VOM Light Meter

This circuit detects the amount of light that is shining on the phototransistor Q1. As the light intensity increases at the input of Q1 the voltage output gets amplified by the 741 op amp IC1. You can typically purchase a analog meter movement unit from Radio Shack still and alot of surplus mail order companies.

From : http://home.maine.rr.com/randylinscott/oct21.htm

Electronic projects circuits