Speculative - sensing rotations, can't use rotary encoder

Hi,

Apologies if this topic irks anyone.

I’m trying to detect when someone churn a butter churn, but I won’t be able to attach a rotary encoder to the axle that it turns on. Does anyone have any ideas on how this could be done?

What I was trying to do was attach an Arduino with an accelerometer to the thing that rotates around, but this isn’t working. You can see where I placed the Arduino in the photo
Imgur

Maybe I should be using a gyro instead?
I tried using a tilt switch; if the switch has been turned on 20 times in the last second, then some one has been churning it, etc.

Any ideas? All help appreciated.

Martin

Edit - correctly attached the photo

You can attach photos you know, rather than sending people off to an image-sharing site.

How to use this forum

Can't you attach a magnet to the churn and have a hall-effect sensor adjacent to see if the magnet passes it?

Hi Nick,

Yes, I tried to embed the image in the post but it didn't work for me. Does it work with imgur?

I never though of using a hall-effect sensor. I'll give it a shot when I get my hands on one. Is there any way that the accelerometer would work, do you think?

Look at the link. You upload the file from your desktop.

martin_cork: I never though of using a hall-effect sensor. I'll give it a shot when I get my hands on one. Is there any way that the accelerometer would work, do you think?

How would you connect to it? With the sensor the only thing that moves is the magnet. Or maybe have some light detection system. For example, if the churn is in a fixed location (which it would need to be anyway for the magnet) then you could attach (or paint) a black/white pattern on the rear of the churn (out of sight) and detect with a photo sensor if the light level changes (which it would if it was turning).

martin_cork:
Yes, I tried to embed the image in the post but it didn’t work for me. Does it work with imgur?

It is a really good idea to scale your images to 1000 pixels are less so they can easily be seen.

Ok. I just used the tag...I do it properly in future, I promise!

Thanks Nick, you've given me pxBeey of food for thought. I was going to connect them using xBee. The magnet + hall-effect sensor sounds like it could be the best option. I'll look around for a type of flick switch that the rudders could tip off on each rotation, if such a thing exists.

What packaging constraints do you have? The mechanism seems pretty accessible and it looks as if it ought to be easy to fit a proximity sensor, or just a cam/switch arrangement. If you want better resolution, you could use the shaft as an optical encoder by putting light/dark stripes on it, and putting the optical sensor on the stationary body.

If you just want rotation detection not rpm count. Mounting some steel flag on some rotating part and sensing it with an inductive sensor is the standard solution