Electronic – Are photoresistors reliable for light sensing applications

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I've used photoresistors for hobby projects before, such as this one:

http://www.foxytronics.com/learn/electronics/kit-guides/starter-electronics-kit-guide/making-an-led-light-sensor

However, now I'm working on a commercial product that needs to sense when it's dark and I'm unsure of whether the circuit I designed on the above page is adequate. The reason I'm concerned is that in my experience photoresistors have very low wide tolerances (i.e. high deviations in photosensitivity).

If you were designing a low cost circuit that could output a HIGH logic level when dark and LOW logic level when light (or vice-versa), would you use a circuit with a photoresistor like the one I designed, or is there something else that is more reliable?

Best Answer

How to deal with highly variable components? Pick one or more:

  1. tune each device manually
  2. restrict your problem domain to fit within the available tolerance of the components
  3. tune each device automatically (e.g. a circuit built into your device which finds the light-dark range of the photoresistor automatically and saves the result somewhere)
  4. sort devices to fit your problem domain

The best results will happen when you hit the sweet spot of the device working correctly for all inputs with a minimum of labor and parts.

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