Simplified EFIS and FCU for A320

General Information

I created this simplified version of the Captains Side EFIS and the FCU completely from the scratch.

Like all the other models i created for my home cockpit, following rules apply here, too:
- print more, buy less
- all modules /models must be “one independent block”
- despite many other designs i do not use 3 panes (e.g. front, button holder, back) - therefore no backlight - and no professional manufactured PCBs
- As far as possible i use Standard Arduino Mega (no Pro or Mini) and the software "Mobiflight"

Attention, for the EFIS-FCU-Block some knowledge about 3D-Printing, Electronics, Soldering and of course Mobiflight are required.

The front plates and some knobs are in BambuLab 3MF format as they are two-colored.

In addition to the print files here and the BOM i use the Push-Pull-Rotary and the Push Pull Rotary with selector switch. Please see there for the parts to buy in addition to the BOM.

The whole block is designed to be connected with USB and external power source (absolute needed due to the load) to my Main Pedestal and holds the Arduino Mega, the Breakout System Board from Mobiflight (for the 7-seg displays) and all the other electronics.

Attention: if you follow my overall design and connect this external EFIS-FCU-Block with a approx 2m cable to "a main box" a 5V line won't work as the voltage loss and the noise on the cable will be to high.
Therefore a bluk converter (12V to 5V) will be placed into this box and will be connected to a 12V power supply in the main box. 

Exploded Drawing shows how all the parts are fit together - top and back pane where moved to get a view inside.

The front plate with its controls can be used without my housing as well, but then the display holders etc. must be designed accordingly.

BOM

Some M3 Self-tapping inserts: https://www.amazon.de/dp/B07QX74XSN
One DM13A Constant LED Driver: https://de.aliexpress.com/item/1005011863112827.html
Two Multiplexer: https://www.amazon.de/dp/B09VXV67DQ
13 Momentary KD2-22: https://de.aliexpress.com/item/1005004959764864.html
White LED Displays: 2x3 digits, 1x4 digits, 2x5 digit (Best price on AliExpress, at this time here.
5 White 5mm LEDs
2 push buttons 6x6x4,3mm
2 3-pos Switch: https://www.amazon.de/dp/B0F3H4F6M3
MAX Breakout System Board: https://shop.mobiflight.com/product/max7219-breakout-system/?v=15fc885b9ab6
One Buck-Converter 12V to 5V: https://www.amazon.de/dp/B0GWDY2PM5
Some M2x6 screws with nuts
Some M3x8 and m3x12 screws for the housing

It is possible to make the displays running with some MAX7219 Chips and direct soldering on your own, but it to ease the effort a little bit, i used the mentioned board.

Electronics

As the connectors to all the buttons, leds etc. are to many to fit on a prototyping board for the Arduino Mega i created a so called connector board (approx. 155x108mm) for holding all the chips and the connectors.

This board is a perfboards PCB and manually wired. The connection to the Arduino Mega is made by one 24pin and one 10pin flat cable connector. The small one has the control signals for the Multiplexers and the LED Driver, the bigger holds all the connectors for the encoders, turning switches and 2 of the 18 LEDs.
All other buttons and leds are connected to the Connector Board with the Mulitplexers and the LED Driver.

Also the 7-seg displays are soldered to small perfboards PCBs which are mounted to the display holders.  

Wiring

All buttons, leds etc. are connected with flat cables directly soldered to it and JST connectors on the other end to be plugged to the connector board.
If you want to follow my design send me a DM and you will receive an table with the wiring logic and a Paint.Net file where all the wiring is shown in different layers.
Not nice, but working ...

Assembling

• Print all files and combine the 2 pieces of top, back and bottom each with 2 M3x8 with nuts

• Assemble the front plate with all control parts

• Mount the Arduino Mega, the Breakout System Board and the "Connector Board" on the bottom pane

• Connect the other boards to the Arduino with flat cables, ideally routed underneath the connector  board

• Mount the both side parts to the bottom plate

• Connect all allready wired controls from the front pane to the connector board and mount the front plate to the existing block

• Finally plug in the Arduino USB-cable the the external power supply, block the cables with the Block-part and mount the back and the top case pane.

Update October, 31st. 2026

As i power this box with 12V instead of 5v to eliminate any loss or noise and converting it to 5V in the box the buck converter will be mounted at the case right plate. As these convertes have tolerances in the width and some hold tight and some fall off hold it in its place with the buck holder clamp.