So I got the inductors in the post today, and had to work out how to fit all the boost circuitry into as little space as possible. I decided to make a little cylinder of parts, and heatshrink the lot, then I could cram it next to the multiplexing layer on the pcb. It was pretty easy to make, and I’ll be making a few more of these for various uses. The four wires are 5V, 0V, switching signal, and high voltage output. I’m using open loop control, and I get a stable 50V output – it’s weird that you can feel a tingle if you touch it, and it’s only powered by usb. The parts used were:
Mosfet – CSD18532KCS, but practically any will do if they can handle 60V and can be driven from a logic level.
1 high voltage capacitor – I used a 300uF 300V capacitor, you need one >60V and >50uF.
1 low voltage capacitor – I used a 220uF 16V capacitor
diode – I just used a random IN4001 one I had lying around
The circuit is the same as the ice tube clock (http://www.ladyada.net/make/icetube/design.html)
So here is what I have so far (you can just about see the end of the high voltage capacitor in the background. It’s powered only by usb, and displays 18:11:11 at all times. Now I just need to add the ds1307 when it arrives and write a little code.