Clock with two stepping motors

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saunj

Senior Member
I got started on this project because I added my two-pennies-worth to the comments on alpacaman's wooden clock about using mains-frequency timing to time a clock. To my mind it is not worth the effort of using an AC transformer and adding a rectifier, filter and squaring circuit when for about the same price and effort you can use a watch crystal. In addition to using a wristwatch directly, as in my comment , I have five times made my own oscillator. Two used Dallas ICs,one a Ds1302, and the other a Ds1307. Three used CD4060s, which provide a 4-Hz signal. Both can be trimmed to exact frequency, and will run for years on a coin cell. Plus, the Dallas ICs provide the date and some memory to boot.
After making that comment, I thought I would do it again with a watch, using a better interface circuit. By using an op-amp to provide the watch's pulse current, no dropping resistor needs be used. It turned out to be more trouble than using a crystal oscillator, but having made it, I wanted to use it. About this time after reading up on servos, I felt that I preferred stepping motors, especially for a clock. It helps that I have no servos, but I do have several stepping motors, recycled from 5 1/4" floppy disk drives.
Not wanting to compete with alpacaman's beautiful handiwork, I used a dial from an old Las Vegas souvenir clock, whose movement had expired. However, since the apparatus is self-contained, it can be put behind the dial of any large clock. I selected two 200 steps/rev motors, but had a problem hooking them up to the coaxial hour and minute shafts. Fortunately, I have a brass bevel gear set from a ham radio condenser drive, so the hour motor could be put underneath. To couple the motors to the shafts, I used short lengths of fuel hose. The shafts are from an old dual potentiometer.
The Picaxe is an 18X, to drive the eight coils via a ULN2804. It, and the watch circuit, are powered from a 3.6V cordless-phone battery, so they are independent of the line-powered motors, which use a 12 volt "wall-wart". If the power fails, the Picaxe counts the lost seconds, and advances the hands after power is restored. It also corrects the timing of the watch, which runs fast.
For full details see: http://projects.worsleyassociates.com/Stepping_Motor_Clock/index.html?
Note: I have now posted my code in downloadable form in:
http://projects.worsleyassociates.com/Archive/index.html
 
A

alpacaman

Member
saunj said:
I got started on this project because I added my two-pennies-worth to the comments on alpacaman's wooden clock about using mains-frequency timing to time a clock. To my mind it is not worth the effort of using an AC transformer and adding a rectifier, filter and squaring circuit when for about the same price and effort you can use a watch crystal. In addition to using a wristwatch directly, as in my comment , I have five times made my own oscillator. Two used Dallas ICs,one a Ds1302, and the other a Ds1307. Three used CD4060s, which provide a 4-Hz signal. Both can be trimmed to exact frequency, and will run for years on a coin cell. Plus, the Dallas ICs provide the date and some memory to boot....
Click to expand...
Nice job on the clock. I appreciate your use of the wristwatch for the circuit timing. The big adavantage I see, over using mains for timing, is that you don't have to reset the time after power goes out.
However, I think that there is a misunderstanding on how I'm getiing the signal from mains, how complicated it is, and how much it costs. The only extra parts I'm using is a $0.22 transistor and $0.002 for 2 resistors. I was going to use a power supply to power my clock anayway so the transform, rectifier, and filter were required regarless of how I do the timing. The single transistor and 2 resistors are the only squaring circuit. So it's a really cheap and simple way to get timing for a clock if you're going to have a power supply to power your circuit and if you don't mind setting the time after a power outage.

Anyway, we all have our reasons and prefferences so do what works for you.

Again nice job and I'm very tempted to use your method for clock timing in the future so I won't have to reset the time when power goes out - which happens way too ofteen.
 
hippy

hippy

Ex-Staff (retired)
Ont thing to note is that a watch crystal can be connected directly to some of the PICAXE's, certainly the 08M and 18X, and that could be used directly or as a standalone module to provide a 1Hz signal, even doing both crystal and mains timing. It does involve some twiddling with internal SFR's.

I've used an 08M and 18X with watch crystal and no capacitors and that might suit mains frequency timing with the inaccurate crystal filling in when mains fails. Code could get pretty hairy so perhaps best used as a separate module for driving the rest of the system.

http://www.picaxeforum.co.uk/showthread.php?t=7142
 
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