I need to build a light sensing circuit for a class project.
I need to build a light sensing circuit for a class project. I have already built one circuit using a 741 opAmp chip, a 1 meg ohm photo cell, a 1 meg trimmer, a 1k, 100k, and a 47 ohm resister, and a 2n2222 transistor as well as a 12vdc relay. The circuit senses the light and the sensitivity can be adjusted by the potentiometer. It works great for tuning it in to need a certain amount of light intensity to trigger the relay. The problem is i need to be able to put limiting factors on it. I need to be able to set it to turn the relay on if a certain intensity is reached, but not turn on if the intensity gets to great. Is there anyone who can help me with the schematics on how to achieve this?