In my experience, what you are describing is best suited for a relay, but I
suggest
(1) that it be socketed (for easy replacement) and (2) you carefully
isolate the RF and other noise spikes that will result from your PIC
control device PCB. Wires going to and from the relay should be twisted,
and where they exit the card, should be ferrite-beaded and L-C (Low Pass
Filter) on each wire.

Be sure to provide transient protection across the relay coil, of course,
to protect the FET or transistor driving the coil. In the old days, people
used GP diodes or zener diodes; that is now considered bad practice, as
coil transients are too fast for the diode to clamp them down to an
acceptable range. Tranzorbers or varistors are fast enough and must be used.

Good luck.

--Bob


At 10:16 AM 8/15/2003 +1000, you wrote:
>Hi
>
>If you received this earlier my apolgies,
>I neglected the ":" after the topic
>tag.
>
>Hi People
>
>I am not sure if this is the correct forum or not.
>
>I am building a small system with PIC control which
>has to switch large currents +30A at 12/24V. The
>frequency is quite low i.e. once per hou. This
>is not really my area so I need some advice.
>
>Without wanting to start WWIII what do others
>see as the pros and cons of the various methods
>electronic and mechanical.
>
>Thanks for any input.
>
>Jon
>
>--
>http://www.piclist.com hint: To leave the PICList
>mailto:piclist-unsubscribe-request@mitvma.mit.edu

--------------
Bob Axtell
PIC Hardware & Firmware Dev
Tucson, AZ
1-512-219-2363

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