| Gear Clock |
I can't take credit for the design of this one. I bought the
gear as a clock a few years ago. It was mounted on a frame
and had one of those cheap clock units running it. The
gear is designed to be driven by the minute-hand shaft of
the clock mechanism.
The problem was that it kept breaking. I think the problem
was that the clock mechanism wasn't strong enough to hold
the weight of the gear.
gear as a clock a few years ago. It was mounted on a frame
and had one of those cheap clock units running it. The
gear is designed to be driven by the minute-hand shaft of
the clock mechanism.
The problem was that it kept breaking. I think the problem
was that the clock mechanism wasn't strong enough to hold
the weight of the gear.
I bought a stepper motor with four input wires. A PIC
16F676 microcontroller functions as the timer. Every
three minutes, four output pins are driven either high
or low for half a second. These are each connected to
a pair of transistors - one PNP, one NPN to drive the
motor with more current. The stepper motor rotates 18
degrees each time.
16F676 microcontroller functions as the timer. Every
three minutes, four output pins are driven either high
or low for half a second. These are each connected to
a pair of transistors - one PNP, one NPN to drive the
motor with more current. The stepper motor rotates 18
degrees each time.
The circuit and motor are mounted in a piece of PVC
tubing. I drilled a hole from the back of a closet so that
only the shaft of the motor sticks out of the wall. The
original little gear is mounted on the shaft and the big
gear hangs from it. A pack of 8 rechargeable AA
batteries in the closet power it and last several weeks.
tubing. I drilled a hole from the back of a closet so that
only the shaft of the motor sticks out of the wall. The
original little gear is mounted on the shaft and the big
gear hangs from it. A pack of 8 rechargeable AA
batteries in the closet power it and last several weeks.