The Arduino controlled Electromagnetic Pendulum Clock

by Stephen Hobley on June 5, 2011

OK, only about 100 years too late – but I finally managed to assemble the clock works for the electromagnet-driven pendulum clock.

The primary drive is a 15-tooth ratchet. This is connected to two 60 tooth gears that creates the second hand drive. A 60:1 reduction gearing comprising 10:108 +18:100 (the largest gears) creates the minute hand drive. Finally a 12:1 reduction gives the hours.

The Arduino is not completely necessary, but it does allow offset/pulse width control, based on the readings it’s getting from the sense coil – so it’s completely justified in this instance (honest!).

I had to remove the front vertical bar as with both supports fixed it made assembly almost impossible – also it’s really important to make the spindle holders vertical position adjustable, as aligning the gearing always takes some additional work, post assembly.

Next thing is to create floor standing version, with a 2 second pendulum…


{ 7 comments… read them below or add one }

Coda June 7, 2011 at 3:57 am

Nice project. Where’d you get the gears?

Stephen Hobley June 7, 2011 at 7:29 am

CNC cut on my router…

Robert Chambers June 21, 2011 at 2:54 pm

And you’re going to bring this to our CNC Meeting on Saturday morning right?

Stephen Hobley June 21, 2011 at 3:07 pm

I really should, shouldn’t I? Hmmm…. I’ve got an unfortunate workload this weekend.

Let me see what I can do…

ron January 8, 2012 at 2:06 am

Great clock!
Can you suggest a good source for figuring out how to design the gears and gear ratios properly?


Stephen Hobley January 8, 2012 at 10:38 am

There are gear design programs out there –

you need a 1 second pendulum driving an escapement,
escapement/60 (eg.15 teeth to 60 teeth)
then 1/60 to get the minutes
then 1/12 to get the hours

The real problem is getting all the gears to fit into the space required.

Dick Bipes January 14, 2012 at 2:04 pm

Nice clock! I’v been working on one of my own. I started out with simple electronics, but switched to a TI MSP430 microcontroller similar to your Arduino. I’ve found that by varying the pulse width to the coil, I can speed up or slow down the pendulum by about 0.5%. By comparing pendulum speed to the micro’s watch crystal reference, the clock keeps quite accurate time.

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