Can LED strips be used as photodetectors?
An single LED, or multiple LEDs connected in series can be used as a photodetector. The output needs to be suitably amplified.
However, a commercial LED strip cannot (usually) be used as a photodetector (without modification) because a commerical LED strip generally contains other components which will interfere with such use. The same applies to devices get commonly called &quot;LEDs&quot; which are more than a single light emitting diode. If they contain extra circuitry, their use as a photodetector will probably be problematic.
One way to tell if something called an LED is simply a light emitting diode, or whether it contains extra circuitry, is whether it requires an external resistor to prevent over current, when attached to a voltage source. That is, if you can directly connect the device to, say a 5V source, then it is NOT simply an LED, even if it is advertised as such. Similarly, if you can connect a strip to some voltage source, without a current limit resistor, it is probably not suitable.
If you have a high impedance volt-meter, you can always test your LED or LED strip, by shining light at the LEDs (unplugged of course) and seeing if you can measure any voltage across the terminals. If you read a voltage, then you can conclude that you can use it for a photo-detector. However, if you don't read a voltage, and your meter can be set to read micro-amps, try that. However, even if you cannot get a reading either way, that doesn't completely rule out the possibility of using the LED as a photo-detector. As I said, the output of a LED used as a photo-detector needs to be amplified.