Convert a Computer Power Supply to a regular Power Supply

[TehYoyo]

Hey all,

Along with computers, I'm also very interested in photography.

A lot of times, lighting is needed for a scene, especially in studio. For that, lights are needed. But, they're expensive ($200+). So a lot of people make their own lights out of things like LEDs, etc.

I'm trying to make lights out of LED strips (Link here). For that, I need 12V DC power. I thought to myself "Whoah no way! PSUs output 12V of DC power!"

I'm not a good electrician (in fact, I know very, very little). Does anyone know how I might convert a power supply so I can hook up my lights (like a plug-and-play sort of thing).

I've read a few guides online, but I'm mostly confused about the outputs they're using (Link - what are the red things and how do they relate to LEDs?).

I can see in this guide that the blue wire is -12v and the yellow is +12v... could I just make a circuit out of that?

Thanks for the help,
TehYoyo

 

[Bobnova]

You'd want to just use the yellow (+12V) and black (ground) wires, -12v to +12v is 24v.

Your best bet is to wire the lights to use Molex type connectors (old HDD style), or to make adapters that convert whatever the lights want to Molex. Then you can simply jumpstart the PSU (ala Paperclip Test (see sig)) and plug them in.

If the lights draw a decent chunk of power you're going to want a PSU uses DC-DC secondaries, but there are tons that do that. Those PSUs are essentially 12 V PSUs with a pair of small PSUs inside that generate 5V and 3.3V.

The red connectors in that guide are the voltage outputs, he removed the normal PSU bits and replaced them with those. Personally I wouldn't do that, I'd leave the PSU entirely stock and just make adapters to turn Molex (and maybe PCIe) plus into whatever you need them to be.

 

[TehYoyo]

That makes sense, thanks Bob. Simple question, but I'm just making sure. +12v (Yellow) wire connects to the - side of the lights, right? Opposites always together?

Speaking of the voltage outputs, is there any way that I could hook up something like a car headlamp to the output? Plug-and-go? Maybe a single-prong H1 headlight?

Thanks,
TehYoyo

 

[Bobnova]

When connecting batteries in series, yes, but only then. When connecting things like LEDs, no. When connecting something with a silicon brain, wiring it + to - will kill it.

You can attach anything that runs on 12V, but custom wiring will be required for anything that isn't a PC part.

 

[TehYoyo]

When connecting batteries in series, yes, but only then. When connecting things like LEDs, no. When connecting something with a silicon brain, wiring it + to - will kill it.

You can attach anything that runs on 12V, but custom wiring will be required for anything that isn't a PC part.

I'm asking whether or not, if I group the wires and run them to a voltage output similar to the way this guide did it, and I plug the lamp into the appropriately-sized plug, will it work?

Also, in step 4 of that guide, he/she talks about how the PSU is 400 watts and how he/she needs all 9 wires for all 400 watts. Could I control the wattage (say I need 90 watts of power, or (400/9)*2) by only using two wires?

 

[Bobnova]

Yeah you can run any 12V device, doesn't really matter what, as long as it doesn't draw more power than the PSU can put out.

Wire wise, the PSU will deliver as many watts as the thing plugged in asks for regardless of how many wires are being used.
This can be an issue if you only use one thin wire and your devices demands a lot of watts.

 

[TehYoyo]

That makes sense. So you would use all wires so that you don't burn up a single wire.

Side question: How does the PSU divide up power? That is, how does the PSU know not to send power to a PCI connector that isn't plugged in? Does it?

Finally, how dangerous do you think this is? I obviously take all precautions when doing anything remotely connected to electricity, but I've had people tell me to not touch any of this stuff at all - I came here because I don't believe in that message. Are there precautions I should always take (rubber gloves, safety goggles, rubber-soled boots)? Is there anything I should/can do when I finally plug in the light to make sure? Should I get a multimeter to check it first?

 

[Bobnova]

I strongly recommend some time spent studying basic electrical theory before you dive in. That'll answer many of your questions in a nice linear way.

In the main time, what the PSU does is make 12V available. The things plugged in complete the circuit and allow it to flow.

Probably your best bet from a cost/time standpoint is to find a local hackerspace and see if anybody in there is willing to wire it up for you for some cash. That'll get it done right quick, and I seriously doubt it'd cost more than $40.

You will definitely need a multimeter.
Low voltage (12V and below) isn't dangerous unless you actively try to make it so.

 

[TehYoyo]

I strongly recommend some time spent studying basic electrical theory before you dive in. That'll answer many of your questions in a nice linear way.

In the main time, what the PSU does is make 12V available. The things plugged in complete the circuit and allow it to flow.

Probably your best bet from a cost/time standpoint is to find a local hackerspace and see if anybody in there is willing to wire it up for you for some cash. That'll get it done right quick, and I seriously doubt it'd cost more than $40.

You will definitely need a multimeter.
Low voltage (12V and below) isn't dangerous unless you actively try to make it so.

Thanks once again for all your help - do you recommend any books for basic electronics?

 

[Bobnova]

This guy is my favorite, it might be a bit dense just starting off, but give it a read.
http://jeelabs.net/projects/cafe/wiki/Easy_Electrons

The first Easy Electrons about resistance, or on the next list down "What is power?"

 

[TehYoyo]

I'll wade through those. Thanks.

I don't know where to ask electronics questions - any forums?

 

[Bobnova]

I'd give the EEVBlog forum a shot, seems pretty active at least.

 

[TehYoyo]

Thanks for the help. You can close this.