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I have a basic hobby ESC connected to a motor, and the ESC inherently is unidirectional (without firmware changes, which I am trying to avoid). Is it possible to wire up 4 MOSFETS to two of the phases of the ESC to make a sort of "H-Bridge" circuit that electronically switches two of the phases.

If the above method is possible is there a need to use flyback diodes on each of the phases? Here is the MOSFET in question: IRFZ44NPBF.

I intend to control each of the MOSFET's through software on an Arduino or RaspberryPi.

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  • \$\begingroup\$ possible but not obvious. One could use a DPDT relay to the motor with active coil for reverse direction. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 31 at 17:43
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    \$\begingroup\$ A brushless motor uses THREE wires so you cannot use an H-bridge. An H-bridge is for brushed motors. However, the normal way to swap direction on a brushless motor whose ESC only allows a single direction is to swap any two of the three motor wires with each other. So you can use a DPDT relay as previously mentioned to do that. MOSFETs can't be substituted in this case without significant work due to the bidirectional nature of the currents in the motor phase wires and MOSFETs can only block current in one direction. You would need back-to-back common source MOSFETs pair with float gate drive \$\endgroup\$ – DKNguyen May 31 at 17:59
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This would not be realistic; and even if you could do it, you'd be increasing the losses in the 2nd set of FETs. Your insertion may also cause problems for the back EMF detection scheme.

Open source firmware is available for most ESCs and generally offers better performance than the factory version (except those that already come with it). You'd be better of doing this and implementing reversing in software, where it's a simple logical change to how the existing FETs are used.

Or just buy an ESC that ships in reversible configuration.

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