Audio Spectrum Visualizer IN-13, 7 Band.
Introduction: Audio Spectrum Visualizer IN-13, 7 Band.
Hello Guys,
This project was a long journey. I developed, tested and choose each part carefully. One step at the time, the whole project have forward slowly. But at the end. Wow it's an amazing product. Very proud of it. Lets begin.
Supplies
Part is available here Version 1.2
Almost all parts came from digikey.
In the part list you will find all part number needed.
Few other part came from ebay like IN-13 or tube acrylic holder.
This is not a cheap project. There are many parts and some are expensive. IN-13 are not in production anymore.
You will need to put some money and time in it. All is hand crafted except for pcbs. Tube are fragile and take a lot of care. At the end the result is unique and very beautiful.
Step 1: Specifications
Specifications I wanted:
* 7 Bands IN-13 tube.
* Hardware FFT
* RCA input
* Microphone input
* Low floor noise
* Auto On
* Auto Off
* Volume control as well
* Real Frequency Respond
* No negative power supply
* Integrated frequency generator to adjust each tube
* Invert mode. To put 2 spectrum side by side one mirror of the other.
* One PCB for everything, HVPS include.
* No add-on china module
Step 2: HVPS
Nixie in-13 are working at around 140 vdc. We will use a power adapter of 12v.
Let's making a HVPS for this.
The idea here is to short to GND a coil at high speed. This cause back EMF spikes of many many volts.
We add a diode to grab this spike and we accumule those spike in a capacitor.
A feedback (output voltage sample) is returning back to the controller and this one adjust the duty cycle (duration time) of the PWM (the coil shorted to GND). More the coil is shorted more the spike will be huge. But if the time is too long, the coil will just burn.
This idea is called a boost converter and many chip controller are available to do this.
On my nixie clock, i didn't have a controller. In fact, the uC was doing the PWM. The load is not moving so the PWM do not need to be change or adjust.
But with a graphic band visualizer, the load is constantly moving. In that case, we will use a step up (boost) controller.
Many could do the work.
UC3843B, available from texas instrument, ON semiconductor, STMicroelectronics. This is an old chip cheap and always in production. 552
Texas datasheet, ON datasheet, ST datasheet $0.58 usd
MAX1771, only available from Maxim Integrated. datasheet. Nick de Smith have already done a psu for this purpose here. Results are very good. $5.00 usd. See more details later why we can't use it.
Step 3: The Coil... Optional Basic Experience, Attention, High Voltage!
First, the choice of the coil. Must be around 2A with low resistance DC.
SDR1307-101KL is looking good. 1.9A, 0.180 ohm, 13 mm round, surface mount, good price.
B82479A1 also have nice specification for our needs.
I draw and try this schematic. This is just a test on prototype board. We can't have good efficiency this way. This is to demonstrate the principle of operation.
Frequency input will be TTL 5v from 20kHz to 70kHz 50% duty cycle
Step 4: Trying HVPS
I did 5 HVPS with different controllers, different pcb arrangement. The goal here was to find a good efficiency, low cost part with low noise.
I also tried Nick HVPS here
The author here did a very good job. And yes the efficiency is 85% I tested it. The max 1771 give a modulated frequency to drive the mosfet. The modulated frequency is lower than 20khz and this bring me a big problem. I was seeing it on the tube! Definitely not a good thing. I had no choice to draw something myself for my needs.
Finally I choosed the UC3843B and clock it to 36kHz. At this speed, this isn't transmitted on the tube, problem solved. I did 4 littles pcb to tried different configuration of component until, under test, was perfect.
1 tube take 71ma. 7 tubes full turn on takes 500ma for a total of 6w only. My power supply can go to 10 watts easily. 552