I'm playing around with the examples on the internet of using a toy laser pointer and photo resistor to make a trip wire. Everything works fine. My question or problem is that I want to have maybe 30 trip wires controlled by an Arduino, but each trip wire requires an analog input. All the Arduinos that I find don't have that many inputs.
Is there a way I can use a digital input for the trip wire. To give me a high 5v or low 0volts signal. I've used a pot in series with the photoresistor in stead of a 10k resistor. To see if I can adjust the threashold of the voltage drop to give a low or high digital signal.
I don't know if I'm doing something wrong or if its possible to use a digital input. I don't care if I use a analog or digital input, but most of the Arduinos have more digital inputs to use for my project.
I would think you would use a pot in series with the photo resistor instead of a set resistor, so I can calibrate the trip wire. Without adjusting the arduino sketch for different lighting conditions.
Can't you use a photo transistor instead of a photo resistor? Than it will be a digital on/off signal instead. Than you can use any number of shift registers, or I2C multiplexers. Or I think there is an analogue I2C multiplexer but I can't remember the number off hand. Check the Playground I think it is mentioned there, it's like a PCF 9535 or something.