# 'puter power supply...help!



## Revenant (Mar 17, 2007)

I'm hacking a computer power supply, and I noticed that in all the instructables and stuff online that show how to do it, no one ever uses the orange wires. Is there a reason for this, or is 3.3V just not deemed very useful by most of the gadgeteers out there? Cuz that's a decent voltage to run LED's. I just wanna know if I should bother putting a post on for 3.3v or if I should just clip 'em off.

Also... I know that positive/negative voltages can be paired to get higher voltages i.e. +12/Grd=12 volts while +12/-12=24volts. But one site says that works by pairing the positive voltages too, e.g. +12/+5=7 volts. I understand the logic behind that but doesn't there have to be a negative or a ground involved to complete the circuit? Pardon my stoopiditty but I'm a real tech-noob just learning to shake off my Luddite ways...


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## .id. (Jul 3, 2006)

There's nothing wrong with leaving a post for the 3.3V....It will run LED's (may need a resistor depending on the LED) without a problem. Most people I've seen use computer power supplies for their abilities for providing high current in the 5V and 12V range for motorized props. As for using the +/- voltages combined, the lowest volage essentially becomes the negative (or ground) in the circuit. The only thing you have to watch for in those cases is that the other voltage you are using (particularly the -5V and -12V) have the required amperage to run your prop. (The -5V and -12V usually have much lower amperages than their positive counterparts and when adding voltages, the lowest amperage one will be the limit.)


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## heresjohnny (Feb 15, 2006)

I have user the +3.3 volts for a lower speed on a wiper motor.


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