Phototransistors are a new tool for me, and I'm wondering how to select one that will match a specified source (LED worklight, color temp 5000K, wavelength unspecified). My prototype works but apparently does not match the light source. Of course the data sheet for the transistor (ROHM RPM075PTT86) specifies its spectral response. I can't find out how to correlate a color temp of 5000K to a wavelength. There must be a better way than trial and error. For reference the app is a conveyor package detector, light is overhead strip about 2' above the surface, sensors are in a strip across the conveyor. Any suggestions appreciated!
Harry
Datasheet HERE
Best Answer
Your photo transistor is optimally responding to 600 nm.
White leds of 5000k tend to have their heighest peak in the blue range of 450 nm and a lower hump over 525 to 550 nm.
The setup is not ideal, but should still have some reasonable response, as long as you properly aim them at the light source. Both the transistor and the light source spectrum peaks are curves, and should work even if not directly matched, as long as the output is in the curve. Without knowing your specific lights spectral range, we cannot give you better guidance.