- An IR circuit consists of an IR Emitter (an LED) and an IR Detector (a BJT)
- Sizing a resistor for the IR Emitter is just like an LED, figure out the forward voltage drop, then use half the max continuous current spec
- If the detector is being hit with IR light the signal will be low.
- If the detector is in darkness the signal will be high.
- The detector circuit is similar to a basic switch circuit in that the signal line is held high via a resistor then the sensor can bring the signal line low.