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Stepper Motor Control

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vtsteam:
Yes Phil, I think traditionally here at least the mains cycle count for the day was tweaked at night by the utility with small adjustments to frequency so clocks and other synchronous devices would stay on time. Not sure of that -- just some information remembered from long, long ago, source unknown. Could be non-urban legend.  :)

Easy to do if you have a standard clock (or clock signal) and a synchronous clock on the generator line. Just alter the line frequency (gen speed) until they match up again each night at say 2 A.M. local. That's in the olde days....now I imagine computers handle it in real time.

awemawson:
Here in the UK  the number of cycles in a day in monitored and it is one grid parameter that is closely controlled, as you say, over 24 hours. I had a suite of Ferranti Argus 500 computers that I was responsible for at Park Street National Grid Control in London back in the '80's and '90's, that compared cycle count with a radio clock synchronised to a Swiss standard. I expect that they are long gone now - they moved control to Winersh in Berkshire, but will have something similar in whatever control system they are using nowadays.

John Hill:
Hi James, your enquiry has reminded me of a long forgotten project which never got past the pondering stage!

In my scheme which was for a clock to put on the top of the house (like the one on the local Post Office)  I considered using a windscreen wiper motor geared 60:1 to the minute hand of the clock face and of course a further 12:1 for the hour hand.

As you probably know a typical windscreen wiper motor has a worm driven wheel which carries a circular contact with a short break in it.  The motor is wired to run when the dashboard switch is 'on' in which position the motor will run regardless of the position of the circular contact but when the switch is turned 'off' the motor continues until the break in the contact ring is encountered (i.e. 'parks' the wipers).

In my scheme software on a PC would raise one of the modem control lines on a serial port once per minute for a fraction of a second,  the modem control line would control a 'solid state switch' which would take the place of the dashboard switch in the wiper motor circuit.

Not clever, no real electronics involved, but I did think it was a robust way of making a clock big enough to impress neighbours driving down the street.

Of course my software would check an on-line reference clock at intervals and one a year stop for a whole hour or go double speed to 'skip' an hour according to the requirements of daylight saving time.

Regarding solenoids, here is a thread where I experimented with an idea to make a 'long stroke' solenoid with power throughout the stroke rather than having all the force appearing near the end of the travel..

http://madmodder.net/index.php/topic,6119.msg65462/topicseen.html#msg65462

John

catceefer:
Thank you for all of your very helpful replies, which have given me plenty of food for thought. One thing that I had not realised before posting this question was just how much power would be required by the Arduino itself and the stepper motors. In my ignorance, I had envisaged a few AA batteries at the most.

John: I shall have a read of your solenoid thread. Years ago, I used to work on Strowger telephone equipment where we used slugged relays to delay either the activation or the release of the mechanism. The trouble is: it is thirty years ago now and I have forgotten most of what I learnt there. I could, though, put a small capacitor across the solenoid to give a slow release: that would at least take out some of the abrubtness of a solenoid-operated device.

Now to find a darkened corner in which to ponder and think.............

Thank you.

James.

John Hill:
James, the principle of my long stroke relay was to produce a magnet with a N pole at each end and a S pole in the middle!

The magnet is longer than the solenoid coil and the action is really the S pole moving back and forth within the coil being alternately attracted and repulsed by each end of the solenoid.

John

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