This simple circuit controls the brightness of an LED from LDRs, NTCs, PTCs or other resistive sensors. The difference from the previous one is in the action of the sensor. The adjustment potentiometer P1 can have values between 10k and 100k according to the nominal resistance of the sensor, and the transistor may be the BC548. The resistor in series with the LED determines its brightness. The voltage can be between 6 and 12 V.
