From: "Klaus Vestergaard Kragelund"
References: <6hKT9.5843$IC6.email@example.com> <firstname.lastname@example.org>
Subject: Re: VERY short range Proximity Sensor
Date: Tue, 14 Jan 2003 23:15:18 +0100
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Organization: TDC Internet
"Terry Pinnell" wrote in message
> "Neil" wrote:
> >Anyone have a schematic for a proximity detector that would be triggered
> >a hand being placed less than a inch from the antenna?.
> >All the ones that I find trigger from several feet away.
> >Thanks in advance,
> Here are a few possibilities, illustrating both 'capacitive mains
> pick-up' and 'capacitive change' types. The latter of course has the
> advantage of working well away from mains sources.
> Also, as an example of the capacitive change approach, see the circuit
> I used to make several touch-operated lamps at
> A couple of these are still working reliably 20 years later.
> The 'antenna' can be whatever you improvise: metal, foil, wire, parts
> of the lamp itself, etc. If working with mains voltages, of course,
> take appropriate care.
> In the basic form shown, no toggling is included, so it would be On
> when antenna was touched, Off when not touched.
> Terry Pinnell
> Hobbyist, West Sussex, UK
Anybode know what figures of capacitance change we are talking about. I
wounder if it would be possible to use an anlog switch array and a
microcontroller to keep taps on the frequency of each node to create a cheap
and simple keyboard?