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I have a gear that needs to have roughly one rotation per day. It does not have to be smooth or consistent. So far, the best I have come up with is to have a stepper motor with an arduino that sleeps, wakes up once an hour maybe and turns the stepper a little bit.

Which arduino should I use for this and is there perhaps a simpler method? Is there any way to fully cut power then when powered on the arduino advances the motor and then shuts off?

Any ideas?

I want to run off of a 9v battery and get as much time as possible.

edit: adding details as requested

the rotation needs to happen slowly over the 24 hour period. The tube being turned is a light plastic 1" diameter tube that weighs about 2 lbs.

James
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  • How big is the gear and how much torque does it need to deliver? Is the load active or static? Is it ok to sleep 24 hours or whatever and then do a whole rotation? Perhaps you should edit the question to answer the above questions, and also say something about the overall purpose and context. – James Waldby - jwpat7 Dec 04 '16 at 07:22
  • ok, edited to add details. – James Dec 04 '16 at 08:17
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    Using a 9V battery to power a motor that will rotate 2 lbs will probably not work as those batteries have too little energy. Also, sleeping an Arduino does not reduce its current consumption much (see my answer to a recent question: http://arduino.stackexchange.com/questions/31813/how-to-make-battery-last-for-months/31815#31815). – jfpoilpret Dec 04 '16 at 08:40

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Steppers require current - and power, due to I^2*R losses) to hold a position. Power off, they free-wheel. What kind of efficiency do you need? A stepper might not be the most power efficient.

An escapement permits or causes a gear to index one position and prevents it turning any farther. In a clock, it permits a weight-driven or spring-driven shaft to index. You'll probably want one that drives the shaft as well, probably with a solenoid.

Another option that comes to mind and doesn't need an Arduino, is a clock motor. Gear down the hour hand 2:1 and you're done. Find a 24-hour clock motor and even that gearing will have been done for you.

JRobert
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Turning of the stepper in between, will result in reduced holding torque. This might be a problem.

I'd suggest using a AA battery pack. 4 AA batteries will give you around 5V. The Arduino doesn't require a precise 5V, so you don't need a voltage regulator.

I'd suggest using something like a Arduino Pro Mini, or Arduino Micro, as those don't have USB-to-Serial chips on the board, using up power all the time. Remove the power led, and put the uC to sleep as much as possible.

If you want accurate timing, you'd want to add and RTC module.

Gerben
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