I am working on a control circuit to run a 12 volt DC motor. The circuit uses a 555 timer to turn the motor on and off based on input from a sensor. The output from the 555 goes to a motor driver (IXF007T half bridge driver) which runs the motor until the 555 output goes low. I would like to be able to manually run the motor with a switch that can turn the motor on and off independent of the 555. I have the +12 volts from the switch connecting between the 555 output pin 3 and the driver input pin 2. I placed a diode between the 555 and the switch connection point to prevent any current from running back to the 555 when I switch on the motor.
When I run the motor manually with this circuit everything works fine for a period of time (2 or 3 minutes) until the motor wont shut off when I release the switch. It appears that the 555 output goes high and that keeps the motor running until I reset the 555. I can only conclude that some current is flowing through the diode to the 555 pin 3 and this is causing the 555 to go high when the motor is being run manually.
I wonder if there is something I am doing wrong here. When the manual switch is not included in the circuit everything works fine.
When I run the motor manually with this circuit everything works fine for a period of time (2 or 3 minutes) until the motor wont shut off when I release the switch. It appears that the 555 output goes high and that keeps the motor running until I reset the 555. I can only conclude that some current is flowing through the diode to the 555 pin 3 and this is causing the 555 to go high when the motor is being run manually.
I wonder if there is something I am doing wrong here. When the manual switch is not included in the circuit everything works fine.
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