I wanted a sustain pedal for my keyboard and didn't have one. I've no idea how much they are and where you get them, but I wanted it right at that moment, so here's my little crappy invention.
Step 1: What It Does and How It Works
I realised that, at least on my keyboard, you can just shove a guitar-lead like jack in, and the pedal will be down whenever the wires are joined.
I didn't have a spare one to cut up, and they'd only just gotten rid of all the broken equipment in my music department, so I had to use a working cable, which I didn't want to destory.
All I needed to build then was a switch which connected the wires of a socket together, and I needed to put it in one of the 9V battery cases I had lying around.
The cable I chose was the one to my violin, which ha a much smaller, headphone-sized jack on the other end, which was better because I didn't actually have any bigger sockets around, nor would they fit in the little container. If you do have a broken lead you want to reuse, feel free to ditch having a socket on the pedal and just attach the wires directly to the switch.
So yeah, you'll need:
A used 9V battery
A push switch (I had a few left over from an old, failed project)
A socket if you want to not destory your cable (I desoldered it from a piece of TV equipment, they're pretty easy to find)
Tape, wire, etc.
Step 2: Make Case
Empty the contents of your battery. If you've never done this before, it's a matter of prying open the bottom with some pliers and removing the contents (which sometimes look like mini batteries).
I'd already done that and used the useful end for another project, so I'll be using tape to close it up, but if you hold onto both ends you can have it still look like a battery when you're done.
Step 3: Build Circuit
To activate the pedal the shaft and the tip need to be connected, and the ring does nothing. So basically, you just need it so all the pins on the socket are connected when the button is pressed.
Solder wires onto the switch and fold out the legs so they don't touch the case when inside. Solder one wire to the gound (that's the pin that touches the outside of the socket) and the other to the rest of the pins.
Or if you're just going straight to the lead, chop the lead's head off and seperate the two wires which'll usually be bunches of fine copper thread. Twist the both bunches and solder to the pins on the switch.
Plug in your device to your keyboard and see if it works.
Step 4: Fit Switch to Case...
My first idea was to put the switch at the end, so I could slot it into a drilled hole, but unless it was *right* at the end, it still wouldn't fit, so I had to make a cut and bend the metal back anyway, so you may as well put it in the centre.
So drill a hole in the case on top, and make a cut so you can pull the flaps back to get the switch in place and then close the flaps again.
Once you can get the switch in place, you can make a hole in the cap and put the socket through, and glue that in place.
Step 5: Stick It All Together
Glue the end in, or in my case, as I'd ran out of glue, I jammed it in with a bent paperclip. And as I said before, I'd already used the other end, so I covered it in tape.
Alright, so it's a piece of crap. But it's functional though, and that's what matters. I'd like to think that at least SOMEONE learnt something from this instructable, even if it's only that you only need to connect the wires to activate the pedal. I'd originally thought it sent data or something.
You could attach it to two pieces of board and a hinge to make it more pedal shaped, but I didn't bother.