Simple Automatic Brightness Control Circuit

Automatic Brightness Control is the automatic adjustment of the exposure factors such as mA and V. ABC is used to keep the brightness of the display or bulb at a constant level. It involves the adjustment of the V and mA automatically depending on the part of the anatomy being examined. This can be achieved using a LDR, for instance, which monitors the ambient light and change its resistance this resistance changing use to adjust the V, the mA (or both) accordingly.

Automatic Brightness Control Circuit

This simple auto brightness adjusting circuit composed with a LDR. The LDR connected with the Base pin of the PNP transistor. By the LDR feature that its resistance changes with the ambient light, the voltage of Base change. When the ambient light is bright, the resistance of LDR is low, and the voltage of Base is reducing and the ambient light is low, the resistance of LDR is high, and the voltage of Base is rising. Then the output voltage of transistor is changing. The variable resistor is use to adjust the sensitivity of circuit. Supply voltage for this circuit is 12v.

Light Dependent Resistors (LDR)

A Light Dependent Resistor (LDR) is a resistor that changes in value according to the light falling on it. An LDR commonly has a high resistance in the dark, and a low resistance in the light.

ABC Circuit