Speeding up wall clock with arduino?

Other Hardware Motors, Mechanics, Power and CNC
1

I have a wall clock, powered by 1xAA battery. I want to use arduino to make it go faster or slower. I don't
need the actual speed, I need overall time periods modified (like 30 actual minutes is 40 on that clock, don't ask why.). Mehods I thought of:

  1. Digital pin to battery +, gnd to -, (alongside with the battery), giving it 10 sec "boosts" every minute;
  2. No AA batt, pwm to +, gnd to -, power goes from arduino, only the speed is modified sometimes; can I do it without frying something?
2

Battery clocks are timed by either a conventional escapement wheel or a crystal oscillator. Neither of these can be altered without being extensively "re-engineered". What you need is a "slave" clock that is driven by timed pulses originated by some master clock. These were generally used in industrial situations with one master clock feeding numerous slave clocks around the site. The slaves were simple solenoid driven ratchet mechanisms with the solenoids being pulsed, typically once per second, to drag around the indicating mechanism. The attached link shows an example

You can set the pulse rate to suit your application.

3

I would try to remove the cover of the clock movement to gain access to the crystal, which will almost certainly be a 32768Hz crystal in a metal tube. Disconnect it, and feed a 32768Hz (or thereabouts) signal generated from the Arduino through a 100K resistor to one of the pads that the crystal was connected to. If that doesn't work, try the other pad. You will need to connect the negative battery terminal to Arduino ground.

Once you get that working, you can adjust the frequency to vary the clock speed. You biggest problem is likely to be gaining access to the crystal.

4

Hacking a quartz clock movement to bypass its original timebase and replace it with your own is described here:
http://www.cibomahto.com/2008/03/controlling-a-clock-with-an-arduino/

A good application for this:

5

It doesn't have the "tick" sound or handle switch. The seconds handle is moving all the time, continuously and smoothly. Maybe that means it has no quartz regulator and I can speed the motor up just by adding a little more voltage?

6

Rob3rt:
It doesn't have the "tick" sound or handle switch. The seconds handle is moving all the time, continuously and smoothly. Maybe that means it has no quartz regulator and I can speed the motor up just by adding a little more voltage?

I'd be surprised. A battery-operated clock that depends on input voltage for accuracy wouldn't be a very good clock. If it's not quartz, I'm not sure what it would be.

7

Clocks do NOT use their supply voltage to regulate their speed. Previous posts give you all the links you need to hack the oscillator and get you there. As to the continuous movement, if you used a high speed camera you'd see that the continuous movement was actually the integration of lots of small steps. The human eye is pretty useless at high speed step discrimination - it wasn't necessary as part of the evolutionary process so simply didn't happen. Nature is pretty good at avoiding unnecessary complication.

8

I don't need it for camera speeding, If I would, I'd just use after effectsmmasking and timing.