A good 5v 'load' for a DIY power supply?

[XXWoodmanXX]

Alright, so after a first failed atempt at building a PSU from a debunked comp's power supply, I decided to give it another go. This time, success!

http://i27.photobucket.com/albums/c167/roy_woody/DIYPSU.jpg

Only problem is, I'm now realizing that you need a pretty decent sized load on the +5v line to keep her running, or it shuts down under a heavy +12v load (from my charger) I found that, when I dial my charger anywhere past 3.0A charge, the PSU shuts down. I would only assume that you just need a stronger load on the PSU's 5v line, right? So I built myself a peltier exchanger out of a 20w 5v peltier, and 2 old heatsinks.

It all well and good, but here are the issues that are arising:

- Lugging around a peltier with fragile leads on it.
- Condensation!!!
- needs cooling or it's own transistors will begin to seperate and ultimately, fail.


My question is, can someone think of a good +5v DC load I can put on this thing that will draw more than 1 - 1.5 amps? I want something that is portable above all else.

[adamzty]

:confused:I dont think the 5v line has anything to do with the 12v line. I have made a few of these and I just use the 12v and ground line, I dont do anything with the 5v line. Is it a ATX power supply? Does it say how much amps it on the 12v line? If it is ATX, you will need to connect the green wire to a black wire, and the orange wire (3.3v) to the brown wire for it to work.

Hope this helps:D

[adamzty]

I just looked at the pic again and I noticed something. Are you using all the black wires and all the yellow wires or just one of each? And the red wire from the deans is connected to yellow wires right?

[guver]

I use a 6 volt auto tail light (use both dual filaments)

The voltage may sag quite a bit as the current goes up.

[shujin1021]

It is a power supply that supplies power. So just use some basic equations to find a reistance that will pull 1-1.5 amps. P(power)=I^2(current squared)*R(resitance), V=IR, P=IV. So IV=I^2*R, R=V/I. R=5 Volts/ 1 Amp. Just stick a 5 ohm resistor over the terminals. You might want to find a big resistor too. Don't get one of the small ones, look for something that is atleast rated at a 1/2 watt.

[shujin1021]

Oh and usually when companies make these power supplies, its really a voltage source that is rated at a certain amount of amperage. So the one you would buy form LRP or who ever will give you an amperage rating. That is how much current it can safely supply at 12-15 volts. Remeber P=IV. so 12 volts* 7 amps= 84 watts of power. These supplies are very easy to build you can look for voltage supply kits on the web and you will find one to build. I have built one out of scratch before. All they normally consist of is a transformer, bridged rectifier, zenner diode, and a couple capacitors to fitler out any noise over the line. The power supplies that computers use are more complicated and usually have some more gadgets in them. I would not suggest using it to power your charger.

[adamzty]

Why not use a PSU to power a charger? Thats all I have used, and it works fine. And I had a few computer power supplies laying around, so why go out and spend 50 bucks on a power supply when I could have almost the same thing for free?

The only bad thing about them is that they supply exactly 12 volts, whereas some other power supplies will do 13.4v like a car battery.

[shujin1021]

Free is free, I will give you that. I would probly just build my own though. But then again thats just me. If you need 12 volts then why are you worried about the loads over 5 volts.

[BigBlock61]

Here is a link to making you're own psu. Look at the link for ATX differences. You need to put a resistor inline on the green wire to make it work. I have 2 that I've done and they work great.

Click Here (http://reckerclub.tripod.com/id105.html)

[chewie]

roy why did you have issues with yours ? i dont have a load on mine.. i just combined all the black wires and all the yellow wires and soldered leads on em.. and the power supply works fine.

[adamzty]

roy why did you have issues with yours ? i dont have a load on mine.. i just combined all the black wires and all the yellow wires and soldered leads on em.. and the power supply works fine.

Thats exactly what I did with both mine, and they work great...

[stanmondz]

how many amps can a homemade power supply put out?

[guver]

It could be nearly anything. Most of the converted pc power supplies will do around half of the rating plate. Some may do what they're rated.

[adamzty]

depends on the quality of the power supply. Usually around 10 amps 12v, but if you spend a little money and get a nice one, they can do up to 20 amps...