ESP8266 Community Forum

- Tue Apr 12, 2022 9:12 pm #94262 lm393 comparator, 5V power supply, I want to make a voltage comparator with a gate threshold of 3.9V, why is the output always 0
The inverting input is 3.9V, no matter how much the non-inverting input is, the output is 0,; when the inverting input is 3.5, the output is 5V, is the common mode voltage input too large?
Introduction to LM393 comparator: https://www.utmel.com/components/lm393n-comparators-ic-application-pinout-and-datasheet?id=109

- Thu Apr 14, 2022 7:23 am #94289 In Non inverting mode
When Vin>Vref; VOUT=HIGH
when Vin<Vref;VOUT=LOW

In inverting mode
When Vin>Vref;VOUT=LOW
when Vin<Vref;VOUT=HIGH

From your description, it looks like your IC is working alright in inverting mode. But in Non-inverting mode, it is not performing the way it should. I request you to check your comparator circuit again. Kindly check all the connection points and power supply. Check other components(Like resisor) that are connected to the LM393 is of the right value. If you cannot find any problem, perhaps you IC is bad.