How can I power a digital projector from my exercise bike so when you pedal the video plays?

It's for an installation I've made for an exhibition this sunday so I'm stuck for time! I want people to trigger the video (linked above) by cycling the bike.. I suppose I'd like to do this mechanically rather than electronically- rather than be turning the projector on and off all the time I'd like it to be always turned on and when the pedals start turning a piece of cardboard covering the projector lense is lifted, revealing the video. Would really appreciate any advice! xAoife

Re-design8 years ago
1. Mount a small wheel that has a slight friction. When the bike is pedeled it pulls a lever that tips the shutter. 2. Mount a magnet on the spokes and a magnetic switch on the frame. You can get these from a cheap bike computer. You'll have to come up with a circuit that will close a circuit when the pulses from the magnetic switch will open the shutter and close it when the pulses slow too much or stop. A motor or solonoid would open the shutter. 3. When the wheel is in motion there is some air movement associated with that movement. You might be able to harness that with a sensitive switch to turn on the motor or solonoid. There is a switch used in the vacuum system of some cars that will read the pressure dif. across a tee in the vacuum line. That difference if very very small. You might be able to use one of these to switch the shutter transport mech. I'm sure that there are lots of good ways to make this work without having to engineer a totally new process. Good luck.
aoife_abu (author)  Re-design7 years ago
Hi!

So sorry it's been a year since I asked this question and I never checked back to see if anyone had answered it! Just logged in for the first time today. Thank you so much for all your good ideas. We ended up with a pully system using an extendable dogs lead to pull a door away from in front of the projector...it worked...until people peddled furiously and got it tangled up!
Anyway just wanted to say thanks!
Aoife
jtobako8 years ago
Hook fan blades to the bike tire and have the wind blow a sheet of paper or curtain out of the way.
Re-design8 years ago
Just thought of the perfect solution. Install a generator made for powering a headlight for riding at night that will energize a motor that will open the shutter. When they quit peddeling a return spring pulls the shutter closed again.