The project this week was to make an output device. I wanted to try out two types for my final project: a stepper motor and a solenoid. The stepper motor was relatively simple. I had some trouble stuffing the board because I accidental soldered a mosfet where the voltage regulator needed to go. They look almost identical. The voltage regulator should say "LOB" on it. I attached a guitar pick to the motor which has enough force to strum a string but may require a better attachment method than tape if I want it to last more that a few strums.
The second type of device I wanted to try was a solenoid. Solenoid are typically expensive in the range of $15 - $30 a piece as compared to a few dollars for a stepper motor. This would be a limiting factor for my final project which would use 20 - 50 of them. I decided to try and make one since they are fairly simple in concept. I found some spare parts including an aluminum tube spacer, a long ferrous screw, two magnets, coated wire, and some electrical tape. I wrapped the wire around the aluminum spacer as much as I could. I would recommend using a spool-shaped spacer with flanges which will keep the wire in place. I taped the wire on though glue can be used as well. I also scrapped the coating off the ends of the wire to connect the circuit. The solenoid shaft was a ferrous screw with a magnet at each end. The magnets just help. increase the effectiveness of the magnetic field with out requiring more current.
I found the solenoid was really weak. It would probably not be enough to press a string down. Some ideas to increase the force of it would be to wrap more wire around the spool, decrease the wire size, increase the strength of the magnets or increase the current.
We noticed during testing that even while increasing the current, the force did not increase. This was probably due to the size of the wire I used. Though the current was increased, the solenoid was only pulling a fraction of it. For my next iteration, I am going to try to increase the amount of wire wrapped around a flanged spool to get a larger magnetic field around the core.