enter image description hereI have this motor driver design set up on a breadboard for a bipolar stepper motor. I was able to drive the motor forwards and backwards for about 5 minutes. I realized that two of the P mosfets were getting hot until they became untouchable. Then I turned off the power supply which was limited to 6V, 0.8A. Then I turned off the power supply until the mosfets were cold. I turned the supply on again but I didn't send any commands to the motor driver and I realized that the same mosfets were getting hot again. I tried to move the motor forwards or backwards but it would only stall. I would appreciate if someone could help me troubleshoot the design of the motor driver. The mosfets I am using are 2N7000, IRZ44N and 4P03L04

The motor I am using is this one https://www.amazon.com/gp/product/B00PNEQKC0/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1 Nema 17 Rated current 2.0A & resistance 1.4ohm

The GPIO logic level from my mcu is 3.3V. I am not suppose to use motor driver ics since it's for a school project, but I'll appreciate any other suggestions, thanks.

  • \$\begingroup\$ also the frequency I used for this motor was between 50Hz to 220Hz, using full step mode. \$\endgroup\$ – pekoms Mar 26 at 5:20
  • \$\begingroup\$ Do you not see a problem with 6V/1.4ohm= 4.2A current limiting then dropping Voltage so RdsOn rises and heats up? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Mar 26 at 6:11
  • \$\begingroup\$ You should show on diagram what voltage Vcc is and what voltage drive levs are. || VERY IMPORTANT - you do not anywhere say what your drive levels are in various modes. You say "but didn't send any commands to the motor"-> in that stationary state what are the drive levels? IF all FETS were off then no heating should occur. BUT if the stepper has voltage across a coil or two coils then, as SSG75 says, you get large currentv through large Rdson FETS = heating. | Please advise drive levels in each state. \$\endgroup\$ – Russell McMahon Mar 26 at 7:26
  • \$\begingroup\$ hi rusell, vcc is just connected to a dc power supply (rigol DP711). I limited the voltage to 6v and the current to 0.8A. My voltage levers are these: \$\endgroup\$ – pekoms Mar 26 at 10:44
  • \$\begingroup\$ My driver levels are these: to stop 0000, for forwards 0101, 0110, 1010, 1001. where the most left bit is CON4 and the most Right bit is CON0. for backwards, 1001, 1010,0110, 0101. \$\endgroup\$ – pekoms Mar 26 at 10:56

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