Circuit running from PC Power Supply

Discussion in 'General Electronics Chat' started by happs, Mar 21, 2005.

  1. happs

    Thread Starter Member

    Feb 27, 2005
    Hey :)

    Ok, I got a question that has been bugging me over night :)

    If I was to make a circuit to put inside my PC and had say, maybe, some LED's n stuff working from it (from a molex connector), what would be the best way of dropping the voltage down to run the circuit ? Would voltage regulators be good enough ? I don't really wanna run the circuit off the native voltage of the PC power supply because I think it would be quite unstable and get pretty hot too! So what are your suggestions as to the easiest way of accomplishing say, a 5 volt supply to a circuit inside a PC ?
  2. Brandon

    Senior Member

    Dec 14, 2004
    You have 12v, 5v, 3.3v, 1.2v already coming off of the powersupply already.

    12v and 5v are on the molex connects, The rest are on the connector to your motherboard. Just take a meter and find em.

    If your using a regulator, you still running off of the PC power supply. Your still going to cause it to drop a cetain amount of heat, but to be honest, you don't need to worry about heat unless you running another PC fro the same powersupply. At MOST a led is going to need 50mA. 50mA * 1.7v (I pick 1.7 for a little higher on voltage for the diode) and we have a whopping 85mW., where as a good 3D graphics card can pull 50watts. I personally connected an addtional 3 CPU fans to get more aircooling for overclocking my linux box and they pull an addtional 3 watts. Its nothing.

    Trust the power supply. Is the PC voltages we're unstable, your PC would crash. The DC lines are more stable than anything you could build. Also, diodes are not that sensitive to any noise or isses on a DC line. Hell, you can run a diode on a 120VAC line of your house provided you step down the voltage.
  3. buddyengineers


    Mar 19, 2005

    Hi frnd..,

    Firstly to clear ur confusion.., PC supplies are SMPS's they are one of the most stable supplies ever used., also it is the load current tht decides as to how much heat will be dissipatd and as u said. u plan to jst drive LED's they draw amx of 20mA for proper glow.., so no probs abt tht also .., and finally solving ur prob completely., ur molex connector provides u 5v., so thts it.., Done and all ur probs solved.., COngrats

    And njoy working