Arduino Tower Clock (Part 2)

I documented my adventures with a tower clock about 7 years ago .

It has kept working over that time, but I have had to replace the minute hand drive motor a couple of times as the gears had stripped teeth. The latest one uses a helical (worm) gear, and has proved to be far more resilient, lasting over 3 years at this stage.

However the bell drive mechanisim has proved to be more problematical, which isn’t surprising seeing it is dealing with a 3.5kg weight. Initially I had two motors (the same as the hand drive motor) driving a shaft (to share the load), which had a wheel attached, which pushed the other end of the hammer arm. I was using measuring the current drawn through the VNH5019 Motor Driver Shield. Sadly the motors finally gave up.

I then went to a wiper motor, using the internal home position switch to shut it down, but that too burnt out after a couple of years and I couldn’t get a direct replacement. I think things shifted mechanically to cause that. Certainly when building things for a bell ringer, it has to be durable!

I tried using some solenoids to pull the hammer up directly (via a cable), but they lost power very quickly so I gave up on that idea. They were expensive and drew a lot of current.

I then went to a Choo Choo mechanism using a a 12V car jack motor that a friend had lying around. He used a cam to stop the motor at the right position. You can see this working in the video below (the cam is the white cylinder, and you can see the micro switch on the left):

I have a 12V power supply and solid state relay in the plastic box in the background. You can see what is at the other end of the wire in this photo:

The purpose of the stainless steel frame is so I could adjust where the cable is attached (changing the mechanical advantage) and also so I didn’t need to modify the original clock parts in any way (an important issue in this case). As it worked out, the choo choo mechanism was able to handle the maximum load, so the bell is now again as loud as it was originally.

This system has now been working reliably for a year.

Leave a Reply

Your email address will not be published. Required fields are marked *