PENdulum test (BIC actually)

Here's a short video of my testing my pendulum system out, it's running a little fast so I need make the pendulum longer and the only way to accommodate t in that case is to raise the top and the coil up higher. I've already mover the opto sensor to the back and have a little pin in the back of the pendulum interrupting the beam. Even though the stanley knife bade fulcrum should be pretty well friction free bcz the coils magnetism has to jump a bit of a gap it's not so efficient and those 60 pulses a second are going to eat the batteries! Maybe a solar panel on top?