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Inrush current limiting resistor size? Answered

I am building an application where LED strip lights will be powered off a 12V DC battery and switched on and off using a magnetic reed switch. I've been finding that the reed switch often fails to turn off when the magnet is removed. Searching on the net suggests this is because the contacts are getting fused by a large inrush current and the suggested fix is to wire a resistor in series to prevent this - so far so good but I cannot find anywhere guidance on the rating of the resistor I should use - at least guidance I can understand - as far as I can tell a resistor as low as 1 ohm may be required but not sure if I have got this correct - anyone know? Thanks

Discussions

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verence

3 years ago

Reed switches are not really to be used as switches, treat them as a sensor.

Use the reed switch to control a relay or a transistor driver stage.

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iceng

3 years ago

If you have a large capacitor to stabilize the capacitor then your concern mat be legitimate about the switch.

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icengiceng

Answer 3 years ago

A rare SPDT reed switch handling 20ma

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icengiceng

Answer 3 years ago

You should know that some reed switches carry current and are sensitive enough to hold themselves closed due to rotary flux field around the conductor. And there are mercury whetted reed switches...

Glass_Reed_Switch_Reed_Switch_Magnetic_reed.jpg
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Nighter3D

3 years ago

As mentioned below. Reed switches are more of a sensor then a Switch that can send a lot of current. They are best used to triger other "Load switch" parts like Relays, Power-Mosfets and so on.

Led-strips can be quite demanding in current so it is quite possible you are overloading the Reed-switch (most generic reeds are rated for ~250mA) which can cause trouble.

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Downunder35m

3 years ago

You don't use reed switches to actually switch things requiring power.
And what would be the point of the resistor? It will make your LED's go dim - there is no inrush current for LED's as they not an inductive load.