General > General Technical Chat
Show your favorite and most used benchtop PSU
kallek:
Those Oltronix power supplies look really nice.
I just built dual rail power supply, but still my favourite and most used supply is very basic LM317 voltage supply with ten turn pot.
For AC I built variable isolation transformer with meters. When there was still some space left, I installed also dim bulb tester with bypass swith to same enclosure.
BravoV:
kallek, really nice, especially the AC adjustable PSU. :-+
I have isolation transformer and a variac gathering dust, I guess this will be my next project. :P
Btw, that dim bulb tester with by pass switch is on the output's side right ?
Also regarding the wirings, from the AC mains, is it connected to the transformer and then the variac for the out put, or the other way around variac 1st, and then transformer for the out put ?
kallek:
Thank you BravoV! I think it was cool project. I have used mine for testing new builds and also for 120V devices. And hopefully in future for powering restored vintage devices. :D
Dim bulbs are at first from mains. If you look carefully you can see bulbs glowing from transformers idle power. ;)
Variac is before transformer, because it is rated for higher current than transformer.
engrguy42:
Okay, well it's not my favorite...nor is it my most used...
And, honestly, I don't want to brag, but...
>>> INSERT TIM ALLEN/HOME IMPROVEMENT GRUNTS HERE <<<<<
As Nigel Tufnel so eloquently stated in Spinal Tap, this thing goes up to 11.
My modification to a 460 watt ATX power supply. And yeah, that's right, it's running just under 20 amps on the 12v output.
>>> MORE TIM ALLEN GRUNTS <<<<
BTW, not sure if you're all aware, but the International Institute for Determination of Ultimate Coolness (IIDUC) recently issued the following statement :
"The truly cool people use converted ATX power supplies".
So, for all of you "I hate ATX" fanboys, there you have it...
Now, to dispel a related myth:
If you run a big 'ol 4 inch diameter, 200 watt, 5 ohm rheostat at just over 200 watts for 30 seconds or so, it will NOT necessarily set off your smoke detector. Yeah, it might smoke a lot, but if you have a portable fan standing near your workbench and run over and turn it on quick enough, no problem.
jaycee:
Not the first PSU I've built, but the first one that was more than an LM317, and built into a proper box :)
It's a fairly common topology.. A TL082 as sense amps, and another as error amps. Voltage reference is a TL431. Transformer is custom wound but an off the shelf 2x9V (plus another small 2x9V for the opamp supplies) would work. The metering is done using an Atmel ATMega324, which also controls switching the load on and off via an illuminated pushbutton
I made a few little mistakes, the metering is not very accurate at the low range because the ADC in the ATMega is not very accurate near ground. I should have added some bias to the sense amps so that the voltages they output doesn't go near ground - this doesnt bother the opamps because they have a -ve rail
edit: Oh yeah, the important bits. It's 0-18V at 0-1A, and 90% of the components are recycled parts - including the ATMega324!
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