Re: AC Proximity Detector

monolog99@xxxxxxxxx wrote:

Hi,

Out of curiosity - how do those hand held AC proximity sensors work ?
(e.g. the pen sized devices that you hold near to a live mains wire
which light up when AC is present). Is there an off the shelf IC that
you can purchase to make one yourself ? Anyone have a circuit diagram
for one ?

Reason for asking, I want to build an electronic circuit to detect the
presence of 240v in a wire - without disturbing the wire.

Many thanks,
Tim.

Electrostatic charges are on the surface of the wire.
Those simple probes you're thinking about are just hi-z
input sensing circuits via a couple of diodes to rectify
charge on the surface so it can drive a CMOS or FET type
sensing circuit. Normally input load are tailored to work in the
desired range and maybe a clamping protection diode to save the
day.
Electricity produces charges on the surface of the conducting
material.
If you would like a PDF file on the subject of how electricity flows? I think I may have something designed for students. You can email me if you wish.

--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

.

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