I want to control a 1.5V motor using a microcontroller output. The motor draws about 450mA stall current. I am considering to use a Darlington transistor such as TIP120 to bridge the microcontroller output and the motor. However, the Darlington transistor will introduce a rather high collector-emiter saturation voltage of about 0.6V at Ic=400mA. This will mean the motor will be operated at about (1.5V-0.6V)=0.9V only. Will the motor spin with 0.9V only? And even if it spins, will it produce significantly lower torque?

If using a Darlington transistor is not the way to go, what are my other choices?

Due to space constraint, I still prefer to have the motor powered using one 1.5V battery only. So, adding another 1.5V battery may not be preferred in my case.

  • \$\begingroup\$ What is the Vcc of the uC ? (operating voltage) \$\endgroup\$ – Triak Feb 1 '15 at 14:03
  • \$\begingroup\$ The Vcc of the microcontroller is 5V. The microcontroller will be powered using a power source different from the motor power source. \$\endgroup\$ – Rully Feb 1 '15 at 14:05
  • \$\begingroup\$ Try using mosfets \$\endgroup\$ – Triak Feb 1 '15 at 14:12

Use a MOSFET with low Rds instead of the Darlington.

eg. 0.1 Ohm Rds would cause a voltage drop of 45mV.


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