murthy@arnor.watson.ibm.com (Sesh Murthy) (08/24/90)
A friend of mine would like to change the speed up a clock by a factor of 2.0 or 0.5 for a psychology experiment. I was wondering if there is any simple way to do this. I know that the commercially avialable battery driven clocks use a crystal, bring down the frequency using a divider and then drive a stepper motor. This then drives some gears that drive the minute and second hands. I figured that changing the voltage would not help in this case. Is it possible to change the gearing or the crystal frequency in a simple manner. I am willing to buy a clock in kit form, if these are available, and then put a divider in the circuit which can be switched on and off by a switch. I think gears are an inelegant solution. The other things I though of was to get a wall clock that operates on 50 Hz, 110 v and somehow double the frequency of the current. Would this work? Is there a simple way to double the frequency of the Ac going into the clock. The two ways I could think of doing this were 1. Have a motor pair, and vary the speed of the motor and hence the frequency of the current generated by the AC generator. 2. Use an SCR to chop up the incoming sinewave so as to double the frequency. Will this work? If someone can tell me of a simpler way of doing things, or a simple way to implement any of these ideas, I would be grateful. Thanks Sesh Murthy
francis@hydracs.ua.oz.au (Francis Vaughan) (08/24/90)
In article <1990Aug23.173721.7942@arnor.uucp>, murthy@arnor.watson.ibm.com (Sesh Murthy) writes: |> A friend of mine would like to change the speed up a clock by a factor |> of 2.0 or 0.5 for a psychology experiment. |> |> I was wondering if there is any simple way to do this. |> A nasty thought comes to mind. Clocks as a rule run on the proverbial "smell of an oily rag" so this should work. Get a signal generator, a small lab audio amplifier and a power transformer. Run the transformer backwards from the amp which is fed with a nice sine wave from the signal generator. Need a bit of care in setting up to get the volts OK, but you also get infinitly variable time. Use an oversized transformer, so you don't saturate it on low frequencies. Francis Vaughan.
bill@videovax.tv.tek.com (William K. McFadden) (08/24/90)
The easiest way to do this is to run a variable sinewave oscillator (e.g.,
audio gernerator) into an audio power amplifier. Connect a standard AC wall
clock to the amplifier's output. With the frequency set to 60 Hz, gradually
increase the amplitude until the clock seems to be running normally (or use a
voltmeter to set the voltage to 120 VAC). To change the speed of the clock,
vary the frequency.
You will need to use a PA amplifier with a 70V output, since the 8 ohm outputs
on regular amplifiers don't put out enough voltage. If all you have is an 8
ohm amplifier, you can get a transformer from Radio Shack for about $5 that
adapts the 8 ohm output to 70 volts.
BTW, I have heard stories of coworkers doing this to chronic clock watchers.
They would set the clock to run slightly fast or slightly slow, being sure to
vary it a little every day. Drives 'em nuts!
--
Bill McFadden Tektronix, Inc. P.O. Box 500 MS 58-639 Beaverton, OR 97077
bill@videovax.tv.tek.com, {hplabs,uw-beaver,decvax}!tektronix!videovax!bill
Phone: (503) 627-6920 "The biggest difference between developing a missle
component and a toy is the 'cost constraint.'" -- John Anderson, Engineer, TI