[Soekris] How to drive external relays?

[Poul-Henning Kamp]

In message <474B3015-BCB4-42FD-8007-02452B71054D at kivasystems.com>, Joshua Chait
inPollak writes:

>> Has anyone ever used a soekris box to drive a set of small relays?   

Yes, I've done a lot of such stuff.

You need driver transistor between the GPIO pin on the soekris
and the relay, here is a simple guide:  go for the NPN version:

	http://www1.jaycar.com.au/images_uploaded/relaydrv.pdf

Many people overlook the advantages of bi-stable relays in control
appplications, so I'll make a pitch for them here:

A bistable relay works like many push buttons do, first time you
push it switches to on, second time it switches to off, etc.

The advantage to these is that they retain the contact position
even if the controlling equipment looses power and they use
less power themselves because the coil is only energized when
you want to change the position.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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Never attribute to malice what can adequately be explained by incompetence.