I have an idea for a project and am looking for a laser sensor. The laser is a red visible dot. In an ideal world the sensor would be just like a photo cell. When the laser hits the sensor it sends a signal to the UNO saying that a signal was received.
Use a phototransistor. Light acts like base current and causes the PT to conduct (ok, amplify the larger base current). Figure 9 in this ap note (http://physlab.lums.edu.pk/images/1/10/ … ircuit.pdf) is what you want. Choose a resistor value in the range 10K or so. In the pull up case, no light reads as a digital 1, light reads as a 0.
Note that your detector will respond to any light in the right spectral range so you might want to go to a more sophisticated approach where you modulate the laser beam. Look for the modulated pattern to make sure the signal is from your laser. For example, 1Khz pulses are easy to detect - count at least 3 or 4 before deciding it’s real. You can get pretty sophisticated - look into IR receivers for remote control for higher security needs.
Though, if you are doing a simple beam break application - you could just use a shroud to prevent light from other angles. It’s simple and probably would work pretty well.
Thanks Philba, That puts me on the right track.
Does the PT have a range say 1-10 and the UNO code says to exclude 1-8 so it only reads the intense light from the laser beam?
It’s not that simple. The digital reading from the PT is dependent on the PT itself, the pull-up resistor value and what the AVR interprets as 1 or 0. You could use an analog input and look for the threshold yourself. If you do that, build in some hysteresis (look it up in wikipedia, hysteresis in engineering section) to your detection code.
You could also play with the pull up resistor value to change the point at which the digital input value goes from 1 to 0.