Blimey, mate, you do want the proverbial hen's tooth don't you ?
Most made were 4 or 8 channels.
However there is a work around.
While too expensive to use in big installs, you want a OPTO22 module.
http://www.opto22.com/site/pr_detail...=4&item=DC60S3
60 VDC 5 Amp model is optimum. Place a reverse diode across the GM20 coil to kill the back EMF and a 20 Ohm, wirewound, resistor across the coil for damping. Wire the coils in series if it is a 4 terminal GM20. The wirewound resistor, if used, can get hot, use a big un. Diode shall be a 1N4007 or larger.
When you buy the OPTO22 or clone, make sure its rated to switch DC, the AC ones are just a triac and won't switch DC off.
If I ever really, really, wanted to hurt some one, a GM20 pegged to one side with 12V and allowed to snap back and ring shocks the %hit out of you, huge voltage spike. Thus the damping diode to protect the relay.
The Opto22 family is optoisolated, so it keeps the spikes and failures out of the controller.
Steve
Last edited by mixedgas; 10-06-2010 at 09:02.
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