How man shift registers can be connected?

Forum 2005-2010 (read only) Hardware Interfacing
1

i am working on a project with 8x32 led display with 32 shift registers (no multiplexing) in serie.

when i shiftout 32 bytes i have no problem, but in scrolling text i see some problem in the last 8-9 shift registrers (some leds that dont need to flash they flickering with no reason ), i had no problem when i tested in 8x16 display,

is it because i am using too many shift registers?

i tried to see if i have problem in my code but i couldnt find any,

and something else, do i need to put a capacitor? i saw somewhere, does this have to do with my problem?

2

A capacitor could help. I've heard that sometimes the latch pin can flicker without one.

3

You should put a capacitor across the power rail of each shift register:-
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

However you should not put a capacitor on any of the logic lines. Yes there is a popular web page that shows this but it is wrong and could end up damaging your arduino.

4

Sorry, I was wrong (and a little unclear).
Turns out that IRS the arduino website tutorial page that mislead me.

This should probably get fixed sometime.

5

Problem is that this is not an editable Wiki like the playground stuff.

6

Well someone, I dunno who, is able to edit things on it.

7

Ok I have sent a PM to one of the site administrators asking who can edit it.