Friday, 15 November 2019

integrated circuit - LM339 Comparator IC is not responding to any input


I came into Electronics through Arduino, so pardon me if my knowledge about non-Arduino circuits is somewhat silly. I am preparing a small electronics project for my school with LDRs to detect light levels. With, an Arduino I could easily detect light levels and when they go down a threshold, I turn on a relay.


But, I wanted to make this without an Arduino, so I though of using an LM339 Comparator. I connected pin 3 of IC to Vcc and pin 12 to Ground. Pin 4 has an input lower than the input on pin 5 which receives input from Vcc. Lastly, I had the output 1 from pin 2 connected to an LED.


This circuit is only to test the comparator. If it works I am going to change the reference voltage and in place of the LED place a transistor. Here is a quick circuit Diagram I created:enter image description here


But, the LED does not glow. Even if I switch the inupts, the LED does not glow. I tested this in circuits.io, the online simulator. It works perfect there. But, the problem persists on the breadboard.


How do I get the LED to glow in my circuit on the bench?


UPDATE: I just got the LED glowing with the help of Raj, but how can I connect the base of a transistor in place of the LED.




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