I finished the coil winder a month or so ago and since I’ve used it a great deal. It was definitely worth the effort to build. It lets me make 1500 turn inductors in a matter of minutes. Coupled with Makespace’s Form1 to print coil formers, the results started to look pretty professional.
I ended up driving the stepper from an STM32 Nucleo F030. It is programmed so a push of the user tact switch will trigger an interrupt and the board will micro-step the motor for 100 revolutions. This gives a bit more control than just sending it off on the whole 1500 turns at once. Using the Nucleo board also meant I didn’t have to add a separate button, as I would have using an Arduino.
It’s been a long time since I wrote any updates about my IN-3 matrix project. Whilst I haven’t had much chance to work on it it has come a long long way from the original 4×4 tester.
I built an oak frame, machined an mdf board and attached 128 bulbs. Then I started the long process of wiring up each bulb to the PWM driver boards. In hindsight, I should have designed some kind of PCB strip to connect the bulbs to. This would have saved many hours of labour and been a lot neater. As it is each row of 16 bulbs takes about 1 hour to wire. Very boring so next time I know what to do!
I opted to buy a high(ish) voltage supply from eBay, the display can draw a lot of power when fully lit so despite having literally hundreds of high voltage driver boards for my IN-9 kit I figured to play it safe!
I am still only running some test code to make sure the bulbs light up and in the right order. I’m using an Arduino and the Adafruit Adafruit_PWMServoDriver library to communicate with the PCA9685 PWM drivers. Once I find a couple of hours to finish off the last two rows I’ll focus on what to use as a controller (probably the Teensy I’ve had laying about for 3 years) and actually write some proper firmware.
I’ve also now added a Github repo with all the hardware design files (DesignSpark PCB) for the driver boards and arduino sketches. I’ll continue to add to it as I progress.
For the last few years, I have repeatedly and frequently needed to wind a wire around a thing. From making RFID antenna to transformers. I switched job about 6 months ago and naively thought my winding days were over. However, I was wrong. By some freak accident, I’m back winding wire onto ferrite rods. This time though I need to make some whopping 1H inductors. I’m not going to sit here and wind a thousand turns by hand, not while I have a stepper motor, a microcontroller and a makespace next door.
After a couple of hours on Fusion360 I had a design and I was off to laser cut it. Doesn’t look too bad. The rest of the parts should arrive tomorrow when I can finish this beast.
It’s been a little while since the end of my latest Kickstarter, a kit to drive 2 IN-9 nixie tubes and it’s been a very busy time. However, after a few hurdles rewards are being shipped. To go along with the shipped rewards I have written a few example Arduino sketches and an assembly guide. These can be accessed from a new tab at the top. This will take you to a page covering how to assemble the kit and a link for the necessary Arduino sketches.
It was a pretty straightforward task to assemble the bits into a functioning 4×4 nixie matrix. The tubes are mounted on spray painted black MDF with the PWM driver mounted on the back. They are each held in place with a small square of double sided foam tape. Wires soldered on the back to the tubes create a small nest and will be more neatly managed of the bigger version. I programmed an Arduino with the Adafruit pwmtest example and it all works fine. In fact, it works much better than I expected and I think I’m ready to go full scale, with no real modifications. All seems too easy.
I did a measurement of power consumption and the 4×4 uses a power of 1.8W, so will need about 15W for going full scale. Not too bad really for 128 tubes.
Running a PWM test.
I recently bought a few (200) IN-3 nixie bulbs. Unlike the familiar numeric tubes or the bargraphs I’m fond of, these are just little bulbs. They have commonly been used as dots between digits in clocks and alike. Not content to make just another run of the mill Nixie project I decided to build a Nixie matrix, much like an LED matrix but with the lovely orange glow. My eventual aim is an 8×16 matrix, enough to display basic numbers and graphics. Though I’m starting with a simpler 4×4. This does provide the first challenge, how to drive so many tubes? The common way is multiplexing, however, since this is a one-off build and additional electronics isn’t too important (I’m not trying to optimise a BOM and a bit of extra work is fine) I have opted to directly drive each IN-3 tube. Not only drive each tube on and off but with a PWM signal. This should allow nice brightness variations and fading effects across the matrix. Pretty sexy. So now I just need 128 PWM channels… For ease I’ve gone for a 16 channel LED PWM driver (PCA9685). There’s even a nice Adafruit library for quick Arduino testing. It’s I2C so I intend the chain 8 of them together, these are driving mosfets that switch the high voltage tubes. (I’m also putting together an IN-9 driver kit (watch out Kickstarter…) so I have an abundance of high voltage supplies.)
So far I’ve fully soldered up 4 boards and tested one with 16 tubes. All working nicely. Today I’ve cut out a small 4×4 MDF board to make up a little test board to get everything right before I go full scale. So far, it’s all be smooth sailing. Wonder how long that’ll last.
Being Christmas I wanted to make something for the festive table. I also haven’t made a carving for myself in a while. I decided to make a tealight candle holder out of some discarded mahogany I had. The design is the superposition of 3 functions, each ripple out from a point, where the candle sits. The waves interfere with each other over the wood and reflect the candlelight. Looks pretty neat.