eDrum can be configured to use three type of pedals: 1 switch, 2 switches or potentiometer.
A switch based pedal has basically one switch mounted inside, that is normally open when Hihat is open, and closed when Hihat is closed. Connect it to a normal "guitar" jack, and it just works.
Two switches can be used to have also a half-open Hihat note, when only first of two switches is closed. For construction, see below.
And the last posibility, but one of the best sounding, is to connect a potentiometer to a analog input and have 8 different hihat notes ranging from fully closed to fully open.
This is the pedal I bought in a local electronic shop for about 6 euro. It is a good candidate for what I'm trying to do.
It has two switches inside, making contact one after other. It is made of plastic and it moves about 1cm from open to closed. Opened looks like this:
Connection of those two switches is simple, wire them to 6,3mm stereo jack and ground, like this:
After some brainstorming :-) I came up with this idea. A no-mechanical-parts, optical HiHat pedal. It is based on light dependent resistor (LDR) as a sensor. LDR is illuminated by the high luminosity LED from a short distance. Between LDR and LED, there is a optical barrier, moving along with the pedal. It will attenuate LED's light, changing LDR's resistance. It sounds complicated, but it is simple:
A few component are mounted on the back of the PCB.
Look at the right side of the picture. You can see a small "L" shaped black part that will act as "light barrier" for optical sensor. It is just a piece of plastic, glued to the pedal.
You can clearly see that the sensor light will be attenuated by introducing that plastic piece between LDR and LED.
This is the interior of the pedal, mounted.
More details soon!