I’ve been confronted recently with a limitation of my home made arcade joystick : I’m unable to play Mortal Kombat with it, it lacks buttons. I’ve build my joystick on top of two xbox 360 joypads where I’ve connected the A, B, X, Y, LB and RB buttons. But it’s not enough as MK uses also the LT and RT triggers. The details on my joystick are only available on the french side of blog as I’ve made it some months ago … sorry about that. 

All the buttons I’ve connected so far were simple and straight on/off buttons, but here, the triggers are small potentiometers (10K Ohm) as you can see on the following picture :

To simulate the behaviour of the potentiometer, I’ve simply considered the two extreme positions by using an inverter button and two resistors. In idle position, one side is directly connected while the other goes through a 10K Ohm resistor. When pushed, it’s the other way round … The following schematic shows what I had before and what I have now : 

This is how it looks like once soldered on an arcade microswitch : 

The soldering on the joypad board was much more simpler than the other buttons. I just removed the potentiometers using a desoldering pump and than had a clean place to connect my three wires. The whole thing is covered with hot glue to avoid any unwanted wire movements.

For ergonomic reasons, I’ve put my two new buttons right under the other six ones.

I’d liked also to move the joypad leds on the front panel of the joystick in order to see if the joystick is switched on and who is connected. Unsodlering the surface mounted leds is not that simple, but soldering afterward wires on a such tiny surface … I just don’t feel it … If someone has already done that kind of stuff, I’m really intersted to know how and what tools to use :-) …