Detect Opened Bottle Cap

Hello! I'm building a smart bottle cap. Every time it's twist open it records a long timestamp to local storage. When user opens a smartphone app it syncs data from storage to phone via bluetooth LE. It is powered by button cell.

What would be the best low-power cost-effective way to detect when cap is twist open? I have the following sensors: http://amzn.com/B00CBDUD60

I was considering:

  • Potentiometer
  • Rotate Encode
  • Hall Sensor
  • Tilt/Mercury Sensor

Thanks!

zavidovych:
What would be the best low-power cost-effective way to detect when cap is twist open?

I guess you’re trying to measure twist of the cap relative to the bottle. What constraints do you have? For example, are you free to change the design of the cap to add a switch that is operated by the neck of the bottle when the cap is fitted?

PeterH: I guess you're trying to measure twist of the cap relative to the bottle. What constraints do you have? For example, are you free to change the design of the cap to add a switch that is operated by the neck of the bottle when the cap is fitted?

No constrains on cap shape. I'll be building electronics, then model and 3d-print a cap around it. Having all electronics on the cap is preferred so it can fit on any bottle. But if placing some electronics on the bottle itself would significantly reduce cost and power consumption, then I'll be building a custom bottle for the cap as well.

In that case I think the simplest solution would be to build a switch inside the cap which was operated by the neck of the bottle. You can use that switch to trigger whatever you want when the cap is removed from the bottle.

zavidovych: No constrains on cap shape. I'll be building electronics, then model and 3d-print a cap around it. Having all electronics on the cap is preferred so it can fit on any bottle.

Not all bottles have the same size neck and, even if they do, not the same thread.

PeterH:
In that case I think the simplest solution would be to build a switch inside the cap which was operated by the neck of the bottle. You can use that switch to trigger whatever you want when the cap is removed from the bottle.

That would make most sense economically, thanks.

Henry_Best:

zavidovych: No constrains on cap shape. I'll be building electronics, then model and 3d-print a cap around it. Having all electronics on the cap is preferred so it can fit on any bottle.

Not all bottles have the same size neck and, even if they do, not the same thread.

True, I guess I was hoping there's a most common standard used by most bottle makers. On the second thought this might not be the case, so I'll probably sell the cap along with a custom bottle.

You could put tinfoil on the cap like so:

____
| |       | |
   |     |

The bottom is the bottle, when it connects to the cap, it closes. You could use this to test if the bottle was open/closed, which might help a little too. It's dirt cheap too.

zavidovych:

Henry_Best:

zavidovych:
No constrains on cap shape. I’ll be building electronics, then model and 3d-print a cap around it. Having all electronics on the cap is preferred so it can fit on any bottle.

Not all bottles have the same size neck and, even if they do, not the same thread.

True, I guess I was hoping there’s a most common standard used by most bottle makers. On the second thought this might not be the case, so I’ll probably sell the cap along with a custom bottle.

You’ll also need to consider the contents of the bottle. I presume they’re for human consumption and, therefore, need to be kept apart from poisonous substances (lead and copper) and allergens (some people are allergic to gold or silver). Your best bet would be to bury all your components in food grade plastic, which only leaves you with the option of the hall effect sensor and magnet. I don’t know if the plastic used in 3D printing can be used with food. Check with the suppliers.