I am building an electronic pendulum. I want to use a 2N2222 to power the drive coil when the pendulum bob interrupts an IR beam. The pendulum bob is magnetic and moves in reaction to the drive coil. I am trying to modify this circuit as follows
The 100 ohm, the 1K ohm, and the red led will be removed and an air core coil will be substituted. The coil consists of a plastic sewing machine bobbin fully wound with 30 gauge magnetic wire. Resistance 10 ohms, inductance unknown. The coil is bridged using an led to suppress the back EMF caused by the collapsing field.
The circuit as shown works BACKWARDS. The 2N2222 turns on when the photodiode is illuminated and turns off when the photodiode is not illuminaed.
For simplicity the source of the ir beam is not shown.
How can I change the circuit to make the 2N2222 turn on when the ir beam is interrupted and off when the off when the beam is not interrupted.