Bottle opener counter

Discussion in 'The Projects Forum' started by frusciante89, Nov 13, 2012.

  1. frusciante89

    Thread Starter New Member

    Nov 13, 2012
    Hi guys, I'm new! My name is andrea and I study mechanical engineering at UCI. I'm building a bottle opener with a 3d printer and I was thinking of adding a nice feature. I saw this:

    Do you have any idea of how to build the circuit (maybe they are using a strain gauge?)? Is it simple? And how small can I make it?

    Thanks for your help
  2. wayneh


    Sep 9, 2010
    I think that's a lot like one of those cheap pedometers, in the sense that it just counts makes-breaks. It uses a magnet to detect coming near a cap.

    So, it could be quite small.
  3. Markd77

    Senior Member

    Sep 7, 2009
    I've got one of those. It's even simpler than magnetic detection, see how the metal opening part is in two parts? It just measures continuity, so just like a switch.
  4. elec_mech

    Senior Member

    Nov 12, 2008
    Welcome to AAC - happy to see another ME here. :D

    You could make this with a handful of parts, but it would probably take up more space than a standard handle could hold unless you use SMT (very tiny) parts. Another idea is to program a microcontroller, but you'd still want an SMT version. Soldering and mounting such a small display will also be a challenge. This is not to discourage you in the least, just some things to keep in mind.

    For this application, I would suggest a cheap pedometer as wayneh mentioned. You can often get them at the Dollar Tree for a buck. They are small, cheap, and will save you a lot of time.

    If you take it apart, you'll find a simple switch that causes the pedometer to counter everytime it bounces. You can remove the switch and you'll be left with two contacts/wires.

    If your bottle opener's teeth are metal and you can physically separate it so there are two halves, you can connect one of each of the wires to each of the teeth. In this way, when the bottle opener's teeth contact the bottle top, continuity is established (like pushing a button), and the counter will count.

    This may not work as reliably as the item you posted a link to because of mechanical bounce, i.e., the counter may count multiple times while pulling the lid off one bottle, but we may be able to help you with that too.

    We're happy to provide a schematic for building a circuit if you'd still like to make this yourself, but for the size requirements, hacking a pedometer is probably your best bet.

    Hope this helps.
  5. wayneh


    Sep 9, 2010
    I suspected as much, but the link described it as magnetic. Anyway, continuity is even easier. It must have debounce programming to prevent multiple rapid hits.