Hey Everyone,
I am building a clock with 2 stepper motors that will allow the hands to move independently and go fast or slow on the top of the hour. Then once the clocks are done doing their show, I want to return them back to the correct time. Since the clock hands could be anywhere on the dial when I stop I need a way to reset them to a known position. My thought was to use a Hall Effect sensor embedded in the face and then put magnets on the hands. The problem that I have is the sensor is not sensitive enough (A3144) and it never sees the hands. Does anyone have any suggestions on how to improve the sensor or to do the hand detection some other way?
Thanks in advance, you guys are the best!
Jeff
jefflundstrom:
Since the clock hands could be anywhere on the dial when I stop.
Is this true? If you are using a stepper motor, I think the hands should not be anywhere on the dial, they should be where they step them to.
Hey Nick, Thanks for the reply. When I move the hands in a pattern I will know where they are, but if the clock loses power I will not. I want to be able to make sure the clock is always at the right time, every hour regardless of power.
If the hands are in arbitrary positions (like at power on) the only option is to "home" them.
Usually, the home position is sensed with an optointerruptor or switch. Then you keep track from there. The sensor does not have to detect the actual hand -- it could detect the slot in a slotted wheel attached to the stepper motor shaft.
That is a great idea, I like the slot detect instead of having the face have a sensor in it. Thanks!