# 12VDC/120VAC PC Relay



## michael myers (Sep 3, 2007)

I am using a radioshack 275-248 12VDC/120VAC pc relay to complete a dc circuit to a pair of 10mm red leds wired in parallel for the eyes on my automated coffin(placed in the eye sockets of my sit up skeleton). When the A/C power is on this relay should complete the D/C circuit allowing both eyes to turn on, as long as A/C power is applied. Does anyone know if this relay is supposed to make that loud of a buzzing noise when the coil is charged? And, is the whole relay going to get really warm while in operation.
I have never used one of these before, and can come up with a way to dampen the buzzing, but I don't want a fire hazard in the makes!!


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## Brad Green (Jul 29, 2004)

I always use the 275-217 relay to control my prop functions. I'm not familiar with the one you're using, but you might get better results with the 217. It's a 120VAC relay and I've used it to pull on everything from LED's to fog machines with no problems, does'nt buzz or get hot at all. They run about 9 or 10 bucks, but the results and reliability are worth it. If the 248 gets hot, it's pulling resistance and could cause you a melt- down (or worse!)


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## BuriedAlive (Jun 8, 2006)

The buzzing is not uncommon. I've used relays that were so quiet I thought they were broken, and then I've used some that we so noisy they nearly drowned out the sounds on my props.


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## Death Master (Jul 1, 2007)

If you want to get rid of the relay chatter you can add a snubber circuit. Suppression of an AC relay is normally done using a snubber network consisting of a capacitor in series with a resistor in parallel with the relay coil.
I work with a lot of relays,contactors, and starters, and we add the snubber so we dont have the chatter problem.


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## michael myers (Sep 3, 2007)

I think I'm going to go try one of those 275-217 with the socket, but I am also going to get the cap and resistor for the chatter, just in case. I gotta go back to the ole ratshack anyway, broke the leads off one of the leds tracing the circuit last night(big fingers and small electronic parts do not mix!!!!) Thanks for all of the help!!!


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## MansionHaunter (Sep 20, 2006)

What voltage of AC are you applying to the coil? It's rated at 12v dc.


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## michael myers (Sep 3, 2007)

MansionHaunter said:


> What voltage of AC are you applying to the coil? It's rated at 12v dc.


Thats why the damn thing sounded like it was going to blow up, LOL!!!
I went ahead and got the 275-217 and it worked like a champ!!

Let's see, coffin finished...99 other things to get finished now!!!


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