I have created a circuit that can basically make a motor run in both directions using an on-off-on SPDT rocker switch and two relays.

Here is the circuit.

The catch is that this motor is 30 A at 12 V. That little rocker switch can only handle 5 A. I have highlighted the high current paths that the motor uses in red.

Could I use small gauge signal wire for the relays and switch, and thick high current wire for the motor current path without using a second power supply?

  • \$\begingroup\$ Yes, you can... \$\endgroup\$ – user253751 Jun 25 at 17:23
  • \$\begingroup\$ Why have you shown two relay coils in your circuit? \$\endgroup\$ – Andy aka Jun 25 at 17:38
  • \$\begingroup\$ For two relays. Apologies, edited question. \$\endgroup\$ – ElectronicsNoob Jun 25 at 17:40
  • \$\begingroup\$ Also beware the surge-start current on any DC motor = V+/DCR. Which is often 10x rated current at rated RPM thus reversing the voltage polarity has both the Vbat and Vemf being the same at steady state thus reversing it gives you 20x the steady state current and will burn out the contacts since you neglected this. 8-) \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 25 at 17:58
  • \$\begingroup\$ Relays I plan to use are 60 A automotive relays. If this still doesn’t work, is there a way to negate this? A soft starter maybe? \$\endgroup\$ – ElectronicsNoob Jun 25 at 19:24

Found a relay with 150 A inrush current and 40 A continuous. Found another motor that fits the same application that draws 9 A. Thanks for your helpful suggestions!

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