Hey there, I think you're using only the 74HC595 connected directly to the LEDs? No current limiting resistors at all? The more LEDs are on, the more current will flow through the 74HC595 which is limited to about 35mA for all pins together, while a single red LED will source 20mA at 2.1V (you're using 5V). 35mA for 8pins means you have about 4mA for a LED and would need 680ohms per LED. But 4mA would barely make them glow. With any luck you can use 330ohms and get it to work at 10mA per LED, but you would work out of the max values from the datasheet. Hope I could help someone.

@alyology0

5 жыл бұрын

35mA for each pin* according to MAXIMUM RATINGS table in page 2 of the datasheet

@someguy4915

4 жыл бұрын

@@alyology0 35mA MAXIMUM per pin, you should never run 35mA in normal operation and a 70mA MAXIMUM total for all 8 pins, again you should never run 70mA under normal operation... With 70mA total you can light up 8 LEDs at ~7mA each to total 56mA and stay well safe within the maximum rating of 70mA so you don't burn the IC out. The 74HC595 really does not appear to have been designed to directly drive LEDs anyway.

Adding register is right, But if IC has problem then you should remove led from 15th pin of That IC