I am working on a pendulum driven by light (actually an IR Diode) reflected off a reflective surface.
The pendulum bob is a shiny neodymium magnet.
As the pendulum bob reaches it’s lowest point the transistor will turn. I expect to use a small coil with appropriate protection against voltage spikes to drive the pendulum

I am trying to design a circuit similar to the dark detecting circuit shown at the following url :
https://www.evilmadscientist.com/2007/a-simple-and-cheap-dark-detecting-led-circuit/

The led will be replaced with a coil of approximatly ohms dc resistance.
Could I modify this circuit so it will switch the led (actually the coil) ON when it detects actually IR.
Would like to keep supply voltage down to 3 volts is possible.
I hope my thinking is not too simplistic