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bi-directional motor control using two mosfets

bi-directional motor control using two mosfets

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I am trying to understand how a dual motor controller works. It drives two DC motors with support for running the motors in the opposite direction, as well as stopping them. Looking at the board I spotted two FDS4953 Dual P-Channel mosfets, presumably one for each motor, as well as a transistor. Their schematic shows that each is comprised of two mosfets. How is the board able to achive this with just two mosfets per motor?mosfetdc-motormotor-controllershareedit  follow  flag asked 7 hours agoDionysis Spinellis1111 bronze badge New contributor

  • 1you linked the driver datasheet instead of the module schematic – jsotola 6 hours ago 
  • 1it may be a case of false advertising … the module can drive two motors unidirectionally or it can drive one motor bidirectionally if you make connections only at the terminal blocks on the module … off-board connections would be required for bidirectional control of two motors – jsotola 6 hours ago 
  • 1@jsoola:: I don’t have the circuit schematic; that’s why I asked the question. – Dionysis Spinellis 4 hours ago
  • 1@jsotola: Regarding your second comment, an example program on the maker’s site microbot.it/sketches/Dual_DC_Motor_Driver_4A_V3_test_sketch.ino shows simultaneous control of both motors using two potentiometers (this was also useful as i was not sure whether i could drive the motor using a pwm signal). – Dionysis Spinellis 4 hours ago
  • 1“Looking at the board I spotted two FDS4953 Dual P-Channel mosfets” – evidence? – Bruce Abbott 4 hours ago

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How is the board able to achive this with just two mosfets per motor?

Right on the front page is the hint to how it does this: –

The Dual DC Motor Driver 4A V3 allows to indipendently drive two DC motors, controlling both velocity and direction. The minimum supply voltage allowed is 7V, so you can use also two-cell LiPo batteries (7.4V) that grant small dimensions and low weight characteristics.

Ignoring the spelling (I’m certainly no expert), it suggests using two 7.4 volt batteries and this means that the motor can “return” to the midpoint and one MOSFET will pull the motor up to 14.8 volts (applying +7.4 volts) to get forward motion whilst the other MOSFET can pull it down to 0 volts (applying -7.4 volts) to get reverse direction.shareedit  follow  flag answered 7 hours agoAndy aka298k1717 gold badges231231 silver badges523523 bronze badges

  • 1Thank you! I think the reference to the two cell 7.4 volts means two 3.7 LiPo cells connected in series to drive the board, rather than center tapping two 7.4 batteries. Also the board’s input power terminal provides only two screw inputs, rather than three. – Dionysis Spinellis 4 hours ago
  • 1@DionysisSpinellis Yes I got the voltage stated incorrectly but my point is still valid. At the series junction of the two batteries is where one wire on the motor makes a connection. The other connection on the motor connects to the half bridge output hence, the motor can be driven forwards, backwards or anywhere in between. Do you follow? – Andy aka 4 hours ago
  • I don’t follow. I think something goes wrong somewhere. – tlfong01 25 mins ago   

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