LM324 Comaprator with leds, slow glow effect

Thread Starter


Joined Feb 8, 2023

I've made a custom pcb using comaprator circuit LM324.

The purpose with this circuit is to create a led-bar 1-10 with leds ...

The issue is that when the leds shifts from one level to another, it has a tendence to flicker, becuase of the digital on/off from the comparators.

What I would need is a delay/glow effect on the leds, so that the leds take f.example 1s to turn on/off, or something similar.

1. Limited space
2. 0603 components

Any suggestions?



Joined Jun 22, 2012
That's because there's no hysteresis on the op amps, you're better off using a LM3914.

For delay you need to put capacitors on the inputs .


Joined Aug 21, 2008
Hysteresis is obtained by adding a little positive feedback to the input of the comparator .
Google says "A small change to the comparator circuit can be used to add hysteresis. Hysteresis uses two different threshold voltages to avoid the multiple transitions introduced in the previous circuit. The input signal must exceed the upper threshold (VH) to transition low or below the lower threshold (VL) to transition high."


The LM324 is not a comparator - it is an opamp. The are interchangeable to an extent, but opamps are pretty good for analog signals but they are slow and comparators such as the one mentioned by @Dodgydave in posts #2 will switch much faster and decisively (to use a technical term).