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I have a motion activated circuit build with a spring switch (sw‑18020p) and powered by a CR2030 coin cell. Every time i "shake" the circuit, it turns ON for some seconds to grab some sensors readings and then turns OFF. Everything is insulated with epoxy so i don't have access to the components after i install battery.

I'm looking for some kind of circuitry to prevent the device to turn ON, like for storing purpose. I was thinking of a reed switch inside and a magnet outside, so if i remove magnet it operate normally and if i put magnet back, i could store it without activating by accident. The problem with reed switch is they are made of glass and break very easy, so i was looking for something more robust.

Anyone have a better idea?

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    \$\begingroup\$ Having encapsulated the reed sw in epoxy, is it really still all that fragile? \$\endgroup\$
    – user16324
    Mar 2, 2020 at 17:48
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    \$\begingroup\$ I think you'll find the reed switches surprising tough. I agree with Brian that once potted they are unlikely to suffer. Your going to need NC type which aren't as common. \$\endgroup\$
    – Transistor
    Mar 2, 2020 at 17:50
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    \$\begingroup\$ What about a micro power hall sensor/switch? \$\endgroup\$ Mar 2, 2020 at 17:50
  • \$\begingroup\$ Stefan: good point, it seems more robust than reed switch. I'm going to make a test to see if it works \$\endgroup\$
    – Geologic
    Mar 4, 2020 at 11:52

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reed switches require precise alignment of the electrodes for correct operation glass is an ideal matrerial as is it rigid, non-coductive, and non-magnetic.

If embedding in epoxy does not harden the reed switch enough (they are pretty tough to start with) pad the reed switch by placing it inside a tube of silicone before encapsulating it.

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  • \$\begingroup\$ Well, i have to make a test to see if is tough enough. I'll also try hall sensor to see if works. Thanks guys for the help. \$\endgroup\$
    – Geologic
    Mar 4, 2020 at 11:55

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