Electronics PCB Manufacture Power Supply

So about 3 months ago, maybe more, I started looking into designing a modular synthesiser. I started off building a simple VCO, and ran into problems straight away with that, which needed a solid power supply with multiple rails. So I looked into building one. It didnt take long for me to design one, based around the LM317 and LM337 linear regulators, however this has really been put on a back burner with life and several other projects getting in the way (including moving the hackspace to a new premises!), but today I knuckled down and made the PCB in the garage.

power supply pcb
the final pcb, pre drilling

Now my workflow for PCB’s does need a bit more work, and the actual equipment does too… This one was done with the toner transfer method as it previously failed with the UV exposure method. It actually failed with toner transfer as well once, but using a clothes iron instead of a Laminator made the difference. I need to upgrade my ‘etch tank’ to something more than a glass baking dish and a tray heater, to a bubble tank. Heating is optional, it just speeds up the process. Will also be looking into the Edinburgh Etch method as well, which uses Citric Acid to improve results.

Anyway, back to the power supply. With the PCB made, I can finish off mounting everything into the case I bought for it – a plastic 19″ rackmount case. May seem a bit overkill, especially as this is only rated at 1Amp per rail, however I am trying this case out for other projects as well, and seems to be quite a good choice.

The case, buried under a few other boxes of projects

Here you can see the main power switch, 5 output rails, and possibly the green LED in the middle. The transformers are already mounted inside the case to a large sheet of aluminium, and just need all the connectors putting in. I will post more pictures of this when I finish the project off, and also go into upgrades I hope to do, such as microcontroller control, current limiting, and a more powerful output. For now though, need to wait until tomorrow to finish this off…

Electronics PCB Manufacture

UV Light Box Controller – Part 4

So, that took longer than I thought it would…

Once I put the whole thing together, with the controller board and power board, it didnt work – the Darlington wouldnt switch the power for the UV Array. Some peculiarity of the ones I have, or just the fact that it wont work like that… Either way, I had to go back and re-do that board. Oh and also replace the Atmega 328 – they dont like near on 18 volts into a control pin it turns out! So now I have a completely re-done power control board, with a Darlington, which is in turn switching a relay, which switches the UV Array. Phew! Also I fitted a lump of metal to the 5v regulator, although will need to find a better heatsink soon as its still getting rather warm…

Controller Board

So the controller board itself hasnt changed much, apart from a new atmega chip. Also its now fixed to the front of the UV light box!

Power Board

This is the part that has changed the most, what with the Darlington not working as intended. As you can see, the voltage regulator on the left now has a hefty bit of metal for a heatsink, but needs something bigger. The blue box is a relay from my dads bits box, wouldnt have thought it was powerful enough, looking at it, however it does the job rather well.

The UV Array

And in this last picture, you can see the UV array inside the box. Not much to see here, all the resistors are on the underside of the board, but you can see my amazing wire organisation! Yes the whole box is made of cardboard and gaffa tape, but it works. Eventually I will build something better, maybe even have more LED’s in the array… However for now this will do me nicely.

Now all this is finished though, I can go on to actually making more boards! Woo!! I will eventually sort out some schematics and board layouts for this, however most of the circuit I just made up from previous experience, so that may take a while!

Electronics PCB Manufacture

UV Light Box Controller – Part 3

So after a little bit of tinkering with the code, changing round the pin assignments mainly, I  built up a permanent version of the board in veroboard/stripboard/whatever you want to call it. And this is what we have!

The finished controller board

The left hand board has all the controller, lights, and buttons on it, and the right hand board has the Darlington Transistors, and a 78M05 linear regulator to power the micro. This now just needs connecting to the power socket on the box, and the UV array, and we’re done! Will post an update when its sorted.

Electronics PCB Manufacture

UV Light Box Controller – Part 2

Now, this is why i love the state of electronics at the moment – especially hobby grade ones. I can go from an idea on a piece of paper, to a working prototype, in… about 3 hours? Something like that. Anyway, in the time its taken since the last post, I have built and coded my Light Box controller, or at least prototyped it on a breadboard.

Isn't it pretty? 😀

The breadboarding was actually the easy part – as you can see there are 5 buttons, 9 LED’s, a big Darlington Transistor, and an Arduino (and battery, but thats just for portable power). The buttons, from left to right are: Reset, Pause, Go, Up, and Down, and the LED’s are (again from left to right): Power, Go, 8 minutes, 4 minutes, 2 minutes, 1 minute, 30 seconds, and Array. The array LED is just as a place holder until I actually hook this up to the UV Array I have built (more on that in another post).

So when this is running, the timer counts down (in binary) in 30 second intervals. You can set it to the nearest 30 seconds using the up and down buttons – up to 15 minutes 30 seconds, and down to 30 seconds. The reset button sets it back to 8 minutes, although only when it is paused. The timer can be paused, and will turn off the UV Array when doing so, which would allow you to move or adjust something in the box. This will also allow for the simple addition of a switch to detect if the door is open, although in my current box that is pointless… the door never actually shuts.

The code for this is below (click the read more link to see it!)

Electronics PCB Manufacture

UV Light Box Controller – Part 1

So setting out to improve my home PCB manufacturing, I am going to build a timer controller for my UV light box – using an Arduino and a few LED’s. nothing overly complex, apart from a Darlington Transistor for controlling the UV array.

The plan...

So after laying down the plan, its on to breadboarding and writing the code…. Stay tuned….


Electronics PCB Manufacture

PCB Manufacture – Part 2

So after a bit of experimentation, turns out its less the strength of the sodium hydroxide that matters, more the temperature. Using a water bath at ‘slightly warm’ (technical term :P) with a 1.5% solution, the board developed perfectly. This is after 8 minutes in the exposure box, but still, thats a 10mil trace its done. I think its 10mil anyway, will check my original drawing later. Just about to etch it to make sure its worked well.

exposed board ready for etching