Need a powerful multiplexer...

Forum 2005-2010 (read only) Hardware Development
1

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?
2

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.

3

Could you develop a bit ?

4

Look into the TLC5940. It is essentially a shift-register with built-in LED drivers.

5

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.

6

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 :wink:

7

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.

8

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