Project: SpinBalance – Introduction

I don’t have a good track record with mechanical projects – anything that moves. I do much better with purely electrical devices. As soon as you have moving parts you have to deal with things like friction, backlash, wear, tolerances, inductive spikes… I don’t like any of those things. Every couple of years I forget this and think it’ll be different this time, so here is another mechanical project.

A couple of years ago while still at university I started a balancing robot project. I quickly gave up. The reason was that my robot was free standing and balanced on two wheels. There were a number of issues:

  1. The robot would run around and I didn’t have enough space of my desk to allow it to balance
  2. The programming cable would restrain the robot so I also had to unplug my programming cable each time I wanted to test it – not ideal for quick iteration
  3. It was hard to control the environment and get the motors aligned
  4. The robot could not have an external power source so had to rely on batteries

This time I am still going for a balancing robot but I am going for a rotational robot, rather than a free standing robot.

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A “sketch” (Sketchy drawing)

Continue reading “Project: SpinBalance – Introduction”

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Project: MicroLit – PCB V1

This project ultimately just uses the power of the BBC Microbit to communicate via radio and control the LED strips, therefore this board started out purely as a passive breakout board to mount the MicroBit and connect it to the LED strip but quickly became more complex.

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Mini Project: Guitar Amplifier (old!)

Playing guitar and electronics have been two of my favourite things for a long time now. When I was about 14, I combined these two for the first time and built a pretty simply 32W amplifier. While the design is super simple, it actually has a really nice clean tone and does not distort the sound at all. It’s capable of diving an 8 ohm or 4 ohm load. Today I decided to give it a bit of a clean and check if it still worked.

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Project: Nixie Clock (upgrade) – SPI Bus Chip Select/GPIO Contention

As discussed in the previous article, the display is controlled by a number of shift registers. Shift registers can be controlled directly by a SPI bus, which is useful as most microcontrollers (including our ATtiny87) have a built in SPI bus peripheral. This means that writing a byte to the shift register is almost as easy as just writing a byte to a register.

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Project: Nixie Clock (upgrade) – Using 74HC595 Shift Registers

My Nixie tubes have 11 active pins each: a common anode and one cathode per digit (ten in total). The anode is connected to +180V via a 47k current-limiting resistor and each cathode is connected to the collector of a high voltage bipolar transistor (MPSA42) so that current can be controlled through each of them via the base of the transistor. This gives a total of 29 transistors that need to be individually controlled (24 hour clock requires 3 possible numbers for the first digit, 10 for the second, 6 for the third and 10 for the fourth). I chose to do this by using four 8-bit shift registers, connected in series to make one, 32-bit shift register.

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Project: Nixie Clock (upgrade) – Final Schematic and PCB

One big change since I did the first version of the clock is my access to professionally made PCBs. At the time, I was only able to produce PCBs via hand etching or using my home-made PCB mill. A board like this requires at least a double sided design which is not easy using the above methods and so I used veroboard. This is painfully slow and messy.

 

For the new version I will use a professionally made two layer PCB.

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