Tried searching and didn't find quite I was looking for.
I have a 5v output that I need to use as a trigger for a 12v30a relay. I've been unable to find a relay that will pass 12v30a through but have a 5v coil, and I'm not sure how to properly wire up the transistors and resistors to make sure it doesn't explode.
Here are two options:
Get a 5vdc reed relay from Radioshack. You can run the 5vdc signal to the coil of the reed relay. Then, wire the coil of the 12vdc relay through the contacts of the reed relay.
Use a PNP transistor. Run the 5vdc signal through a ~500 ohm reisistor to the base of the NPN transistor (like a 2n3904). Ground the emitter of the transistor, and wire the relays (-) coil terminal to the collector of the transistor. You will want to put a diode across the coil of the relay (stripe facing the 12vdc side).
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Kevin Pierson
KPierson wrote:
Here are two options:
Get a 5vdc reed relay from Radioshack. You can run the 5vdc signal to the coil of the reed relay. Then, wire the coil of the 12vdc relay through the contacts of the reed relay.
I'll take that route as it seems easier, thank you.
I took a look at a reed relay and noticed that there seems to be only 2 connections possible on each side?
If it's not too much to ask, could you sketch a quick wiring diagram? Just want to get it cleared up in my head.
Thanks again
There should be 4 pins - two are the coil and two are the contacts.
Wire your 5vdc output to one coil pin, wire the other coil pin to ground.
Wire 12vdc to one of the contact pins, wire the other contact pin to the (+) 12vdc coil of your relay.
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Kevin Pierson
KPierson wrote:
There should be 4 pins - two are the coil and two are the contacts.
Wire your 5vdc output to one coil pin, wire the other coil pin to ground.
Wire 12vdc to one of the contact pins, wire the other contact pin to the (+) 12vdc coil of your relay.
Got it. Just seems weird this little thing can handle 12vdc from the car battery. Thank you very much.
It's not so much voltage you have to worry about as it is current. That is why I suggest you run the 12vdc 30A relay coil of this little guy. The current will be limited to about 150mA or so and won't hurt the reed relay.
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Kevin Pierson
KPierson wrote:
There should be 4 pins - two are the coil and two are the contacts.
Wire your 5vdc output to one coil pin, wire the other coil pin to ground.
Wire 12vdc to one of the contact pins, wire the other contact pin to the (+) 12vdc coil of your relay.
Alright, just got the soldering for the rfid finished. Couple stupid questions:
1.) How the doodie do I hook up a thick gauge wire to this reed relay?
2.) The 12vdc+ from the reed contact connects to 85 on the large relay?
thanks again for being patient with my ignorance
In a perfect world you would mount the reed relay to a PCB, then you could solder a small wire to the board that would connect to the relay wiring.
You would put 12vdc on one of the contact terminals and connect the large relays (+) coil to the other contacts other terminal on the reed relay.
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Kevin Pierson
KPierson wrote:
In a perfect world you would mount the reed relay to a PCB, then you could solder a small wire to the board that would connect to the relay wiring.
You would put 12vdc on one of the contact terminals and connect the large relays (+) coil to the other contacts other terminal on the reed relay.
