FMC Assembly

The Opencockpits FMC Kit doesn’t come with any instructions, so here’s how I did mine in case someone else needs some assistance.

My build consists of:


1) First thing I did was assemble the tactile switches. This consisted of hot-gluing all the clear squares to the switches.


2) Before soldering the switches to the PCB, we need to add a 40-pin header to the PCB so we can connect our USBKeys Card.

You’ll need a 2×20 Pin 2.54 mm Double Row Header Strip.  I picked up a 010-pack of 2×40 headers off ebay for $4 and just cut 1 row in half.  The rest might come in handy later.


3) Next step was to solder these all to the PCB.

To ensure that the switches all lined up with openings in the plate, I screwed together the PCB spacer and what I’ll call the “switch guide plate” to the pcb (I used M3 size screws with hex caps). This allowed me to drop in a switch and make sure it was properly in place before soldering.

I would drop in 2-3 switches at a time. Then while holding them in place with one hand I’d flip over the FMC and solder 1 leg of switch just to hold them place. Then I could go back and solder the remaining legs without the switches falling out.

I repeated this until all the switches were in soldered in place.

4) After attaching the top plate to the FMC, I found the larger function buttons sank down into the unit pretty far and would need some additional spacers added.  I debated on what to use but since I really doubt I will ever backlight the unit I decided to use some white styrene I had on hand. I glued two pieces to back of the each button which gave them just the right height needed.   I think it might have been .010 styrene I used, but not 100% sure.

If you do plan on backlighting the unit, you can certainly use clear acrylic cut to size.

5) With all the plates assembled it’s time to glue the buttons into place:

I used Loctite Gel Super Glue.  Only a little dab was needed on the back of button, then just drop into place.  Repeat for every button.  Make sure your numbers are rotated correctly! You only a have a few seconds before the super glue sets.


6) Now it’s time for the electronics.  I ordered a 5.6″ LCD screen from Aliexpress. It was perfect fit for the unit.  I cut down the rows of pins along the backside of the PCB and then covered the LCD’s front frame with black electrical tape (don’t want any metal to metal contact on those pins).  Then I just hotglued the LCD into place.

You’ll also see the USBKeys Card install in the above photo.  I just mounted that to the mounting plate included with the kit and then screwed into place.  I bought some ribbon cable and IDC connectors to make a custom length ribbon cable as well.


7)  The FMC also has a few LEDs on it. These need to be connected to the Mastercard output card.  TO make the connection easy, I attached a small piece of 2-row header pins to the breadboard, hot glued to the Keyscard plate and then soldered the pins directly to the proper pins on the KeyCards.  1 ground and 5 LED controls.

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