> If I understand you correct, you want to leave the diode on the pcb,
> but move the relay remotely.  I would think this is okay since the
> original purpose of the diode is to protect the circuitry that drives
> the relay, and it can do so on the PCB.

I would put a diode in both places if the relay is far from the driver.
The diode at the driver should protect the circuitry, but the one at the
relay will cut down on large voltage spikes that cause RF, capacitively
couple into other circuits, etc.

> Now, not to open a can of worms here,

Then you continued anyway?

> but I read somewhere (some mfgr's
> tech doc, IIRC) that coil protection diodes may be great for the driver
> circuitry, but bad for the relay,

The reverse diode will cause the magnetic field to decay more slowly.  If
the relay coil and diode were theoretically perfect, then the field would
never decay.  In practise, the forward voltage drop accross the diode and
the DC resistance of the coil will dissipate the energy.

In most cases, this is probably not "bad" for the relay.  With the right
load and contacts, it might increase the duration of arcing.  For faster
turnoff, put a resistor in series with the diode.  Since the maximum relay
coil current is presumably known, you can size the resistor for the
maximum reverse voltage you can tolerate.


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