Caution: Power Supplies!!

Larry Hendry jlarryh at
Sat Mar 21 01:00:25 CET 1998

Speaking from a guy that works daily with 12,500 to 345,000 volts, I can
tell you that more people are killed from 110-480 volts that from any of
the higher voltages.  The reason--lack of respect for the danger.

The skill at working with 110-120 volts is not to touch it when it is
energized (plugged in).  Now, this sounds like a simple concept, but one
that is often overlooked.  We may get lax about touching our "working"
circuits when dealing with lower DC voltages.  But, when dealing with 110
VAC, care needs to be exercised.  

Now, I am sure there are many stories from those who remember being shocked
from 110 VAC (I have a few of my own).  However, it is not to be taken
lightly.  Probably the one best thing you could do for your own safety is
to buy a GFI (ground fault interrupter) and plug your power supply into
that while taking readings and such.  They have these available in many
1. A breaker for your circuit box that puts the whole circuit on the GFI.
2. A replacement outlet (great for the workbench outlet)
3. Extension cords with GFI built into the end (great for working outdoors
with power tools).

A GFI breaker will trip when you are being shocked (any small amout of
current going to ground) when a regular breaker will not.  So, protect
yourself when working on energized circuits (when you must) and invest $15.

Personally, I have a set of 600 volt dielectric gloves I wear when working
with power line voltages
Larry Hendry

> From: Milliams <Milliams at>
> To: Synth-DIY at
> Subject: Caution: Power Supplies!!
> Date: Friday, March 20, 1998 1:45 PM
> Most books I've seen for modules n'stuff, recommend that I start building
> +/-15v power supply. But somewhere in the design it says "Caution: If you
> unskilled at working with 110v AC, do not attempt this project!!". Well,
> it is logical to start with the power supply, how do I become "skilled at
> working with 110v AC"?
> Sincerely,
> A cautious (don't wanna die!!) boy

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