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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 ---You are limiting current with the resistor on the other side of the coil because you haveoyn series with the LED. so make sure that the value is proper to run both the LED and the relay.  I think the relay needs 20ma from the specs I looked up.

Also, make sure the LED is connected properly.  If it's backwards, the relay won't work.

RandyT

--- End quote ---

Thanks for all the help Randy!
One last question (then I'm done, I swear). I'm not too good at figuring correct resistor values, so what if I removed that resistor and LED completely, what would I connect relay point B to on the LED driver circuit?

RandyT:

--- Quote from: SirPoonga on June 14, 2005, 05:18:02 pm ---Thinking about it, wouldn't a capacitor inline on the switched circuit supress spikes?

--- End quote ---

A capacitor will help to protect the contacts of the relay by reducing the arcing that can occur when the contacts are opened and closed a lot.

This is usually only a problem when there is a lot of current flowing through the contacts.

RandyT

SirPoonga:
Cool, tha tmakes sense.

So, to answer my other question.  This is the relay I need if I want something from my computer, which most likely will be a 5V source, to trigger the 27V pinball solenoid?
There's a radio shack on my way home.  I might see what they have for power supplies too...

RandyT:

--- Quote from: JoyMonkey on June 14, 2005, 05:26:18 pm ---One last question (then I'm done, I swear). I'm not too good at figuring correct resistor values, so what if I removed that resistor and LED completely, what would I connect relay point B to on the LED driver circuit?

--- End quote ---

You may want to put a current limiting resistor in between the B connector and ground.  I'd try about 150ohm for starters and see if it works.  It may not be necessary, but I don't know enough about that relay to know for sure.    The specs I saw called out a 20ma switching requirement, so limiting it to something around there would probably be a good idea. 

BTW, don't blame me if it goes *poof*, this info is "AS IS".  But I'm telling you what I would do in this situation and would be comfortable doing ;).

RandyT

RandyT:

--- Quote from: SirPoonga on June 14, 2005, 05:30:23 pm ---Cool, tha tmakes sense.

So, to answer my other question.  This is the relay I need if I want something from my computer, which most likely will be a 5V source, to trigger the 27V pinball solenoid?
There's a radio shack on my way home.  I might see what they have for power supplies too...

--- End quote ---

According to the specs on the relay (for some reason, I think the ones you posted are different than the ones I got from the RS website) it should be fine.  But I would recommend the diodes and a capacitor for that setup.  You'll be driving an inductive load with a fair amount of current, so better safe than sorry.

RandyT

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