Anyone ever try to modify one of those cheap battery operated analog clock mechanisms as gear train? It would make an extremely lightweight gearbox for small bot.
Some quick research on the web provided some insight on how these things work:
http://www.explainthatstuff.com/quartzclockwatch.html
Then I tore open a broken clockwork that's been sitting around for ages. OK, I tore it open first, then did the research. ; j
The result? I was able to disassemble the mechanism, remove the coil, crystal and battery contacts, drill one small hole in the case, and I had a working lightweight gearbox. I inserted the cut off end of an electric toothbrush to propel the driven gear.
The exterior thumb wheel (originally used for settting the time) turned a bit slowly, but that was with a 3v motor. I tried stopping the thumb wheel with moderate pressure from my finger, and I couldn't do it.
I did notice the clock hands (OK, just one hand. This is from a broken clock, remember?) didn't move with the motor. It turns when I move the thumb wheel by hand, so I'm not sure what's going on there. However, I think I proved to myself this is a workable approach.
https://www.youtube.com/watch?v=GP_4oVzAb2U
It’s encouraging to know
It’s encouraging to know someone else has tried this. Thanks for the advice. I gutted mine, including the coil, so I’m dependent on an external motor. I just kept the magnet and small gear from the original stepper motor. I intend to mount that to the drive shaft of a small motor, so I can use standard motor control instead of a step motor.
If I understand you correctly, the reason you only get it to move one “tick” (or step) at a time is because that’s how stepper motors work. You have to apply voltage in the right sequence to the right pins to keep the motor rotating. Since you gutted the electronics but kept the whole stepper motor intact, you have to deal with that sequencing. I’m just using a piece of the original motor because it has the right gear size to drive the rest.
Someday I’ll grab two identical clock movements and use them for propulsion on a lightweight bot. I like the idea of a solar bot like you suggested.
Check the URL I posted in my
Check the URL I posted in my original message. I believe it is a very tiny stepper motor, at least in most cases. It’s a coil and magnet driven by electronics and the crystal for timing.
Gareth’s post makes me re-think about the possibilities of using the built in motor, with a faster clock speed and the built in driver circuit (it’s under a black blob of plastic). Or maybe bypassing the circuit but keeping the stepper motor and just adding a stepper control circuit to drive the motor forwards/backwards/breaking. As long as you are talking about a feather weight robot, this mini-stepper could be up to the task. Push it too hard or fast and I’m not surprised if it overheats as Gareth noticed.
Making time fly
As Gareth proved with his experiment, time can move very slowly… even at 10x normal. Using the minute hand the driven wheel will obviously move at 1 rpm (or 10 rpm with his coding acceleration). So how can we speed this up for a more practical bot?
That could be the basis for the challenge. How fast can you make “Time Fly”? A restriction on the challenge would be using the original mini stepper from the clockwork. There would be few other restrictions.
A few techniques for speeding come to mind:
- Additional gearing (trading off torque for more speed)
- Faster clocking (perhaps with an external clock if the uController’s onboard is too slow)
- Gigantic weightless wheels so that 1 rpm provides decent travel (not practical, but my personal favorite)
I haven’t issued a challenge yet. I’ll have to review what the guidance is on issuing one. Anyone please feel free to submit your comments or ideas for this challenge.
What would people like as a prize? I’d like more TIME. ; j
