light sensing motor sensor

Have been thinking about a way to get a motor to move according to light conditions around it. I know there are simple ways to do it already, but the idea here is to get as few and simple parts as possible at the prize of battery life. The idea is that two photoresistors decide which way the motor turns, depending on which photoresistor is in the brightest light.
here's two diagrams done i MSPaint:
**broken link removed**

I have doubts about this second one..
**broken link removed**

I suspect that both these circuits will use batteries at a furious rate, but that is not an issue.

No, they won't use batteries at a furious rate, because they won't work at all, LDR's are far too high a resistance.

The resistance depends on the amount of light, but are you suggesting that the variations are only a couple of %'s of the total resistance in a LDR`?

I thought you could get them in different values.. Am I wrong on that one as well?

maneuver said:

The resistance depends on the amount of light, but are you suggesting that the variations are only a couple of %'s of the total resistance in a LDR`?

I thought you could get them in different values.. Am I wrong on that one as well?

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You can get them in different values, but none anywhere near low enough to drive a motor.

LDRs

Could you not parallel a few LDRs to get the resistance down low enough to run the motor? Depending on battery size and motor requirment of course.

willy1usa said:

Could you not parallel a few LDRs to get the resistance down low enough to run the motor? Depending on battery size and motor requirment of course.

Click to expand...

I suggest you try looking what values are commonly available, and what figure your 'few' might consist of

You might look at how light sensors are used in control motors in robots and see if you can adapt their method. There are several websites that talk about making robots and may have some tips.