4 digit 7 Segment display with Arduino with Maxim7221

What You want to display can't be done by the above mentioned MAX. They are BCD encoders, Binary to Decimal. Back to square 1,2?

@Bin-Matloob
Read #16

Railroader:
What You want to display can't be done by the above mentioned MAX. They are BCD encoders, Binary to Decimal. Back to square 1,2?

The MAX can drive an 8 by 8 matrix of leds, no matter how they are arranged, or which leds are lit.

@Whandall.
Yes, absolutely. But it costst a lot more of Maxs. Dividing the display into BCD resp. ASCII would work. However, designing the info train of bits will call for lots of thinking, and coding, and wiring.

Railroader:
What You want to display can't be done by the above mentioned MAX. They are BCD encoders, Binary to Decimal. Back to square 1,2?

Railroader:
What You want to display can't be done by the above mentioned MAX. They are BCD encoders, Binary to Decimal. Back to square 1,2?

Dear, I have already made a prototype board for 2 teachers... which is working fine... Max library have its inbuilt function to display decimal numbers which will be in int variable.... well dont bother about it...

my concern are two only, which I repeated many times.

  1. Which Arduino board you suggest me to adopt? ( I think 2 Mega, Master/Slave)

  2. Can I use Arduino single "Clk pin" for all 40 no. of Maxim7221 (Pin no. 13) ?

Railroader:
@Bin-Matloob
Read #16

80 no. of 4 digit 7Segment display

Whandall:
The 'explanations' don't make sense to me.

Shall I elaborate 4 section idea more?

To send data to a package of cascaded MAXs any Arduino would do. Your project needs RAM to keep the info that will be displayed so reading the specs for the capacity of memory of the different Arduinos will be good.

Your 2 questions have been handled above. Maybe too many "helpers"....

Railroader:
But it costst a lot more of Maxs.

No, each 8 digits/symbols/letters need one MAX7221, 80 groups of 4 digits need 40 MAX7221.

Railroader:
Dividing the display into BCD resp. ASCII would work.

No need for that as far as I can see.

Railroader:
However, designing the info train of bits will call for lots of thinking, and coding, and wiring.

No. Maybe some copy and paste from MAX-libraries. The wiring is trivial__*__ and only depends
on the fan-out/fan-in ratio of the Arduino output and the MAX7221 input pins.

__*__You only have to connect the modules, I would use off the shelf ones.
If not readily available, I would design and produce a pcb for the MAX/display connection.

Bin-Matloob:
Shall I elaborate 4 section idea more?

Hm, not really. Lets focus on the hardware.

You want to drive 80 groups of 4 LED digits (normally the eighth segment is used as a dot), correct?

And we are talking about the normal small LED digits, not some giant 24V variants, correct?

@Whandall
yes,
Im going to use 1 inch size (Length) segments

picture attached for your refrence

@Whandall

The origin of the question is :

I Planning to make a 7 Segment LED Display board Showing item list of 80 items.

8x8 is not mentioned.

@OP
Using a 4x1 LED saves You from wiring. Good choice.

Railroader:
@Whandall

The origin of the question is :

I Planning to make a 7 Segment LED Display board Showing item list of 80 items.

8x8 is not mentioned.

When I said 8x8? I dont want 8x8... I think still u r confused? see the shared img. :slight_smile:

Railroader:
@Whandall

The origin of the question is :

I Planning to make a 7 Segment LED Display board Showing item list of 80 items.

8x8 is not mentioned.

80 entries of 4 numbers/letters/symbols displayed on 7-segment led modules..

8x8 is implied by using a MAX7221 and refers to individual leds here in 8 groups of 8 (7-seg + dot).

8x8 was mentioned by Whandall. It involves something new and confuses.
I opened Your link to the 4x1. Good choice I think.

ok no issue…

  1. So shall I go ahead with common clk and load/cs Pin for all 80 7Segments? :slight_smile:

  2. will it ok to cascade all 40 Max? like 1max Dout —> 2Max DIn —> 3Max Dout…80Max In

will it work?

As I see it, yes.
Start testing by using 2 MAX and LEDs and get hold of things. Then expand.
Once again, check what characters, and how, the MAX needs to be accessed.

Bin-Matloob:
2. will it ok to cascade all 40 Max?

What did the datasheets tell you?

Are you really expecting me to search for that information and/or test it in reality?

You can make a chain of 40 max7221 work on any Arduino,
it could be necessary to add some minor additional buffers/drivers.

You could buy 40 modules like these 10 modules.
maxmodules.png
and perform real tests.

The above is only an example, there are cheaper modules on aliexpress.

maxmodules.png

Bin-Matloob:
Im making a School teacher display board... that school contains 80 teachers staff... So display board will show status of all teachers...in front of their names details like Class (0-12), Section (A,B,C,D,E,F) of respected teachers...

So you DON't want 7-segment displays (they can only display numbers, not letters).

8*8 matrix displays (1 1/4" is common), and the Parola library, is another option.
One of the many example pages here (watch the video).

Can be daisy-chained as well, using only a few pins
I think two Megas is a bad idea with messy coding. Get a small Arduino with more memory.
Leo..