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Topic: Driving 26 7-seg LED displays with ATmega328 (Read 264 times) previous topic - next topic

Mocivnik

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!

Grumpy_Mike

#1
Aug 29, 2017, 04:17 pm Last Edit: Aug 29, 2017, 04:18 pm by Grumpy_Mike
Quote
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.

GolamMostafa

#2
Aug 29, 2017, 09:01 pm Last Edit: Aug 30, 2017, 06:29 am by GolamMostafa
@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

Mocivnik

@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?

Wawa

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

Grumpy_Mike

Quote
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.

Mocivnik

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.

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.

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