I need to output to 20 x 7-segment displays for displaying sensor outputs, using various sensors and modules. I was planning to use a cd4511 chip and transister to multiplex, such as in the attached picture.
My question is- how many displays can the 4511 handle? Can the one chip do it all, or does the rule of 8s also apply in this case?
Thanks in advance for any replies.
Rob.
how many displays can the 4511 handle?
I don't think there's any practical limit because it only drives one at a time.
does the rule of 8s also apply in this case?
What's the rule of 8s?
Where I think you will have trouble is that the duty cycle will only be 1 in 20, the displays might be quite dim.
There are chips designed to do this, the largest I can think of does 8 displays (MAX7219/MAX7221) but you can daisy-chain them (actually you can't daisy-chain those MAX chips but some you can IIRC, I just can't find one now :)).
EDIT: The AS1118 can drive 64 segments (8 digits with DP) and is daisy-chainable.
Rob
Thanks rob.
It gives me a start.
If I'm not restricted by the 8 digits, I might try using 2x 4511 chips giving a duty cycle / by10.
Had a quick look at the as1118 and am about I have a stroke trying to work that one out.
Thanks again.
Rob.
