motion switch

Dec 13, 2010 8 Replies
A

I'm looking for a mechanical switch that responds to centrifugal force by closing a NO contact. I need to switch 20mA in a space of about 5mm in diameter and 8mm long. It also needs to be self-contained (no assemblies of several other parts) since it's going to spin pretty quickly and be in a small space.



This is for somewhat ridiculous flashing LEDs at the end of a RC helicopter's balance bar.



Anyone have any keywords or parts in mind?



(A microswitch with a small mass pressing on the switch that actuates when I spin up might be doable if there's no other way.)


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M

mercury switch?

How are you powering the leds? If the battery is spinning too, use its mass to short against a contact.

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D

I've seen this done using a verticle compression spring (ie mounted on its end - soldered to PCB) with a vertical wire up inside the spring (also mounted to the PCB) under rotation the vertical spring bends sideways and touches the centre wire. Used in toys.

Clunky ascii art......

idle:

| O | O O | O O | O O | O O | O O | O O | O O | O O | O O | O

-------------

-------------

operated:

| O| O O | O O | O O | O O | O O | O O | O O | O O | O O | O

-------------

-------------

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R

Some of the "tac" switches may do the job by gluing a small mass on the button.

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T

Allelectronics.com has had some 'Exercise Counters' (/Pedometers) which have a mercury switch as part of the assembly. This may be helpful for your requirement.

TomC

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A

Sure, and the first crash you spray out mercury from a 6000RPM rotor.

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A

s

That's what's in there now. The problem is that it only works in a narrow range of RPM. I guess the spring must vibrate in different modes or whatever. I think I'll just skip this for now.

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G

ce

mm

s

its

nd

Hmm, then it sounds like it might be a matter of finding the right spring. You've got some constraints, what can you vary?

George H.

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E

Spring (not shown) pushes nailhead toward left in the diagram.

|| ---Tube--- ||====Nail====> #

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