I need to detect the state of an LED in a machine that I cannot connect to in any electrical way. So I would like to measure the light emitted from this LED.
- The ambient lighting is low to very low (both the machine containing the LED and the sensing device are inside a box with few and small holes)
- The sensing component can be very close and well aimed at the LED (distance between 0 and max 5mm)
- The LED is orange (if that is relevant?)
- Input will be processed by a PLC
My question is: what component meets the following criteria the most? Criteria in order of priority (from high to low): reliable detection, simple wiring (few components, easy to wire to let's say an arduino), easy programming the microcontroller, and low price.
I am looking into these alternatives (but maybe there are more?).
- LDR (light dependant resistor)
- Phototransistor / photodiode
- LED as a light sensor (in the same colour as the emitting LED)
Which component meets the criteria the best?