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My school uses HY 3005D-3 but I want to do it myself to save on $. Before opening it, I ask for tips about: not-to-break-it, cheap DC supply and DIY-materials (not that I know them soon). So how to build, to get cheap DC Power supply with such adjusting knobs?

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Do us a favor and fill out your profile. Specifically change your username to something other then the default for Google openid users. – Kellenjb Jun 5 '10 at 23:20
Then maybe accepting some answers? – Johan Jan 12 '11 at 17:24

4 Answers

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Before I got a real powersupply I used different kind of AC/DC or AC/AC power adapters, the kind that ship with toys, mobile phones, routers etc etc...

Then I just cut the cord and measured the voltage with a multimeter, and if needed added a simple linear regulator like the 7805 (if I wanted a clean 5V).

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Apparently, 7805CWs are not explosive. Got it dirty hot even with 6A and about 5V. Just connected the outermost legs to catode and anode in the DC power-supply. Where do I need the middle leg? – hhh Jun 6 '10 at 13:54
... time to finish my explosion chamber :) – hhh Jun 6 '10 at 13:54
6A = Big heatsink... or spread the load over more than one power supply? – Johan Jun 6 '10 at 17:43
Is 7805CW a type of 7805? I wasn't able to find anything on the CW on google. I find it hard to believe that you are getting 6A and 5V. First of all, the middle lead on 7805s is a ground lead. I wouldn't think you would get much output without connecting this lead. Also, most 7805's that I have worked with start to drop their voltage after going over 1-1.5amps. – Kellenjb Jun 7 '10 at 1:02
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Personally I usually don't use 7805 (and the others) for bigger loads than 0.5A. But if you have a small design like a mcu that just needs 5V to run... – Johan Jun 7 '10 at 6:09
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up vote 5 down vote

Why not get one of these kits: http://bit.ly/ankadN and use with an old computer power supply? Then spend some time learning about power supply design, linear regulators, smoothing and so on.

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That looks pretty cool. However, as a warning to the person who asked the question, computer power supplies are great at pumping out a lot of current, but not so great at being low noise. You will learn have to learn fast how to reduce noise on your power lines. – Kellenjb Jun 6 '10 at 2:27
Yes, absolutely. Hopefully the OP is productively studying and not just trying to 'explode' components :) – tronixstuff Jun 6 '10 at 3:30
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+1 for suggesting reuse :) – hhh Jun 9 '10 at 4:53
There's also an Instructable on DIY'ing this. You have to be competent enough to open the PS and fiddle with the insides, of course. 115VAC and big capacitors. – John Lopez Jan 29 '11 at 17:11
up vote 4 down vote

Are you wanting a DC power supply for one specific purpose, or want a generic power supply that will do everything that the one you mention does?

You can fairly cheaply buy an AC/DC transformer that will give you something like 12v dc and then you can use a voltage regulator with an adjustable voltage.

If you want it to do everything, ie have 3 variable voltages each with variable currents along with meters that show what the voltage and current usage are, then I would recommend just buying a power supply. You will find that building your own power supply is much more complicated then you are probably expecting.

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You can have a look at this kit from tuxgraphics.

It may not have all the features yon want, but for a DIY power supply, it may be a good start.

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