Basic PSU Question

Discussion in 'General Electronics Chat' started by Metalmann, Mar 19, 2013.

  1. Metalmann

    Thread Starter Active Member

    Dec 8, 2012
    Since I'm starting out, (Again); I don't understand something that should be quite simple.

    On the power supply, you have a red, green, and yellow jack.

    I have never used the yellow jack. What is it's main purpose, and some easy examples, if you see fit?:confused:

    Thanks in advance!
  2. kubeek


    Sep 20, 2005
    On WHICH power supply? Mine is all black and with no jack.
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  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
    Measure the voltage (red to your red terminal and black lead to your green terminal). Then move your red probe to the yellow jack. Your meter should read a negative value that is about equal to the first measurement. If it works out as I said, then the yellow is most commonly used for the negative supply rails of op amps, audio amplifiers and any other project requiring dual rail power supplies. Not all op amps require dual power but most can use dual power if you have it.

    Colors of the jacks vary a lot. Black is commonly used for ground - since you don't have black, I assume your green is ground. Some supplies have a pair of AC jacks (usually in both jacks are yellow).
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  4. Jaguarjoe

    Active Member

    Apr 7, 2010
    Yellow could be anything at all.

    You'll need to see the manual for its intended purpose.

    Take the PSU apart and trace the yellow jack wiring.

    Empirically figure it out with a voltmeter and some sort of variable load.

    Remove the yellow jack, plug the hole and forget about it:)
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  5. Metalmann

    Thread Starter Active Member

    Dec 8, 2012
    I meant to, black, and yellow. Sorry.:(

    I've used the red and black to power things up. Mostly checking out large LEDs and DC motors. The manual, says yellow is the (outlet grounding terminal). Still don't know what use that would be for DC circuits.:confused:

    According to the manual:

    Black=Negative output terminal
    Red=Cathode output terminal
    Yellow=Output grounding terminal
  6. @android


    Dec 15, 2011
    Found on another forum:
    "It's connected to the ground pin in the mains plug. The power supply is floating, so if you want a grounded supply, you connect either the positive or the negative output terminal to this terminal, depending on whether you want the voltage to be positive and negative relative to ground. This is much more flexible than a power supply with a 'real ground', since you can freely put floating supplies in parallel/series. If you need +/- 15 V, you can take two 15 V supplies, connect the positive terminal from supply 1 to the negative terminal of supply 2, and to ground."
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