Gearclock

This is my animated Gearclock. It was produced using a 50 W laser cutter and includes a motor and microprocessor board with sensor to allow the clock to turn the gears on the hour.

I designed the clock using CAD software. I used an old copy of Pro-desktop to produce gear shapes, the frontplate and backplate along with the time ring. I assembled and tested my design in CAD to make sure everything would fit together perfectly.

Once everything was working in CAD I produced what I call a flatpack design in which the various components are aligned flat onto a surface and nested together neatly.

I exported the flatpack design as a dxf file which was then transferred into Rdworks on my laser ready for cutting.

Once all the parts had been cut I test assembled them using spacers under and over the gears and 4mm set screws and nuts as axles for the gears to pivot on. Plywood spacers also kept the front and back plates correctly aligned. I then cut some numbers from mirrored acrylic to finish the front view. These were simply glued onto the face.

Using a small geared motor which can be bought on the NET I checked the fit of the flats onto the motor to ensure there was no play and screwed through the front of the backplate into the holes on the motor with a couple of short self tapping screws. I then tested the motor and gear drive with a low voltage power supply at 3.3V or less. I had to run the gears in and lubricated them with silicon spray lubricant till they ran freely and quietly. I also made a plate to screw into the back of the motor to hang the clock from. Once happy with the assembly I superglued the 4mm nuts onto their set screws.

I added a Picaxe microprocessor board to the back of the backplate and a battery pack as shown. I used the picaxe 18x board power output 6 to turn the motor on and off. I added a small Linear Hall Effect sensor to the analogue input pin on the picaxe board.

I put the Hall Effect Sensor into the tube from an old ball point pen and mounted it through a hole drilled in the back plate such that it protruded to where the end of the minute hand would pass under the 12.00 position. I then superglued a small Neodymium magnet to the underside of the minute hand. I adjusted the hand so that it passed closely to the sensor by bending it. Because I used 5mm poplar plywood in my design I used a long reach clock module and was also able to add a stationary gear to the front of the clock to hide the mechanism.

Using the "readadc 0,b0" instruction I could read the Hall Effect Sensor value.

Using the "debug b0" command I could display the sensor level.

I quickly found that the sensor had an ambient reading of around 137 and firstly went up as the minute hand approached 12.00 o'clock but then dropped as it went beyond the sensor. I used this drop in value to trigger the motor and used a simple count routine to spin the motor for 0.5 sec once at 1.00, twice at 2.00 etc up to 12.00 o'clock. After 12.00 I simply reset the count. Above is the program I used.

It was handy to be able to trigger the mechanism independently of the clock mechanism. To do this I made a small wand with a Neodymium magnet glued inside it. By passing this by the sensor I could trigger the Picaxe chip and as such reset the count when setting the clock time. I also used the reset switch on the Picaxe during setup to quickly set the count to 1.