2 ms·
that all makes sense but i think if you're aiming for longevity then separating the active mechanical bits (mtbf low) from the electronic bits (mtbf high) is a
by contingencies 2y ago
that all makes sense but i think if you're aiming for longevity then separating the active mechanical bits (mtbf low) from the electronic bits (mtbf high) is a good idea, just because physical effort in proximity to breakable things is likely to break them faster. this would be a case for not building in the pullstring and instead using an external pump. but you could have both, as well. supercaps are good for capturing fleeting charge but don't store for too long. they do store longer than regular caps, but they leak current over time. an air tank can be 'on board' with high longevity and low mtbf. the connections/seals the probable locus of problems.
- kragen 2y agoyeah, i guess i don't really know how long-lived supercaps are. just as a rule of thumb i figure that they'll probably fail soon just because they're full of liquid, but that's not an infallible rule; maybe they're long-lived a 10-farad supercap at 2.7 volts could hold 36 joules and would still fit in your pocket, so you could totally charge it up with a pullstring. https://www.digikey.com/en/products/detail/tecate-group/TPL-10-10X30F/9930253 https://www.digikey.com/en/products/detail/tecate-group/TPL-... is 10mm diameter, 31.5mm long, and it's rated for 1000 hours of life at 85°. the datasheet projects that at 25° it will last 10 years with ±30% capacitance change and no more than 2× increase in esr. 53 years is 465000 hours but maybe at a low temperature and low voltage it would last that long? maybe it'll be 32× increase in esr but not a problem?
- contingencies 2y agoYou could ensure low temperature by encasing them in solid aluminium with a thin intermediate layer of thermal gel.