequentially without using any sort of digital circuitry. (Only the neon bulbs, resistors, capacitors, diodes, and 90V DC!)
I'm a big fan of neon bulbs, so I was excited to discover that they can do some things modern LEDs flat-out can't. This circuit is called a neon ring counter, and it uses the switching properties of neon bulbs to light one bulb at a time in a loop with any number of bulbs. 982
I modified the circuit slightly so I could use a neon bulb to generate the pulses that make the ring counter advance. (The center bulb flashes each time a new outer bulb lights, but because the flash is so brief the camera doesn't always catch it.) Inside the case there's an adjustable 5V to 90V converter powered by USB to drive the ring counter, so you can power the heart from a phone charger or probably a laptop.
One unusual part of this project is that you'll need to customize the circuit for every heart you make. The NE-2 neon glow lamps I chose don't have very precise striking and maintaining voltages, so to make a reliable ring counter it's necessary to age a batch of bulbs with AC and then select bulbs with similar electrical characteristics, as explained below. The resistors and input voltage for the ring counter depend on the striking and maintaining voltages of your bulbs, so I can't give you one-size-fits-all values, but I'll show you how to calculate them.
This project requires through-hole and SMD soldering, ordering two custom printed circuit boards, and 3D printing a case. In addition, it's necessary to breadboard and test the neon ring counter with your aged bulbs, since this circuit can take some tweaking to make it work well with common neon indicator lamps. The only danger with this project is aging the neon glow lamps, which involves connecting them through a resistor to the high-voltage AC wall power. Mains voltage is dangerous, and you should only attempt this project if you understand and acknowledge the risks.
Let's get to it!
Supplies
Tools:
* Soldering iron and solder
* SMD soldering equipment (solderpaste, hot plate or reflow oven, tweezers)
* 3D printer (I used a resin printer, an FDM printer could work though)
* Breadboard for prototyping
* Multimeter
* Wire cutters and wire strippers
* Glue (I used tacky glue, which is convenient because it turns clear when it dries)
Parts:
This project requires surface-mount resistors and capacitors. There are variety packs available online (like this one), which I would recommend if you want to get into surface-mount soldering.
Ring Counter Heart:
* Custom PCB
* NE-2 Neon Glow Lamps (like these)
* 17x assorted 0805 resistors (you'll need to pick resistances to match your bulbs, as described below)
* 7x 100nF 0805 capacitors
* 1x 0.1uF 100V ceramic capacitor (here, lower capacitance could work but needs to handle 100V)
* 1x 0.47uF 100V ceramic capacitor (here)
* 7x 1N4148 through-hole diodes
* Braided wire (to connect the heart to the power supply)
5V to 90V Adjustable USB Power Supply:
* Custom PCB
* 1x 10M 1206 resistor
* 1x 220 0805 resistor
* 1x 22k 0805 resistor
* 3x 0. 98