I have a battery operated device which needs to be temperature enabled. Once the temperature goes above 60C, the device should start operation. Ideally it'll be like a fuse, and will continue even if the temperature drops below 60C after initial activation.
The device has a microcontroller, so I currently plan to put it into deep sleep and wake it to check the temperature every minute or so, however this will consume almost a microamp of current continuously (to operate the timer needed to wake).
I'd like to reduce that even further. I'm not aware of any circuit elements that could accomplish this, though, and any circuit designs appear to consume more power. Further complicating matters is that I have less than 32mm^3 volume available for any additional components to implement this.
I'm imagining a piece of wax separating two sprung contacts, but I don't want to develop something myself, I'm hoping such a device already exists at this tiny size.
Are there other options I can consider?
Best Answer
A bimetallic switch seems a likely candidate, that consumes no power:
Another fuse-like option is one made of Wood's metal. Standard alloy melts at 70 C, perhaps a different alloy melts at 60 C. Would operate once-only.