LM393 voltage comparator works

How does LM393 work in this circuit?

R-Light is the photodiode, the VCC of LED light is 6V.

LM393 voltage comparator, will be connected to the R-Light end of the photodiode receives light when the resistance changes into a voltage signal transmitted to the voltage comparator's non-inverting input INB +, the change of the voltage signal and the voltage comparator in the opposite phase Input terminal INA-side of the reference voltage compared to when the non-inverting terminal INB + voltage is greater than the inverting terminal INA-terminal voltage, the voltage comparator output OUT output high voltage, when the non-inverting terminal INB + voltage is less than the inverting terminal INA- Voltage, voltage comparator output OUT output low voltage, Light LED light at this time.

In the absence of illumination, the photodiode has a large resistance, and the voltage at the voltage dividing point formed by the resistor R23 and the photodiode rises so that the voltage at the non-inverting terminal INB + is greater than the voltage at the inverting terminal INA-, and the voltage comparator's output OUT High voltage, Light LED is not bright at this moment. When there is light, the resistance of the photodiode is very small, and the voltage of the voltage divider formed by the resistor R23 and the photodiode drops so that the voltage of the non-inverting terminal INB + is smaller than the voltage of the inverting terminal INB-, and the voltage comparator output OUT is low Level voltage, Light LED lights.

Potentiometer VR2 connected to the inverting terminal INA- is used to regulate the voltage of the terminal. This voltage is the threshold voltage of the voltage comparator input for lighting sensitivity adjustment.

Relevant LM393 series products

Author：Brittany Antonia （The author of article owns the copyright.）