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If I have a few pins of a relay (which is rated for the correct current) that will carry 5A when the relay is triggered, what's the best way to wire this up?

Details: I have a breadboard with a circuit on it, but a small loop in the circuit will carry 5A when the relay closes. I want the pins that trigger the relay to stay on the protoboard, but obviously the breadboard can't handle that kind of current. I'm wondering what's normally done in situations like this, and what the different options are.

Thanks!

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  • \$\begingroup\$ Soldering heavier wire links, or metal bars, or even a thick layer of solder to reduce the resistances between points in that current loop could do very well. \$\endgroup\$ – Kenny Robinson Sep 21 '12 at 2:25
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If you are using one of those white plastic protoboards that has various series of holes that are bussed together 6 or 10 at a time then I would accomodate the relay as follows.

Place the relay with pins facing up and solder on short wires to the low current pins that want to go into the protoboard. For the high current contact pins wire with heavier wire as appropriate (for 5A you may consider 16 to 20 AWG wire) that connect off to your load. I've tried to depict this in the picture below.

enter image description here

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  • \$\begingroup\$ If the relay pins are long enough (and small enough diameter), you can also plug the coil terminals of the relay into the breadboard, allowing the high current terminals to hang over the edge. @Michael's sugguestion of soldering flying leads to the high current terminals still applies. Note that this can result in the relay coil terminals occasionally wiggling out of the breadboard, but in practice it's easy to spot. \$\endgroup\$ – HikeOnPast Sep 21 '12 at 4:16
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Michael's answer is a good one, and probably the way to go for a one off. When reading it though, a similar idea came to mind to maybe consider if you want something a little more "modular", the downside is a little more work to implement:

Mount the relay on a small piece of stripboard, and use a couple of 2.54mm pitch screw terminals for the power connections to the relay (or another detachable method, or solder wires in directly if you have nothing available)
Use a couple of 2.54mm pitch headers soldered to either (under)side of the stripboard to provide connections for the relay coil and support for plugging into the breadboard (the rest of pins can be redundant, just used for support - remember to cut any tracks connected to the relay power pins/header pins to isolate from breadboard. You may also want to add some solder/wire to the traces just to make sure they can handle the current)
Hopefully the above makes some sense.

This way you can plug the relay "module" into the breadboard and attach/detach the stuff you want to turn on/off easily.

OR

Buy a ready made module, but where's the fun in that... :-)

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