Quote Originally Posted by Freman View Post
Which of these would you use?
* Phototransistor (Say: http://tinyurl.com/5bspbk for example)
* Photodiode (Say: http://tinyurl.com/58wuwp for example)
* or a full on IR Receiver (Like: http://tinyurl.com/54vqs6) and PWM the IR led(s) to the right frequency.
Can't really say for sure. Phototransistor/diode would probably require a bit of 'lensing' to aim to light right, but you wouldn't need to be really accurate or anything. But...you might trip the sensor with the ambient light in the room, so you'd need to throw a bit of 'fuzzy logic' in the program, maybe a counter that say counts 10 times in a row it senses the light and kicks out whatever it is you want to kick out.
An IR TX/RX may have it's advantages...relatively easy to do, one obvious one being that you'd only be looking for the signal that you're sending out, fewer false triggers.
Either way you go, if you know when the IR is on, then you can sense if the IR is really being reflected vs. with ambient light, if you know the IR is off, and you're sensing the signal, then you know the room light is getting in the way.