Let's Make Robots!

The perfect power supply

hi peeps - im back

ok im looking to create the perfect desktop power supply with as many handy bits as possible and i'm looking for a bit of advice and inspiration from you lot. Ive done my research and have a pretty good idea of the direction im taking but lets be honest - the more the merrier.


as per usual i'll be taking the modular approach - each portion being a learning experiance in itself


1) linking anything to the mains still terrifies me so im probably going to use a leftover laptop supply i have

(input AC 100-240v , 1.6A , 50-60Hz)

(output DC 18.5v , 3.5A)


2) it will have one fixed 5v, one fixed 12v and a variable output


3) it will have a 3x7 segment digital display and push button control of the variable output


4) the front connectors will be both bannana input and wire grip versions 



5) i am also considering a second section powered from the same source as a potential reader (eg occiloscope or multimeter or lcd display kind of thing ) but one step at a time eh?




im essentially looking for advice on the various sections and how best to get them to interact without interfering with each other (eg the digital output lowering the actual output kinda thing)

thanks peeps



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I would use a more powerful voltage regulator, 1A is a bit weak. I would use some strong switch mode regulators.

This one is adjustable 2-37v w/ 3A, which is probably enough if you're not building Fanucs.

The 350K is the same regulator in a TO3 package.  The TO3 has MUCH better power handling capabilities, which you will need with that input voltage and an adjustable output.

what ampage would you guys recommend for the kind of electronics used in robotics?

From the various PSU mods I have seen this is the one I like best: http://tgbuilds.wordpress.com/projects/diy-bench-supply/
Variable voltage output and working leds on all the power lines plus current and volt meters.


thats definitly the style i was looking for - and the whole ATX (computer) theory is expanded that little further - thanks

I've used a couple of "old" computer power supplies as desktop supplies.

Since I'm usually after either 5 or 12 volts I've not bothered to set up a variable output.

I've not had problems with them.

As I remember it there are hits on Google re modifying for variable.

im seeing a pattern here

I think there might be something to be said for a lesson learned from "over-engineering" here though, too. The display aspect, while cool, could probably be more easily and less problematically managed with an analog solution-say a 317t (do they still make those?) with a potentiometer for the adjustment. In any case, it's the approach I'll probably take, but the idea of using a laptop or desktop power supply hadn't occurred to me. My design was to include a USB-A port to the dedicated 5v, a dedicated 9v with a retractable cable and fixed battery attachment, and the aforementioned variable analog out on bananas and another retractable line with DuPont connectors on the end. I kind of want it to fit under the scope/analyzer, so laptop might be the way to go. Hopefully that won't cause problems for the HP... I'm just getting tired of scrambling through the rats nest looking for the right wall-wart or line lump and then digging out the extension cord from under the tool pile and hoping nothing that could cause a short slipped into the socket.

We should all approach this from intentionally different angles and compare notes after the build!

they still sell 317t's but i'll be honest i'd rather have push button control and digital output than a turnable knob as it would teach me more about chip compatibility which i could use later - and as you mention it would look cool too.

the USB-A output in parralel to the 5v bananna's was something i was considering myself as its becoming such a common recharge / power source.

DuPont connectors and the 9v battery clamp are an interesting idea - a possibly better version might be to make the USB-A linked to the variable output which in turn goes to a multiple output box (via a cable) - you know like those you get for memory cards but in this case for outputs of our choosing.