Automatic Tubular Bells

Step 3 The motors and strickers

Next step was building the devices that move the striker sticks. This was another critical part, and as you can see in the pictures, I finally decided to use DC motors to move each striker. Each motor has the striker stick and a position control system attached to it, and is used to hit a pair of chimes. The striker stick is a piece of bike spike with a black wood cylinder at the end. This cylinder is covered with a thin auto-adhesive plastic film. This combination of materials gives a soft but loud sonority when striking the bars. In fact I tested some other combinations, and this was the one which gave me the best results ( I would be grateful if someone lets me know a better one ) . The motor position control system is an optical encoder of 2 bits of resolution. It is composed of two discs: one of the discs rotates solidary to the stick and has a black & white codification printed on its bottom surface. The other disc is fixed to the motor and has two infrared CNY70 emitter-receptor sensors which can distinguish the black and white colour of the other disc, and so, they can deduce the position of the stick ( FRONT, RIGHT, LEFT and BACK ) Knowing the position allows the system centering the stick before and after striking a bell what guarantees a more precisse movement and sound.