The Shop > Electronics & IC Programing

Stepper Motor Control

<< < (2/5) > >>

raynerd:
...and just to add my two penneth to the functionality of the concept -. It won't keep time at all!! :-) I made a binary clock many years ago using a pic with a crystal 32768hz oscillator, even my code was causing the time to go out badly with no moving parts, just Leds! Good luck and hope you prove me wrong. It'll certainly look smart.

vtsteam:
Well that's a little easier to talk about, but still no specifics........

"The copper dragon is still ongoing, the clock being planned for its completion. "

still doesn't say how big this clock (or dragon -if it is being moved by the clock) -- is.

An R/C servo (and I've used alot of them) might not last very long under continuous use in a clock. They've got tiny potentiometers in them, and 100 hours flight time per year would be heavy usefor them.

As one possibility, If you're going with a motor anyway, why not consider a synchronous motor? You do have to reset the clock if the power goes out, but otherwise they will keep good time because the power line is adjusted in frequency to do just that. They were actually used in electric clocks and clock radios. Those were meant for continuous use over long periods of time.

You could use a cam to provide some pretty complex movements for your figure -- and easily adjustable timing fairly simply. Think of the amazing cam drives on automatons that were traditionally used. This would be very simple compared to those. And it is a mechanism in sync with the history of clockwork.

catceefer:
Thank you all for the advice, which has given me plenty of food for thought.

Raynerd: thank you for the sample code, which makes perfect sense. I shall have to have a little think, though, if your experience showed that it is difficult to get it to keep time.

Vtstream: a little more context. The dragon, which is about 6' long and 3' 6" tall, is a totally separate, static project. I am nowhere near a final decision, but I envisage this clock to be a large wall clock for indoor use in a house. Even though I only wish to pulse the mechanism once per minute, it does sound like a servo could give up the ghost after a month or so of use. I shall have a think about synchronous motors or, perhaps, traditional clockwork after all.

Regards,

James.

vtsteam:
Just a mention re. single board computers keeping good time.....  For this kind of task there's usually a Real Time Clock (RTC) circuit in more complex boards, or in a peripheral. A small computer board could function as a clock movement controller, but it may take special interrupt programming and possibly off-loading tasks to specialized components rather than having a single processor try to do everything.

I think the physical bulk of what's needed to do it, besides the programming and electronic issues would argue in favor of a synchronous motor and cam. On the one hand you have just a mains suitable motor, on the other, a stepper motor, a stepper driver, a stepper power supply, a single board computer and any auxiliary controls (buttons, display, etc.) you think necessary, plus lots of wiring.

However, there's one great argument for a computer/stepper version: if you want to dig into digital electronics and programming to learn more about it. Or if it just simply appeals to you! If that's part of the equation, sounds like it would be an instructive and interesting project.  :thumbup:

philf:
I think a single board computer and stepper drivers is overkill for this application.

The video you linked shows the clock working very much like a slave clock for a master clock. These are nearly always driven by a solenoid which as you point out is abrupt and noisy.

I agree with Steve that the simplest solution would be to use a 1 rpm synchronous motor and design a cam to give the required movement over a fraction of one revolution.

The mains frequency is fairly tightly controlled and I believe over a 24 hour period is very good.

One of my master clocks always keeps the main spring permanently wound up by a cam on a 2 rpm synchronous motor.

Cheers.

Phil.

Navigation

[0] Message Index

[#] Next page

[*] Previous page