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Components I have:

  • Relay (rated at 12 V, 70 A, can't find how much current is needed to saturate its coils). Schematic here
  • Arduino Mega and Nano
  • 12 V Powerwheels battery + AA battery packs
  • Motor: 00968-9015
  • Transistor: PN2222
  • Diode: 1N4007
  • Appropriate wire, terminals, crimper, etc.

I need help wiring the setup in the title. I am trying to control a DC motor taken from a Powerwheels Jeep Wrangler through the pins of an Arduino.

The motor draws 70 A under normal load, and is brushed. I've been doing a lot of research online trying to understand how this would work, but I haven't found anything exactly like mine and do not quite understand how it should work. Namely, how do I connect the Arduino, transistor, diode, and battery to the relay that I have?

I should be fine with the code, like setting the pins to HIGH, it's just the wiring that is troubling me. I also am not sure if I will be able to reverse the motors' rotation with this (without an H-bridge or an expensive motor controller). Any help would be much appreciated.

Here are some resources I have been looking at:

http://henrysbench.capnfatz.com/henrys-bench/arduino-output-devices/tip122-arduino-relay-tutorial/

https://www.element14.com/community/thread/38334/l/car-relays-to-use-in-projects?displayFullThread=true

http://www.bcae1.com/relays.htm

https://itp.nyu.edu/physcomp/labs/motors-and-transistors/using-a-transistor-to-control-high-current-loads-with-an-arduino/

Here is where I got the figure for the motor's current draw.

Here is the Jeep Wrangler toy.

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  • \$\begingroup\$ I have no idea what a Powerwheels Jeep Wrangler is but using relay control for a 800+ W motor isn't going to work well. You will have terrible arcing and jerking of the motor. You need a DC speed controller. You can use a relay or heavy duty switch for forward / reverse but you'll need to inhibit the speed controller in software for some time to ensure that the motor is stopped before changing direction. \$\endgroup\$
    – Transistor
    Aug 4, 2019 at 19:43
  • \$\begingroup\$ Welcome to the site. It seems you are looking for a complete system solution, which unfortunately we do no supply. Even if somebody would supply a complete diagram, what you are trying to build is rather complex and I would not recommended working with 800W motors unless you have a lot more experience as the devil is in the details. Again, a warm welcome to the site. \$\endgroup\$
    – Oldfart
    Aug 4, 2019 at 20:18
  • \$\begingroup\$ 70A at 12V (1.1HP) seems a bit on the high side for those toy toddler-ride-'em cars. Where did you get that figure from? Seems high even for LRA. \$\endgroup\$ Aug 4, 2019 at 20:29
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    \$\begingroup\$ @ChrisStratton Oh okay thank you! I measured its resistance with a multimeter and got a value of 90 ohms, so that means I need 0.13A if I calculated that correctly. Well that's one thing checked off the list. \$\endgroup\$ Aug 4, 2019 at 21:32
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    \$\begingroup\$ BEWARE: The first link given (capnfatz) wants to download and install something to the browser!! \$\endgroup\$
    – PStechPaul
    Jan 24, 2023 at 10:42

1 Answer 1

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The relay information given indicates that is is intended to control a blower motor. A relay like that, as used in a car, may have its own fuse. If you can identify the blower motor fuse in one of the vehicles that the relay can be used in, that would tell you the maximum current required to drive the relay.

You might find a seller that sells it for general use. Such a seller may give more complete specifications rather than a list of compatible vehicle applications. Some sellers show a photos of their products that have sufficient detail to read the manufacturer's information printed on the product. From that you may be able to find more complete specifications.

A relay that is intended for starting and stopping a dc motor should be able to withstand the arcing. The motor should be able to withstand full-voltage starting if it is a motor that is sold for a use in which that is the normal starting mode. If full-voltage starting in your application produces an unacceptable jerk, you could make a reduced-voltage starting circuit using one or two series resistors that are shorted out as the motor accelerates. That may or may not be less trouble and expense than using an electronic speed controller.

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  • \$\begingroup\$ [load] fuse [would tell] the maximum current required to drive the relay How? \$\endgroup\$
    – greybeard
    Jan 24, 2023 at 9:29

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