# DC power supply?

#### python01

Joined Sep 20, 2007
2
Does anyone have schematics of bench top DC power supply? One which can be adjusted to different voltages and used to power stuff for testing. Good ones are really expensive so I am hoping I can make one myself cheaper.

#### niftydog

Joined Jun 13, 2007
95
Take into account your time as labour and you'll quickly discover those "expensive" ones start to look pretty cheap!

I'm looking at two here in Australia;
0-30V @ 3A
3-30V @ 20A
Both are only AUD$200. I contract myself out at AUD$65/hour, so if I could research, buy, build and test a similar product in 2 hours (which is impossible) I'd probably only just be in front.

#### beenthere

Joined Apr 20, 2004
15,819
Got any specs in mind?

#### Distort10n

Joined Dec 25, 2006
429
If you want a really cheap one, then you can use a computer PSU. At minimum it will not be adjustable - voltage or current wise.

#### python01

Joined Sep 20, 2007
2
specs, would be something most useful, assuming some circuits would be digital and some might be running at 24V most likely 0-30VDC @ 20A?

#### bloguetronica

Joined Apr 27, 2007
1,540
This forum has schematics for a double PSU from +-2V to +-13.5V and with 1.2A. See the "Projects Collection" section.

#### arthur92710

Joined Jun 25, 2007
307
If you want a really cheap one, then you can use a computer PSU. At minimum it will not be adjustable - voltage or current wise.
Thats what I did.
But i took it out of the cramped psu and put it in a big coffee can. I put a power led a toggle switch, 120v ac outlet, and two fans one in the center and one on the bottom (fans from the psu)

At first it only had 0 +5 +3.3 +12 -12 and -5. Then i got a pot and 7812 and now i have -5 to +24 but its extreamly sensitive. the voltage varies greatly so i will get another voltage regulator and have one give me -12 to 0 and the other 24 to 12/0

when my friend saw it he was like "how'd you build a nuke?"

#### ixisuprflyixi

Joined Sep 16, 2007
52
you could try something like this. http://www.hobbytron.com/UK400.html then all you need is an enclosure. There are plenty more kits like this if this particular one is not within the spec. you want.

#### mozikluv

Joined Jan 22, 2004
1,435
you didn't mention if the psu you need is single rail or dual rail. however if you need a single rail i can suggest an adjustable regulator such as the LT1083CP which is capable of giving a minimum output of 1.5vdc and a max of 28.5vdc at 7.5A. since you also mentioned a possible current capacity of 30A, then you can parallel 3 of these device. it comes in a TO3P package.

am attaching the datasheet of this device

moz

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#### thingmaker3

Joined May 16, 2005
5,083
most likely 0-30VDC @ 20A?
0-30 VDC @ 5A would be a "beginner" project. 20A is more tricky. You'll need either a switched mode power supply or a trick I have not yet learned.

Gottlieb's Power Supplies, Switching Regulators, Inverters, and Converters from Tab Books may prove useful.

#### bloguetronica

Joined Apr 27, 2007
1,540
0-30 VDC @ 5A would be a "beginner" project. 20A is more tricky. You'll need either a switched mode power supply or a trick I have not yet learned.

Gottlieb's Power Supplies, Switching Regulators, Inverters, and Converters from Tab Books may prove useful.
By my experience, even a 5A power supply, assuming that it will be regulated and not switched, will be very bulky. You have to build a capacitor bank for proper supply filtering, and would be a big and expensive one. I would consider a switched mode for a 5A supply.

#### GS3

Joined Sep 21, 2007
408
Does anyone have schematics of bench top DC power supply? One which can be adjusted to different voltages and used to power stuff for testing. Good ones are really expensive so I am hoping I can make one myself cheaper.
Define "stuff". You can power most small electronics with a power supply which will supply, say, 3~15 V and 0~2 A and you can probably buy one cheaply or build it from close to nothing using scrap parts. (During a recent trip to China I bought a very complete one like this with dual digital displays, regulated in volt and amps, for about \$8.) I have several crates full of old power supplies from electronics which I disposed of but kept the power supplies. Many can be used as they are or adapted with minor changes. Others can be used for parts. Building a simple, linear, power supply like this is a good learning experience and provides you with a basic good tool. You can use an integrated circuit or use discrete components.

For anything larger I would recommend going to a switching circuit and it can get complicated for a beginner. You can build a linear PS for 4~5 A but it is unlikely you will have a free transformer at hand, etc so it makes sense to go to a switching circuit.