Help with photoresistor idea

[mozly]

Hello,

So I have this idea for a little project but I'm having a problem. So what I want to do is a gizmo that points towards the brightest spot in a room, think of it as a sunflower. I'm not surehow to go about doing this; furtheremore, I don't want to use a microprocessor, ICs only. let me explain.

I was thinking of having a photoresistor attached to a motor so it spins around the room once to find the least resistance then spins again and sits there. The problem is if I move the sunflower to another room I'd need it to be able to spin and realize it has moved.

Another idea is that I arbitrarily set a certain resistance value and have the sunflower turn till it finds that value in the room. The problem with that is if it finds a bright spot that is not the brightest spot.

I am open to any open-ended idea and specifics are welcome too.

thanks in advance.

 

[Grossel]

Why do you want the motor to rotate an extra turn?

You could use a derivator (opamp with resistor ad cap) as input from the ldr. In the exact moment where the input voltage goes from being lighter to getting darker (voltage vill follow) then the output from the derivator will change polarity. Now the motor can stop.

 

[PCBWING]

I made something similar in childhood. The circuit in my bookcase somewhere. Tomorrow I will find.

 

[MikeMl]

Read this thread.

 

[mozly]

wow thx for the input