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juleiin
Posts: 54
Hi,

I want to make a PCB to make things way more cleaner than all the wires going behind my FCU. (at least to make a common ground pin)

By doing this I realized I could do my own max7219 tube with different number of digits per tube.

But is it possible to control one 7-segment digit (8 of them via a max7219) or does it have to be 4 + 4 ?

What combinations are possible ? Ideal would be 3 + 3 + 5 + 5 but 3 + 3 + (2+3) + (2+3) could also be great, even 1+1+1+1+1+1+1+1+1+1+1+1+1+1+1+1 (SPD/HDG/ALT/VS digits)

Thanks,
Julien
2018-06-14 13:13
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StephanHo
From: EDDG, Germany
Posts: 1719
Supporter
Hi Julien,

the standard is 8 digits per MAX7219. But how you divide them for your own purposes is up to you.

Look here. https://www.mobiflight.com/forum/message/4760.html

or here https://www.mobiflight.com/forum/message/4053.html

The possibilities are very diverse. You can search here in the forum or via google.
Grüße,
Stephan
2018-06-14 14:15
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juleiin
Posts: 54
Hi thanks for the answer but what I meant was creating the PCB (we normally buy it with max7219 tube) and place digits wherever I want on this pcb. This to free up space behind the panels. And the question was do I have to use 4 digits segment display or can I use 1 digit 7 segment display that I can place wherever I want (like 3 for spd, 3 for hdg..) and control them by the max7219 ?

When I look at max7219 datasheet it looks like you can only split the 8 digits in 2x4 and not 1x8 or 2x4.

Julien
2018-06-14 14:32
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pizman82
Moderator
From: ETSI, Germany
Posts: 4703
Supporter
Hi.

You can use 1 Diggit Displays.... And thats the best technic, too. Professional Cockpitbuilders work mostly with 1 Diggit Displays.

The Datasheet of MaxTubes talk about 2x4 cause they designed the PCB´s in that way.

Basicly your MAX got 16 Lines that are needed to run you Display. 7x Segment Lines + 1x Decimal Point + 8x Common Cathode Diggit Lines..

In the Tubes this are split in 24 Lines ( 2 Blocks) Each block got 12 Lines .... 8X Segment/DP and 4x Diggit .
So the Segment Lines for Left and Right 4x1 Block are just duplicated .

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For your system:

If you plan to set the RAW Max Chips ( like this ... https://www.ebay.com/itm/IC-MAXIM-MAX7219CNG-Max7219-IC-DRIVER-LED-DISPLAY-8DGT-24-DIP-/400551851482 )
then i will recommend to use ONE Chip for each Display.
Thats more tidy as you will split 1 MaxChip for example to 2 Displays ( 1x3 1x4 )
Don´t care about the empty 5 possible Diggits if you use only 3 Diggits by one Max.... For 0,99$ thats realy not a problem.

If you want to use more Displays to ONE Max than think about..... ONE Config MUST get to ONE Max.
Yo you can not easy say for example a 5 Diggit Display like MCP ALT should show 3 Diggits on Max A and 2 Diggits on Max B. Here you need then 2 Configa... A lot of work to set it and maby problems if you have bugs.

Summary....
I would use this chips direct on PCB .... Use 1 chip for every Display .... Use 1 Diggit Displays. If you need a 5 Digit Display use 5x1 Diggit Displays and set it together.
On PCB design lines from Max Chip to Display .... 8 Segments and Number of Digits for Daalines ( a 5 Digit Display got for example 8+5=13 Lines )
The Digit Lines must go individual to each Digit Connector spot.... The 8 Segment Lines can be used only 1 Time and can be chained from Diggit to Diggit on PCB.

Finaly i would do the Power, CLK , CS lines ( and DIN DOUT ) on the PCB too.... So finaly you have a Connector for all Displays to MEGA.

If you like it extremly professional you finaly can build a Pin Socket where you simply connect the hole Mega form behind. Then the Hole Element (Including the Mega) is without wires. You only get a USB Connector and all other things are on PCB.
Good Luck !
2018-06-14 17:00
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juleiin
Posts: 54
Thanks pizman! I'll design the pcb with this method.

And for your last trick, that was exactly what I planned, pin headers taking the footprint of the mega, and just have to plug the mega from behind!

I'll keep you update with the pcb :)

Julien
2018-06-14 19:44
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thatchi
Posts: 166
Juleiin. Check out this gentleman webpage https://flyingforfun.weebly.com/cessna-172-cockpit.html/
It is designed for Cessna 172 , but the concept can be adapted to other addons easily .
2018-06-14 21:21
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pizman82
Moderator
From: ETSI, Germany
Posts: 4703
Supporter
That Link is Albeagles Page... A High advanced Member of this comunity !
https://www.mobiflight.com/forum/message/7039.html

Maby you should open a contact to him by email or private com.... He can give you pretty shure lots if input for your project. Realy nice guy ! :thumbup:
Good Luck !
2018-06-16 13:44
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