I have a remote control dog shock collar.  I want to hook the
transmitter up to my computer so that I can schedule an electric shock
to wake me up (alarm clocks don't work for me).  What I need is some
sort of way to use a port (probably the serial port) to complete a
circuit, that is, act like a switch.  What sort of wiring do I need to
purchase, and can I do this through a batch file or do I need to
compile a C++ or Visual Basic program?  I am running Windows XP Home.

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Request for Question Clarification by endo-ga on 05 Nov 2004 15:38 PST

Hi,

An easier solution would to use a cheap alarm clock (Radioshack under
$10), remove the speaker and hook the speaker wires directly to the
collar.

Thanks.
endo

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Clarification of Question by fundamental-ga on 05 Nov 2004 22:32 PST

Perhaps, but that's much less customizable.  I'd like to know how to
do it through my serial port.

Take a look at the image "Serial Monitor Cable" at
http://www.jspayne.com/io/schematics.html.

Two things to note: CTS is tied to DCD (this is important!)
and it's listening on pins 2 and 5... so get out your multimeter in
both Voltage and continuity mode and check what happens when you
echo "A LONG MESSAGE"> com1

You *might* get a Write Fault Error if DSR isn't tied high as well.
Your results may vary. Check out http://www.airborn.com.au/rs232.html
to make sure your serial connector is looped back properly... all you
want to know is that you can send from Windows "error free". With the
loopback proper, you only need to monitor your TX/GND from the PC.
However, your transmitter might not like the voltages presented by the
serial port. To be safe, you might just want to use a relay that can
be powered by as little as 5 volts, but can handle up to 15v (the EIA
spec range). Radio Shack's Compact 5VDC/1A SPST Reed Relay Catalog #
275-232 $2.79 is a nice choice, but it can't handle more than
7.5volts. Check with your voltmeter to determine your computer's
voltage on the serial port when TX'ing.

I hope this free comment helps.