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I'm currently working on an electronic design who need to be turned on just once and continue to run until the battery die. I was searching for a way to do that and the most obvious was to use a plastic strip who act like a "remove before flight" lock. A lot of toys and small consumer products use that but I didn't found any specific component which can allow that.

I know that on most of these devices, a plastic strip in inserted before the battery to prevent electrical connection between the circuit and the anode or cathode. But I would like to know if there is a component which could allow that without putting it on the battery. Since my design could make the initial launch very unpractical due to the position of the battery.


I will reply the first three comments:

  1. the product is shipped with the battery already inserted. Due to confidentiality reason, the final custommer don't have to access the device.
  2. Nice idea. Unfortunately, my geometrical limitations will probably not allow that. But I will study it.
  3. It's the only way for me to control that the system is launched only when really used by the final custommer. Long time stocking of the full product could impact the battery life during normal use.
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    \$\begingroup\$ Why can't the act of inserting a battery do this? \$\endgroup\$ Sep 24, 2018 at 8:14
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    \$\begingroup\$ You know how battery contacts are a bit springy? Well, forgetting the battery part, if you had two back-to-back with that bit of pull-out plastic between them, that would work. If you're getting lots made, you could probably get better-shaped springy metal. \$\endgroup\$ Sep 24, 2018 at 8:15
  • \$\begingroup\$ Do you wish this to be a safety device to prevent accidental triggering or to be the device that actually launches your drone or thingy? \$\endgroup\$
    – K H
    Sep 24, 2018 at 8:21
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    \$\begingroup\$ Why “geometric limitations”? All you need is a small slot with the tag sticking out and it will work... \$\endgroup\$
    – Solar Mike
    Sep 24, 2018 at 8:28
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    \$\begingroup\$ @Arsenal It could even be a fake button that pushes a PCB jumper link onto pins. \$\endgroup\$ Sep 24, 2018 at 14:09

4 Answers 4

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You could use two PCB-mounted spring battery terminals mounted next to each other, so that the spring terminals are pressing together. They would probably have to be hand-soldered as they will try to push each other out of the board during soldering. Then add the plastic strip during manufacture, after testing but before assembly of the case.

For example, the Keystone 590.

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  • \$\begingroup\$ This is very clever, but isn't it going to just be the worst thing to solder ever? \$\endgroup\$ Mar 6, 2019 at 23:22
  • \$\begingroup\$ @AndrewMacrae I'm sure it's not the worst. You could solder one in place. Then jam in the other, using a heat resistant tool, and hand solder it. \$\endgroup\$
    – Simon B
    Mar 6, 2019 at 23:26
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Some smoke detectors with built in batteries have a one way catch, latch or clip that is used for a disable button. Once you slide it to the off position, plastic of the casing is used to prevent the user from sliding it back without damaging force or deconstruction. This is coupled with a switch.

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How about just a simple slide switch? Put a pulltab on the slide so it can only be pulled to the on side.

https://www.digikey.com/products/en/switches/slide-switches/213?FV=ffe000d5%2C1f140000&quantity=0&ColumnSort=1000011&page=1&stock=1&k=slide+switch&pageSize=25&pkeyword=slide+switch

I guess that it's similar to the PCB jumper onto pins idea, but perhaps a little more mechanically secure.

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A strip of paper between two neodymium magnets would achieve this - connections can be soldered to the other sides and the magnets would not need to be very big if weight is an issue. A stiff strip and magnets with beveled edges would allow the strip to be re-inserted easily

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  • \$\begingroup\$ Note that applying excessive heat to magnets affects their performance. \$\endgroup\$
    – Daniel
    Sep 24, 2018 at 19:08

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