Driving 26 7-seg LED displays with ATmega328

I am well aware, that I'd need a multiplexer for that, but still - is it capable to do it with a single ATmega328? Will I have to multiplex the multiplexers?
I'd be using small, like 12mm high displays.

I'd like to show on a single board:

-Date (8 displays)
-Time (6 displays)
-Temperature (5 displays, 3 digits + "°" + "C")
-Humidity (3 displays...and any got idea, show to show a sign for percentage "%" ? Maybe 2x 2mm LED and a LED "bar"?)
-Barometer (8 digits (to show "0900 - 1050" + another 4 to say "mbar")

Thanks for any ideas!

is it capable to do it with a single ATmega328?

Yes but the display will be very dim because you will have to multiplex them at a ratio of 26:1. That means that any one display will only be on one twentysixth of the time.

Better solutions are:-

  1. a long chain of shift registers and drive the segments from them so they are on all the time.
  2. use the MAX2819 chip to drive 8 display digits at a time. You can string as many chips as you like on the the SPI bus.

@Mocivnik

You can try 30-digit cc-type multiplexed display unit based on the following Arduino UNO/NANO based circuit.


Figure-1: 30-digit multiplexed display unit


Figure-2: Arduino NANO based 16-digit multiplexed display unit based on circuit similar to Fig-1

@GolamMustafa:

THank you for your reply, but I'm not fammiliar with "cc-type multiplexed display unit".

I saw, that you're using 74LS154 as multiplexers, but I cannot figure out, what are those boxes, shown as "cc0-cc7" on the photo (and the rest).

Can you explain me that, please?

8-digit 7-segment displays, including multiplexer, are <$2 on ebay.
Search for “MAX7219 8-Digit”.
Multiple modules can be daisy-chained.
Leo…

cc-type multiplexed display unit

Common Cathode - it is one way of arranging the LEDs. The other way is common anode.

CC means that you put the CC to ground and power ( through a resistor ) to the segments.

Grumpy_Mike:
Common Cathode - it is one way of arranging the LEDs. The other way is common anode.

CC means that you put the CC to ground and power ( through a resistor ) to the segments.

Oh, yes yes. I didn’t realized, what CC stand for in this case, but now I udnerstand.

Wawa:
8-digit 7-segment displays, including multiplexer, are <$2 on ebay.
Search for “MAX7219 8-Digit”.
Multiple modules can be daisy-chained.
Leo…

I don’t like that because of rearrangments. I need different number of 7 seg’s in every line.