I've been in a distinctly sparky mood recently. I want to make a few eleccy things and just wondering what everyones thoughts and opinions are on all these ideas:
1) PC power supply - I'm converting an old PC power supply into a 12V, 6V and 3V power scource. No real modifications except shorting out a wire here and adding a connector there etc etc. Apparently it should be able to supply about 10A @ 12V. It's an old 250W supply (can't remember if it's xt, at or atx).
To create a stable output on the power supply, a small load is required, do you reckon the 2.2R 25W version of this resitor would be alright or would I need two and stick them in a pair to help with heat dissipation?
2) Voltage Monitor - if you have access to "everyday practial electronics" magazine, it's one of the projects in the July 06 issue. Basically monitors the 12V, 6V and 3V rails and displays via a simply LED bargraph whether the voltages are too high, high, ok, low or too low, with an alarm as well if any of them strays too far out of line.
3) Temperature - Again, if you have access to EPE magazine, it's one of the projects in the June 06 issue. It is a digital car display for fuel gages, oil pressure etc and converts an analogue signal into a digital signal, with a low or high alarm. I was thinking that I could put a thermistor in a small silicone sealed box/tube (like one of the glass test kit test tubes, siliconed at the top) and put that in the hang on filter. The surrounding water temp would heat the air inside the little box/test tube whatever and would eventually give an accurate water temp reading. I could then use the alarm setting to control a pair of 12V PC fans or a clip on fan via one of these relays:
If it works well I could possibly do the same again but use the alarm to control the heater through a min temp function and one of the relays linked above.
4) Auto top off - assuming PC power supplies can give the 10amps or so I've been told, presumably it'd be fine for the windscreen washer motor (they have a high current draw, anything between 3-5A I've been told)? If so, I'd build a small monostable that, when triggered by the floatswtich, would activate a relay to the pump for about a minute to prevent overflowing.
Any thoughts on all that? Sorry for ramble.