I am digital electronics noob and it's been a long time since I've even tinkered with this stuff. I am trying to design/build a simple circuit to test a software application I am developing. I have a 12v solenoid that I want to fire/push when I light up a certain area of the monitor.
I was hoping to use a photoresistor which I can tape to the monitor. I have an assortment of 5 but the one I was trying to use has a resistance of 800 ohms when the monitor is lit and 12k ohms when the monitor is dark.
Can anybody suggest some approaches or even better design a simple circuit that I could use to do what I described.
Summary of current parts, I can purchase additional ones if needed:
12V/3A power supply CdS Photoresistor (800 in light, 12k in dark) NPN transistors 741 Opamp chip 12V solenoid (30Watt power rating)