# A Simple Power Supply.

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## Introduction: A Simple Power Supply.

OK, I had this plug-in charger going spare. I'd bought it to replace a lost power-supply for a car DVD player, but it wasn't up to the job.

Time to give it a new lease of life.

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## Step 1: Oh, It's *so* Hard to Make...

I lopped off the useless jacks, split the wire, stripped the end and soldered on the crocodile clips.

It was nearly as quick as it took to type this step.

## Step 2: The Interesting Bit.

OK, so I have a cheap power supply (the charger cost me Â£2.99), so what?

Ah, because I can choose the voltage! It's a bit hard to see in the photo, but there's a sliding selector for anything from 0V (why??) to 12V, and a little recessed switch to swap the polarity as well.

One "problem", the voltage on the scale is wrong - a voltmeter across the crocs reads about 50% higher than the number on the scale. The working voltage is actually 4.5V - 17V.

It's not just a toy, it's been used in anger, to test the bread-board circuit for the version of Minty Beating Valentines Heart I'm part way through (https://www.instructables.com/id/EG7BX7AVJ7EXCFLX7K/ - I'm just looking for a suitable box to land a dragonfly on).

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## 22 Discussions

You are wrong about the volts out.The voltage will drop when you load some charge in.These supplies normally are not stabilised.

Good idea. You also might want to make one leg of the "wire split" a bit shorter than the other to help keep the two clips from accidentally coming together when not clipped onto whatever you are powering up.

Good thought (although the little green sparks are fun...)

Question, I have a fan from a computer, can I use a the above adaptor to convert into an AC fan? What would the necessary output requirements be on each? Thanks in advance.

Yes, you can (I do). I did nothing to the fan except rip it out of a dead PC.

Just check that you aren't massively over-powering the fan (although I think most PC fans are 12V).

Excuse my ignorance, but how would I know if I am "over powering it"? What should the ideal output be on the plug converter be? Thanks in advance, I need to use something like this for a fan in a bathroom.

Read the fan, see what it says it needs, and read the power supply (wall wart) to see what it puts out. You may be wasting your time, though - a single PC fan will not be able to ventilate a bathroom well enough to prevent condensation or mildew.

Actually one of my wall wart transformers says it puts out 12volts DC but it really puts out closer to 18?? (without a load on it)

As others have pointed out, a lot of these are not regulated properly, and they only give the correct voltage through a load.

Umm.. I built some air purifiers that required some computer fans and all I did was get an old wall wart (12volt) transformer and cut off the ends, attach it to the ends of the fan wire (I cut off the molex first!) Plug it in and your done!

The detail that you need to look at on this power supply that relates to all the available voltages is the VA (volt-amps). This number determines the max current draw at any of the voltages. To determine the current the basic way is to divide VA by the voltage. The VA is 3.6 and for example at 12 volts would be around 0.3A which is also printed on the power supply. However if you wanted to set it at 5 volts your current would then be about 0.72 A. Also remember that this is only an AC to DC power supply. The 12V fan that littleangelss wants to use on AC really is only being supplied by DC or at least pulsating DC.

hook it up and read the current again. there is a great difference in a plugged and an unplugged reading. this is cool. and it works. i clip it to my dog's butt. he wiggles a lot!!!!

As LasVegas I don't think these things are regulated in anyway, so load affects the voltage a fair bit. Just 7 different taps off the same transformer, some recification, and small smoothing cap' I suppose.

I had one of these exact same ones and yes they are, as you stated, a simple rectified and smoothed, non-regulated power supplies. Personally, I would not let this power supply charge any of my gadgets at all.

hmm. cool, but my variable plug adaptor thing has like all sizes i need and it has built in aligator clips :D (its like a ghetto older one thats got like every plug youll ever need on it, plus some)

i have so many rubbish plug like this in my home...thank for your "invention"

Oh man, those adjustable ones are so handy. Too bad I just fried/melted mine, by hooking it up to a 6v dry cell to power a floppy disk motor (which I couldn't get too work). I smelled something plasticy and burning and I had to chuck it. WAHHH!

I noticed I had an almost identical plug in my draw, so thought I'd take a close up picture for you. Just to add to the clarity of your instructable.