Relay Circuit to Switch on Higher Amperage Project

patrickstefanski

Joined Apr 15, 2017
46
Hello. I've never really worked with relays before, so I was hoping for some guidance.
My project is a battery powered robot with a single motor that pulls about 5 or 6 amps. I want to use a power switch that is very small and rated for less than an amp.

The top image is what I'm working with now. 12v Lipo Battery which runs through a switch which goes into my microcontroller/mosfets/etc.
Can I switch this out for something like the bottom image? Where the batteries are hooked up directly to the switch AND relay. SO I can just hit the low-rated power switch and the relay completes the circuit? Where even if the motor is pulling 6 amps and the switch is only rated for say 500mah, it wont get fried?

If this is correct, can you recommend the most compact solution for the relay? One thing I lack is space for a large component in terms of height, which is what I see a lot of relays looking like. I can do long and flat. But Tall is tough.

Any help is very appreciated!

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Joined Jan 15, 2015
4,892
Will a common off the shelf automotive relay fit? That would be about 1 cubic inch. Any auto parts store has everything you need and most relays have a mounting tab with a screw hole. They also can easily handle 30 amps DC. The pins are standardized with a numbering system.

Ron

patrickstefanski

Joined Apr 15, 2017
46
I'll definitely try to make that work if that's the smallest option. Do you think that circuit would work as drawn?

Joined Jan 15, 2015
4,892
Pretty close to as drawn. Here is what you would have:

So pin 85 goes to ground or common. pin 86 goes to the light switch a normally open switch which then connects to 12 VSC power (Battery +. terminal 87 also goes to battery + and terminal 30 to your loads.The terminals are 1/4" spade lugs and yhe parts store will have mating connectors. Not much to it,

Ron

patrickstefanski

Joined Apr 15, 2017
46
Thank you so much!

Joined Jan 15, 2015
4,892
You're welcome and that should work for you.

Ron

If you have an automotive wrecker in your area, you can get a handful for a couple of 's usually.