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I'm coming from a product design background and have very modest knowledge about electrical engineering. Please bear with me...

I'm currently drawing a small wearable device and have been looking for a physical (un)latching mechanism. The mechanism does not need to be particularly fast (<1 s), strong (<1 N), nor have a large displacement (~1 mm). The mechanism will be unlocking an object within a bracelet, and will do so rarely - probably just once.

However, the component needs to be quite small (ideal max height ~6 mm), off the shelf (manufacturing aim between 1000 and 5000 units), and be confined to the limited voltage and current from the batteries on wearable things (battery not yet defined).

I've looked at miniature solenoids, geared motors, piezo stuff. But, I feel like there's some component or clever solution I'm missing..?

(I acknowledge this as a kinda non-specific question, but it's sort of a blue pill | red pill decision at this point of development.)

EDIT: adding simple sketch of desired functionality simple sketch of desired functionality

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  • $\begingroup$ This needs a bit more context for a useful answer specifically what is the functional reason that it needs to be locked and unlocked for example is this a security or tamper evidence application or does it need to detach something in specific circumstances. $\endgroup$
    – Chris Johns
    Commented Mar 14, 2016 at 1:17
  • $\begingroup$ Thanks for the feedback Chris! It's not really a security feature, it's more a sort of unlocking a token. A little prize if you'd like. I'm considering using a spring loaded SD card slot to house the token, which means the user would be able to pop it out and in again. But only after it's unlocked. Did that make any sense? (also added a simple sketch) $\endgroup$
    – user5458
    Commented Mar 14, 2016 at 9:04
  • $\begingroup$ @CarlRasmus Do you want the receiver to eject the other component or just release the lock and then you can pull the two apart? $\endgroup$
    – GisMofx
    Commented Mar 16, 2016 at 2:35
  • $\begingroup$ @GisMofx It would be nice to eject at the same time, but I figured it would be too complex for this project. So yeah, main objective is just to release the lock and then the user can pull the two pieces apart. $\endgroup$
    – user5458
    Commented Mar 16, 2016 at 9:16

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If I understand correctly; you would like component A to detach from component B. Should component A be held in place mechanically and trigger a signal or become a circuit-interrupt when detached? If so, you should research micro-witches. They can be configured for "normally open" or "normally closed" when purchased. Another idea would be to place conductive material on component A so that it acts as a "fuse" when detached.

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  • $\begingroup$ Thanks for the response Mark, and sorry for being unclear. The desired functionality is that component A (latch in body) is mechanically attached to component B (token). Upon a non-physical external event, the IC would signal component A to unlatch and thereby mechanically release B. Component B isn't really intended as part of the circuitry, but instead an inert physical object, so I'm not sure your suggestion with micro-switches would work(?). However, I quite like your idea of the token (B) working as a fuse, and it could work as a nice little backup plan! $\endgroup$
    – user5458
    Commented Mar 15, 2016 at 19:36

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