keypads and buttons
Designing the keypads
Custom PCB's are pretty easy and cheap to get manufactured for a one off project nowadays, so I began by researching how to get it started. After playing around with a few online PCB design programs, I decided the learning curve was too steep and just gave up. True story. For this project I had already spent lot of time learning Arduino and DCS-BIOS, not to mention CAD design in FreeCAD, and laser cutting and 3D printing. I just could not be bothered, nor did I have the time, to learn PCB design as well.
There are only two large keypads required for the A-10C, the CDU and the UFC. Both are pretty straightforward designs, so I decided to make them myself on prototype PCB's. I made the CDU first. At the time I had a 5 inch LCD screen, that had a HDMI input that would be connected straight to the computer. For the keypad, I used prototype PCB board to mount tactile push buttons. When designing the panel in CorelDRAW, I spaced the keys to be the correct distance so that the buttons mounted on the 2.4mm pitch prototype PCB would be in the centre of the key.
I did try some cheap LED backlit tactile buttons, however found that when illuminated they were far too dim to be effective. Tactile buttons with quality LED's in them are much more expensive that normal tactile push buttons, and for the CDU and UFC I needed 111 buttons (77 in the CDU and 34 in the UFC).
I decided to use much cheaper, non-illuminated tactile push buttons, and I would just use inexpensive LED strip lighting for the backlight.
The tactile buttons I use for all keypads. They have a 16mm long shaft, long enough to get through the spacer panels and touch the rear of the buttons. They can be easily trimmed with a sharp knife id they are too long.
The tactile buttons mounted in prototype PCB. The clear panel is a spacer for the CDU, and the square cutouts in it allow me to make sure the buttons are perfectly positioned before soldering them in place.
Close up of the keypad assembly.
The keypad assembly mounted to the spacer, with the backlight LED strip stuck on and ready for wiring. The cheapest self adhesive LED strip i could find on eBay. You could even use RGB strip if you wanted too.
Wired up and ready for testing.
The Green 12V LED strip illuminated.
How it looks with the panel and buttons on top. The light bleeding around the number buttons is because they are not yet mounted properly, just resting in place for the photo.
The same keypad design used in the CDU was used for the UFC.
LED Strip illuminated.
The front spacer on the UFC in position. This spacer was made so the front panel could bolt into for the old, non 3D printed UFC Case. When I printed the new one this spacer was completely removed.
LED's illuminated
And the front engraved panel mounted.
Parts of a buttons layed out. From left to right, the 3mm white top, the 2mm white bottom, glued together and painted, then engraved. Note that this one was a failed button, as the engraved square wasnt centred. I made almost twice the number of buttons i needed, and only the best ones made it into a panel.
A selection of buttons glues and ready for paint. You can see the design of the longer rocker style buttons.
From left to right: the 2mm white bottom with tabs on the side to fit notches in the panel which keep them in place and allow them to rock. The 3mm white top (with the protective paper still on). The next next one is the two glued together and painted, then the last one has been engraved. Another failed engrave as the arrows are not centered.
An early error in the design of my round button caps. I later made them again like on the left, with the rear part square. If round, the button will be able to freely rotate in the panel and you will end up with upside down text.