I've got a 12V DC winch motor with two field posts and an armature post (compound motor). Currently direction is controlled by four solenoids.

Solenoid direction control

Here's a diagram which boils this down two the two modes: Testing Diagram

I think speed can be controlled via PWM, but the standard H-Bridge most brushed DC motor controllers come with doesn't seem like it would support this configuration.

  • \$\begingroup\$ You've asked a shopping question at the end. This is a 'no-no' and will quickly get your question closed. Change it into a design question. \$\endgroup\$
    – Transistor
    Jun 14, 2016 at 20:21
  • \$\begingroup\$ How do you know that it is a compound motor? Where is the paralell feild connected? \$\endgroup\$
    – Autistic
    Jun 14, 2016 at 20:57

2 Answers 2


If you were to keep the solenoids for direction switching, you should be able to use a single very-large MOSFET for speed control.

Although the best place to do the PWM control is in the ground lead of the armature, that node probably isn't available to you.

So: setup a MOSFET and its driver as a floating switch and place it in series with the hot end of the armature.

Alternatively, place it in series with the battery (+) lead that feeds the solenoid contacts.

Doing a floating MOSFET power stage isn't difficult and your PWM frequency can be fairly low - low hundreds of Hertz.


You don't need a H-bridge for this application. You just need a heavy duty 12 V motor speed controller or PWM switch in the +12 V line.


simulate this circuit – Schematic created using CircuitLab


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