Light Comparator (MIN206E)

With this circuit it is possible to compare the ink tones, the intensity of light sources or even of degrees of illumination. The circuit consists of a bridge using two LDRs as sensors. When the light intensities in the LDRs equals to the bridge it balances with the null indication in the instrument, a microammeter with zero at the center of the scale.

The circuit can also be used with a comparison scale in the potentiometer. The power can be made with voltages of 3 or 6 V obtained from ordinary batteries of any size. In Figure 1, we have the complete diagram of the comparator.

Figure 1 - Full diagram of the light comparator | Clique na imagem para ampliar |

The circuit can be mounted on a terminal strip, as shown in Figure 2.

Figure 2 - Assembly based on a bridge of terminals

Material list

R1, R2 - 1k ohms x 1/8 W - resistors - brown, black, red

R3 - 4k7 ohms x 1/8 W - resistor - yellow, violet, red

P1- 10 k ohms - potentiometer

LDR1, LDR2 - Common round LDRs

S1 - Single switch

M1 - 200-0-200 uA 0or 50-0-50 uA - microammeter with zero at the center of the scale

B1 - 3 V or 6 V - 2 or 4 batteries of any size

Miscellaneous: battery holder, terminal strip, mounting box, knob for the potentiometer, wires, welding, etc.