+/- Voltage Regulator Question

Discussion in 'The Projects Forum' started by loud41, Dec 28, 2015.

  1. loud41

    Thread Starter New Member

    Dec 28, 2015
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    I have been both going to school for and teaching myself about electronics, so I'm new to electrical theory. So please bear with me here.

    I am working on a radio that requires -6v DC @ 2.5A max, 1.5A continuous. The circuit of the radio uses a (+) ground. This has caused much head scratching and hair tearing out on my part for some reason because I am struggling with ground referencing. The radio originally ran using a 6v battery, the (-) pole attached to the power connection and the (+) pole connected to the chassis. The chassis also has a lug where a connection to true earth is supposed to be made or however you say it (the third prong on an AC plug if I may put it deftly as an example), but this does not have to be connected in order for the radio to work.

    My question is this: I want to replace the battery with a linear power supply. AC in, DC out. Problem is, everything I look at that's reasonably priced use (+) voltage regulators. Can I take a power supply that has no ground reference (no third AC prong) and uses a (+) regulator, and simply connect the (-) output to the radio and the (+) output to the chassis to have it work? Or do I really need a power supply that utilizes (-) voltage regulators?
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,030
    Normally any supply will work because the DC side is isolated from the AC side. Connecting either pole to ground does not cause current to flow under normal conditions.

    If you want to be extra careful, use a 1k resistor to connect the chassis to earth ground and look for a voltage. If not more than a few mV , step it down to 200 ohms and look again. As long as not much current is flowing, you're good to fully ground it.
     
  3. loud41

    Thread Starter New Member

    Dec 28, 2015
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    Alright so correct me if I'm wrong here. Are you saying it doesn't matter how I connect the power supply to the radio, or that it doesn't matter if the supply has a (+/-) regulator? I bought myself a pair of 6v batteries a while ago and connected them up to the radio. If I connected the batteries up (+) to the power connection and (-) to the chassis, the radio didn't work. If I connected the batteries up (-) to the power connection and (+) to the chassis, the thing fired right up. I just figured if I was going to connect up a power supply to the radio, I'd have to connect it in the same manor as the batteries. The (-) output to the power connection of the radio, and the (+) output to the chassis. (Not to argue, please! I'm just trying to wrap my brain around this)
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,093
    3,030
    Right, you still need to respect the polarity it wants. I just pointed out that grounding a chassis doesn't require it to be the lower voltage pole.
     
  5. loud41

    Thread Starter New Member

    Dec 28, 2015
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    0
    Ahhh, gotchya! Thank you so very much for your help!
     
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