# How to define the rotation of a mechanical clock?

Hey guys. So this isn't strictly arduino-related, but I really need your help.

I'w taken a mechanical alarm clock from the store and hooked up an arduino nano(and some other necesarry stuff) to it. My goal is to control the movement of the handles.

I soldered some cables to the coil of the clock and hooked up some transistors so i can change the polarity of the electromagnet, the clock is thicking as it should, just not in the right direction.

Somehow the movement of the little magnet controlling the "second" handle got flipped, and the handle moves backwards, and i have no idea what controls its movement.

I tried moving the magnet, or switching the poles in the program, but none helped.
I'll attach an image of how it looks like.

Please help me

This video shows how to take clocks like that apart and drive them forward and
reverse at various speeds. Pulse timing is critical.

This video shows how the pole shape and pulse timing work.

I don't know if it's relevant but some types of motor will run in either direction equally well. In order to make them run in the desired direction you have to start them spinning that way.

The clock motor is a single coil stepper, and one would think it would run equally well in both directions.

But it does not, due to an ingenious design (explained in the second video above).

lori2001:
Hey guys. So this isn't strictly arduino-related, but I really need your help.

I'w taken a mechanical alarm clock from the store and hooked up an arduino nano(and some other necesarry stuff) to it. My goal is to control the movement of the handles.

I soldered some cables to the coil of the clock and hooked up some transistors so i can change the polarity of the electromagnet, the clock is thicking as it should, just not in the right direction.

I think that ----- to you help you ------ you must first help yourself a little, by describing what it was that you actually did. You mention you hooked up some transistors for changing the polarity of the electromagnet.

"hooked up some resistors for changing the polarity" doesn't actually provide much information. You probably need to mention voltages, currents, power, waveform details being applied to the terminals of the electromagnet, timing details, connection details etc.

Maybe also mention whether or not the clock movement is always going in that 'reverse' direction - regardless of what polarity that was applied to the electromagnet.

Normally - before driving something, it's necessary to know procedure (waveform, power, polarity, timing etc) is needed - before driving that something.

Although - for some circumstances ----- if absolutely no information is available (due to it being historically lost), then I guess trial and error or reverse engineering needs to be done.

I think what you're actually trying to do is great. So my comment isn't about the goal. Only about details.

Jrem ----- thanks for your post. Nice videos!

BTW, how do the new "silent, no-tick" clocks work, BLDC motor?

Jrem's anwer helped me out. It works now =) thank you

PerryBebbington, it does run now in both directions, thanks.

Southpark, the voltage is 3,3V and I control the flow of electricity by 2 pins, the rest I don't know the answer to, honestly, because this is a rebooted 1-year-old project and I lost most sketches. Anyways, thanks for the info.

JCA34F:
BTW, how do the new "silent, no-tick" clocks work, BLDC motor?

I think it is more smaller steps. But I don't remember the source of this information.

lori2001:
Southpark, the voltage is 3,3V and I control the flow of electricity by 2 pins, the rest I don't know the answer to, honestly, because this is a rebooted 1-year-old project and I lost most sketches. Anyways, thanks for the info.

Most welcome lori. And very nice to hear you got it working!

JCA34F:
BTW, how do the new “silent, no-tick” clocks work, BLDC motor?

They have a similar stepper, just with more poles that runs faster.

// Per.