Hello,
I've attached my circuit that shows a simple schematic of a motor control circuit.
I am using a PIC processor to supply Pin-3 either ground or 5 volts (Logic 0 or 1)
to control the motor via a 2N2222A NPN transistor. The motor is 3vdc and pulls about
50mA. I've placed a diode in series to drop the voltage a bit. All in all (correct me if I'm wrong),
the transistor and diode in series drops the voltage down close to the 3vdc requirement of the
motor. (5-.7-.7)= 3.6vdc. I've got a snub diode to remove any negative swings from the
motor.
This motor energizes when a positive value is placed on the base of the transistor and turns off
when the base is ground as designed. But it always fails. I have replaced all circuit components
with no results. The transistor is not shorted. The transistor can switch up to 800mA.
Here is the failure:
The voltage on the collector of the transistor goes up from 5vdc to 6-7 vdc. It does not matter if
the base of the transistor is high or low. At times there is a square wave
on the collector that slows the motor down - this square wave is not coming from the Processor (base of transistor).
Am I missing something here - It seems like a very simple circuit? Do I have the wrong transistor?
Thanks for your time - any suggestions would be helpful.
George
I've attached my circuit that shows a simple schematic of a motor control circuit.
I am using a PIC processor to supply Pin-3 either ground or 5 volts (Logic 0 or 1)
to control the motor via a 2N2222A NPN transistor. The motor is 3vdc and pulls about
50mA. I've placed a diode in series to drop the voltage a bit. All in all (correct me if I'm wrong),
the transistor and diode in series drops the voltage down close to the 3vdc requirement of the
motor. (5-.7-.7)= 3.6vdc. I've got a snub diode to remove any negative swings from the
motor.
This motor energizes when a positive value is placed on the base of the transistor and turns off
when the base is ground as designed. But it always fails. I have replaced all circuit components
with no results. The transistor is not shorted. The transistor can switch up to 800mA.
Here is the failure:
The voltage on the collector of the transistor goes up from 5vdc to 6-7 vdc. It does not matter if
the base of the transistor is high or low. At times there is a square wave
on the collector that slows the motor down - this square wave is not coming from the Processor (base of transistor).
Am I missing something here - It seems like a very simple circuit? Do I have the wrong transistor?
Thanks for your time - any suggestions would be helpful.
George
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