Daisy chaining multiple large 7 digit drivers

Components & Accessories Displays
1

Hi,

I am using 9 large (10 inches) seven segment display in my project which I am driving using ESP32.

Unfortunately I am having trouble with digit 7,8 & 9. The segments from these 3 digits which are supposed to be OFF aren’t completely off sometimes. When I have digit 1 - 6 displaying numbers which need lesser segments ON, digit 7-9 works fine (the segments which are meant to be OFF will be OFF). But when I, for example, display number 8 for digits 1-6, I see the problem with digits 7-9.

When I measure the voltage b/w the segment (& 12V pin)) when having trouble I see it ranging from 0v (when working correctly) to various voltages like ~3V, ~6V.

I don’t have electronics background and relying on online materials for my project.

Thanks in advance for your time

Cheers

2

Hi RamP.

It sounds like the digits at the end of your chain are not getting enough voltage to work properly. What you’re going to want to try is to run an additional 12 volt and ground wire from the first driver all the way down to the last driver. That will supply power to both ends of the chain and then both ends should see roughly the same voltage.

Why does this happen? There’s a small voltage drop from board to board due to resistance in the traces in the board and your wiring down the chain and by tying both ends of the chain together electrically, you decrease the resistance and voltage drop.