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Relay question (adding relay to Oscars LED driver board) - it works!

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JoyMonkey:

--- Quote from: RandyT on June 14, 2005, 04:48:36 pm ---Do you have a meter?

You should get continuity between the 2 coil leads.

RandyT

--- End quote ---

Why didn't I think of that!!???
I checked and AB is closed, CD is open

So this means I've got it wired correctly, right?  :o

SirPoonga:
Would it also be wise to put a diode across the switch of the relay to not allow feedback on that circuit?
I have to find my parallel port circuit again when I was looking at making my qbert knocker.  There was a spike protection circuit on it because relays are notorious for creating spikes when triggered.

RandyT:

--- Quote from: SirPoonga on June 14, 2005, 05:03:59 pm ---Would it also be wise to put a diode across the switch of the relay to not allow feedback on that circuit?
I have to find my parallel port circuit again when I was looking at making my qbert knocker.  There was a spike protection circuit on it because relays are notorious for creating spikes when triggered.

--- End quote ---

That's what the diode is there for.  IIRC, when power is removed from a coil, the magnetic field collapses and a spike can feed back and damage the circuit.

I think these are referred to as "snubbing" diodes.

(apologies to the EE types if I explained this wrong.)

If you were driving a solenoid (another coil) with the relay, a diode on the switched line would probably be a good idea to help protect the PC power supply.  I don't think a CCFL is an inductive load, so it's probably not a problem here.

RandyT

SirPoonga:
Right, but I thought (I need to find that schematic) there was a diode or some sort of spike protection on the switch because when that switch is closed a spike can occur.

I know the diode across the coil is there to prtoect feedback from the coil.

Thinking about it, wouldn't a capacitor inline on the switched circuit supress spikes?

RandyT:

--- Quote from: SirPoonga on June 14, 2005, 05:18:02 pm ---Right, but I thought (I need to find that schematic) there was a diode or some sort of spike protection on the switch because when that switch is closed a spike can occur.

--- End quote ---

That would probably be for inductive loads.  I updated my post while you were typing ;)

RandyT

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