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Topic: Need a powerful multiplexer... (Read 1 time) previous topic - next topic

deadbird

Hi everyone.
I was thinking about a nice project that would be interesting to develop: a LED clock. Here's how I imagine it (roughly):


I was wondering if there's a multiplexer huge enough to handle, let's say:
- 1 LED / second = 60 LEDs
- 2 extra LEDs / 5 minutes mark = 24 LEDs
- 4 digits, 9 LEDs high * 5 LEDs width = 27 LEDs
- 1 comma = 2 LEDs
Total: roughly 110 LEDs...
So I need a 7bits multiplexer? a 128++ pins monster? Does it exist?

Nate

I would highly recommend using shift registers. The data rate is going to be very slow, one change per second, and the logic of a shift register is VERY easy with something that is set sequentially like this.

deadbird


James C4S

Look into the TLC5940.  It is essentially a shift-register with built-in LED drivers.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

UltraMagnus

you could also use normal registers, 74*374, etc.  They need more pins (although this can be reduced using a decoder for the address lines) but are far faster than serial shift registers.

deadbird

Wow, I just took a look a the TLC's datasheet, I think this baby's just took complicated for me! But I haven't mentioned that I just have figured out how to handle a SN754410 and didn't succeeded with 74HC4051 ;)

James C4S

Quote
Wow, I just took a look a the TLC's datasheet, I think this baby's just took complicated for me!


With the Arduino library, it is much easier to use than rolling your own solution.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

DhanMorganSolar

You can use several 32 bit ADG731 mux, very easy to interface and you can cascade however many you want.


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