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I am looking for an AC or DC output wall wart power supply that provides an isolated output and brings out the earth ground connection to the output.

Specs --

  • Either single output or bipolar output
  • Any voltage 7V to 18V (preferable 7V)
  • 100mA of current
  • Must be new and in production (no surplus)
  • Must have UL/CSA/TUV approval
  • Must be encapsulated or closed (no open frame designs)
  • Earth ground can be a separate connection or tied to the power supply return.

I haven't seen these made in a long while. All of the wall-wart type supplies that seem to be made are isolated and there is no earth ground.

Thanks for your help.

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They aren't common for fairly good reasons. Is there a particular reason you need such a supply? –  Mark Apr 23 '10 at 1:27
    
I am looking for a substitute for a Theremin power supply. This particular design works a lot better with an earth grounded supply. The design could be changed but I was hoping to use the original circuit. –  jluciani Apr 23 '10 at 3:32
    
Every Dell laptop power brick that I've come across has had a ground pin on the input side, and presumably has a negative ground. –  Brad Gilbert Apr 25 '10 at 15:05
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2 Answers

up vote 4 down vote accepted

The only places i've seen wall wart supplies with an earth ground terminal are on supplies built for the alarm system industry and normally only on the 16.5/24V AC supplies.

Here is an example

As to why you don't see them. The ground terminal on mains power is intended to be used to earth ground the enclosures of devices operating at mains, or high voltage. For example a blender with a 120V motor and a metal case. This prevents the chassis from ever being at dangerous voltages due to wiring faults or shorts within the product.

DC supplies normally have a floating ground that can be at a much different potential level than earth ground. There normally isn't a use for a earth ground in such systems. You'd have to be very careful with it to not cause a ground loop and grounding the chassis to the floating ground is normally done but more for emissions issues as unsafe chassis voltages aren't a concern in low voltage DC systems.

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The home automation and alarm industry is an area I had never thought of looking at for this type of supply. Thanks for the answer. –  jluciani Apr 24 '10 at 2:58
    
@ jluciani I haven't been involved in that industry in 6 or 7 years but commercial fire alarms used to run at 24V and code required earth grounded enclosures so you'll probably want to focus the hunt for an ideal unit in that particular area. –  Mark Apr 24 '10 at 3:58
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If you're still looking for this type of power supply, I know that the older arcade style Xbox 360 Power Supplies (yes, they aren't the wall wart type, but they're still a wart on the floor) have an earth ground on the output connector.

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