SparkFun Forums

[TheatreTech]

I have been tasked with making a spinning clock for an upcoming show. It does not have to function during the show except to advance to the next position during transitions. In my head a stepper is the best way to do this and just create a "next" button to cycle through the positions. Does any one have a nifty trick for taking control of the clock? And for the tricky part there are supposed to be 4 next to each other. Would it be better to have 1 stepper per clock or connect them mechanically?

Any input is greatly appreciated!

-Alex

[Mee_n_Mac]

By "spinning clock" do you mean an analog clock with hands for the hours and minutes and perhaps seconds ? Do the hands have to spin fast to simulate the passage of time or can the hands just advance to the next time/position regardless that the minute (? and seconds ?) hand(s) won't act like a true clock hands would ? Do you have to be able to stop at any time or just a few, well known in advance, positions ? How long do you have to move from one position to the next ? (Do you even need a motor ?)

Hard to say whether it would be better to link them all mechanically or just have them controlled individually but my inclination is to do the latter as it would be easier for me to do that rather than have linkages made. Size and spacing of the clock faces would play into this decision.

[macegr]

If the audience is not going to see the clocks moving, then having someone physically walk up and move the hands would probably be the most fail-safe method. The stepper motor doesn't care if it gets yelled at for not doing its job

[TheatreTech]

There are preset times known in advance. Motor is the way to go because there are sever other shows happening at the same time and having something be plugged in and push a button is much more reliable than in experienced crew hooking up a mechanical system daily.

The clocks do not have to function other than to spin to show passage of time.

[Philba]

yeah, stepper makes a lot of sense. The arduino (or other controller) would simply send out the right number of steps for each phase of the play. Do you have the actual clock mechanism? I assume you need hours and minutes so you can't just drive a hand directly from the stepper. It might be tricky to drive a clock mechanism directly. How you would do it is one of those "it depends" answers. I suspect mechanical linkage of multiple clocks is very tricky - better to have separate steppers. You need separate stepper drivers but can use one control signal if they are all slaved together.

You might want to have a rewind or reset function with some way for the controller to tell it's in the starting position. There are several ways to sense that the clock hands are in the right place. I like the idea of magnets and hall effect sensors.

Make sure you get arcade style buttons (big, sturdy). Debounce the crap out of them because you don't want glitches in the middle of a show.

[TheatreTech]

I was playing with a clock we have laying around and it looks like the set dial on the back of the movement has a hollow 1/8" tube. I was thinking just drilling the back open and inserting an 1/8" shaft.

The part I left out is that since they system has to be setup and removed daily it would all be built onto a box of some kind. If I did go with 4 steppers rather than chain & sprocket, I would be going with the EasyDriver. Could I just run 4 wires out of the arduino to each of the DIR, STEP. & GND pins on the EasyDriver?

[Philba]

yeah, that should work just fine. though it assumes that each clock mechanism is exactly the same.