# Making your own Power supply?

Discussion in 'The Projects Forum' started by Mathematics!, May 15, 2009.

1. ### Mathematics! Thread Starter Senior Member

Jul 21, 2008
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I am wondering what bridge retifier I could use to convert house 120 AC to 120 pulseing DC. Then what regulator/capacitors I need to smooth it to 120 DC. Then what resistors to drop it to 12 volts.

I have resistors but they are either 1/8 , 1/4 , 1/2 , 1 watt in any of the sizes. I don't think these would beable to dissipation the heat under house voltage.

Curious to know if their is anyway to get the retifiers and regulators that would convert house AC to DC. And maybe a potientometer to vary the voltage. Locally at a radioshack ....

Thanks for any input

2. ### DonQ Active Member

May 6, 2009
320
11
It is clear from your question that you do not have much (any) experience with this sort of thing, so you should not be playing with 120VAC. It can kill you.

Besides, this is not the way to do something like this. Get a transformer that will convert the 120VAC to something closer to 12VAC, rectify 12VAC (you'll get about 17V DC), and then play with that.

Playing with 120VAC is a very bad idea.

3. ### steinar96 Active Member

Apr 18, 2009
239
4
i'll have to second that last post. You are best off getting a transformer to transform 120V to 12V AC. Then rectify the 12V AC input to DC.

Apr 5, 2008
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5. ### Wendy Moderator

Mar 24, 2008
20,772
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My personal thought on the next power supply I make (and I have made several bench variable supplies for my own use) is to get a large wall wart or module, and go from there. Even a digital supply, with lots of noise, can be quieted pretty easily.

I've seen several posts where people made variables using LM317. That was the route I chose for my second supply, I made it around 30 years ago and it still serves me well.

Here is a basic power supply. The part I left off was the fuse and switch from the hot side. I am cautious with high voltage (to say the least). Really high power electricity can literally explode if you short it, in the form of plasma, for up to 10 or more feet. It's what makes being a line man one of the more more dangerous jobs out there. With house current you usually make a good looking corpse.

My own feeling is make one, but be careful. It is how we learn. The first power supply I made was while I was in high school.

6. ### beenthere Retired Moderator

Apr 20, 2004
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All the above cautions are strongly agreed with. Never try to work with line voltage unless you have a transformer to isolate you. No circuit that runs off the line can be made safe - it is always a lethal shock hazard.

You can get wall transformers for a couple of bucks, and apply the output to an LM317 for a variable power supply.