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I have an electromagnet-based SPDT relay that I am considering using inside a model rocket. It is estimated to experience between 10-20G of acceleration.

Should I worry about the acceleration overpowering the electromagnet? I could use a solid-state relay, but I don't have any handy and would have to wait for shipping.

For context, I am using the relay to discharge capacitors (in parallel) into an electric match to set off a second-stage motor. An Arduino Nano will be used to control ignition.

Relay failure could result in the parachute not deploying (out of the second stage), or even the second stage going off before the first motor disconnects from the body.

EE is not my background (better with CS, but still crap at both). I have researched enough to have a decent understanding of the peripherals needed to launch rockets.

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  • \$\begingroup\$ Yes you should worry. Is an SSR an option? \$\endgroup\$ – The Photon May 2 '18 at 18:55
  • \$\begingroup\$ The question should be titled "Electromagnetic relay under high acceleration". Gravity ('g') has little to do with it. 'G' is usually the universal constant of gravitation. \$\endgroup\$ – Transistor May 2 '18 at 18:55
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    \$\begingroup\$ @Transistor, The "gee" is a fairly common unit of accelleration when speccing shock and vibration reliability. \$\endgroup\$ – The Photon May 2 '18 at 18:56
  • \$\begingroup\$ @ThePhoton with shipping, it is. I wanted to see if I could use relays I had lying around. \$\endgroup\$ – Phil May 4 '18 at 1:43
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An appropriate relay for your application will have a specification for shock and vibration reliability. For example, here's the spec from a particular automotive-rated relay I found:

enter image description here

Notice that the spec doesn't promise absolutely no change in contact status, only that (per note 7) it won't make or break contact for more than 10 us at a time due to the specified shock and vibration. So you may need to design your circuit to allow for brief relay faults.

Given these issues, it may be easier to design with a solid state part than with a relay.

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  • \$\begingroup\$ Seems like I will us an SSR - the relays I've found can take 100G shock (no worry there), but it's not clear if it doesn't switch at all under high acceleration. I can't take risks with the second stage going off with any little amount of energy. \$\endgroup\$ – Phil May 4 '18 at 1:41

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