I bought some laser diodes on ebay recently that were advertised as 5mw which look like the image shown:
To comply with law, I hooked it up to a 9V battery with a 22K resistor.
I made a simple detector as follows with an LM324 op-amp
I connected inverting input to output via 4.7M resistor. Output is connected to cathode of LED via 1K resistor. Non-inverting input is pulled up by 1M resistor and pulled down by the 3mm clear lens photo-diode detector connected in reverse.
The detector works nice if the laser beam shines right at it (which is what I want), but I find that with such a low wattage, I have to be super-precise at shining the beam directly at the detector to get it to respond. If I'm off by even 1mm, the detector won't respond.
I have read about special kind of glass (or something?) that is supposed to scatter laser beam light when hit? but I'm not 100% sure what it is called or if it commonly exists. Can someone shed some light on this? Basically I want my detector to respond if it is in a transparent case and any part of the transparent case that the component side of the circuit is facing is hit with a laser beam.
Can anyone suggest what I should do? and raising power is not an option since laws prohibit lasers more powerful than 5mw.