Transistor light meter circuit diagram

When the solar cell is exposed to light, the voltage generated causes VT6 to turn on. The degree of conduction of VT6 is directly proportional to the intensity of light. The conduction current of VT6 produces a voltage drop on R1, and the bases of VT1~VT5 obtain a forward voltage . However, due to the different size of the signal and the voltage reduction effect of VD1~VD4 (0.6V), the bases of VT1~VT5 will receive a positive voltage. The forward voltage decreases one by one, so TV1~VT5 are in different working states, so some of VD5~VD9 are bright and some are dark, indicating the strength of the signal level , that is, the intensity of the light.