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Does anyone know how to use a normally-open reed switch in a way that is "normally-closed"?

I have a device that needs a reed switch attached to its power source. This is because when it is stored in its storage container, it is meant to open the circuit to not powered ON, and as soon as you take it out of the container, it should close the circuit and power ON. (Note: the container has a magnet attached.)

The problem is that I can't seem to find any NC reed switches I can use. I'm looking for something small with two terminals like this.

If anyone knows where I can get them from, feel free to send me a link. If not, how would I go about using a NO switch as NC?

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  • \$\begingroup\$ It really depends on what exactly is the circuit behind your reed switch. You could do this with a pullup resistor for example but it's hard to tell without further details. \$\endgroup\$
    – Tioneb
    Jan 25 at 9:16
  • \$\begingroup\$ This datasheet lists NC. \$\endgroup\$ Jan 25 at 9:24

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It is possible to convert a Normally Open reed switch to a Normally Closed one.

This is done by adding a bias magnet. A permanent magnet is placed so that it closes the relay, and then the actuating magnet or electromagnet will have it's polarity such that it cancels the magnetic field of the bias magnet. See this document.

Of course this then gets you into the realm of magnetics and finding the right strength of bias and actuating magnets to make it work reliably.

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The reed switches you want to use do exist, so there is no need for converting an NO switch to an NC switch (unless you really want to).

Product recommendations are not done here, but you may want to search a larger component supplier for SPDT reed switches, using this Mouser query, for example, or this Digikey query, for DT and NC reed switches.

You will find plenty of reed switches for your purpose.

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