Been a while since my last post; been busy stressing myself over school and trying to actually relax a little with my Winter break. Fall 2010 went well in the end; I was quite worried about two of my classes going into the last few weeks, but I pulled everything around and somehow made a decent finish with three B’s and an A. X-Mas was good, even managed to get a Wii! Of course, I spent the last few days working on getting it soft-modded (fairly easy process at this point in the maturity of the product; relies on some crappy programming in a Lego Indiana Jones game that someone managed to exploit with a modified save file). I slapped together a 2.5″ SATA HDD and an external enclosure that runs it off of USB power, and now I have all the games I want! Thank you, Internets! Now Kim and I just need to find people to come over and play with us! >.<
As I mentioned a few months ago, I built a simple power supply into my synthesizer. I also finished putting in all the components on the front panel, which looks nice and spiffy; the rectangles of leftover acrylic that I glued to the edges to hold the panel to the case are still rather hackish (and always will be, because I didn’t give that mechanism any thought when I designed this thing!), but overall, I still think it came out just as well as I had intended it to over 4 years ago. Here is the overview of the internals of the power supply, which was pretty much ripped straight from the MFOS Adjustable 1.5A Bipolar Power Supply, but still required a good bit of my engineering construction know-how:
The placement of the components had to be very carefully scoped out in order to prevent any possible problems with interaction with the electronics above (both physical and electromagnetic) – while this overall project is pretty much mid-fi, I have been trying to spend at least a bit of my time on paying attention to hi-fi aspects like noise reduction and high-quality components. Of course, most of the wiring shown here is done with scraps that I needed an excuse to get rid of anyway, hence all the splicing (although even a lot of that is equally due to needing to move the transformers around after having put what I thought to be “just enough” wire length to keep things neat):
The larger transformer (which is pretty much the only product I actually WANT to buy from Radio Shack) is what is driving the regulator circuitry. I realized that a fan would be nice to have to cool those heatsinks, but discovered that the fan was making a mess of my power rails (even after putting in a huge bypass capacitor), so I took apart a wall-wart and ran it in parallel with the main power transformer to power the fan by itself (I know it is overkill, but it works and people pretty much give these things away!). I made the heatsinks with a good bit of hacksaw work on an old winged heatsink I had in my collection of dumpster-diving goodies from back in High School:
My oscilloscope shows this to be a very clean supply with excellent regulation; I did quite a bit of experimentation to make sure of this because, well, I could. It was fun! :D
On the outside of the case, I had a little geometry fun and hand-drilled about a hundred holes in a pattern for the fan intake:
It is a little noisy (acoustically-speaking, while using the machine), so I think I’m actually going to build a small regulator for the fan and place some thermistors to sense the temperature of the heatsinks and only turn on the fan when they actually need it on. However, it might be better to simply put in a lower-voltage wall-wart supply – the airflow is also good for the rest of the electronics inside.