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eftychia at 05:05am on 2015-10-26Does anyone have an old, electric, analog alarm clock you no longer want? (It doesn't have to keep accurate time, have all its hands, or have a functioning alarm -- I just need a working clock motor. Actually, if there is something else wrong with it, I won't feel as bad about dismantling it.)
Why:
Like many other cats, Perrine enjoys watching, playing with, and drinking running water, and asks me to turn on the tap in the bathroom sink for her. I want a fountain for her. I have heard stories of the pumps in cat fountains and decorative fountains burning out after a cat drank the fountain dry. So I thought I'd try using an Archimedes screw because that looked resistant to that sort of problem[*] (and when I started reading up on them, that's one of the features that kept coming up, so I was right). So I need to make a screw and a support for it and attach those to a reservoir -- I plan to ask friends with 3D printers for help with that. Then I need a motor. I was going to use a small DC motor, reduction gearing or a belt, and a wall-wart to power it ... but I don't know how long one of those will run continuously.[**] So I started thinking about electric motors designed to handle continuous use for very long periods, and the only (small) 100%-duty-cycle motor that came to mind was a 1960s/1970s electric alarm clock.[***]. So: anybody got an old clock to get rid of?
(Yes, I know I don't need Another Project. This is an old project I've had a new idea on.)
[*] A float controlling a cut-off switch would also work, yes. If a whole pump of a suitable size falls into my hands, I'll go that way.
[**] Or I could use a proximity sensor, maybe a pressure switch under a mat, to turn the pump on only when Perrine comes near the fountain, but I think she'd react better to one that just runs all the time.
[***] No, I don't know whether it'll have enough torque. I hope so, since I don't have to move very much water, a 3D printed screw will have less mass (and be more effective) than the improvised screw I started trying to make, and an Archimedes screw pump turns relatively slowly. So even though the alarm clock motor is only built to be able to move clock hands around, I'm hoping it'll have enough extra oomph beyond that for me to get away with using it. This will be an experiment.
(no subject)
An industrial step motor would probably be built to even better standards. The drive circuit would be more complex, but not too bad. Junk printers or CD/DVD drives would have step motors.
(no subject)
I've never built anything using stepper motors. What's the learning curve like? (And would the motor from a printer or CD drive put up with continuous operation forcweeks at a time? Though I guess hard disks spin for ages at a stretch, and I think I have a few 100 MB drives that I could take apart. I'd need to gear down the speed a lot more on one of those, I think (but in turn, that means that sufficient torque wouldn't be something I'd need to even worry about, right?). I'll look at the hard disk pile tomorrow.)
(no subject)
A hard drive spin motor is certainly rated for continuous operation, but would need to be geared down a lot, I was thinking about the step motors used for head positioning on CD drives and some floppies.
I have an extra step motor driver board (they're cheap these days) that would just need a digital signal at the correct frequency. You can have it if you decide to go the step motor route. I can build up a circuit with a 555 IC to drive it. I may even have a step motor that I don't need.
(no subject)