NC (Normally Closed) Reed Switch

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jake18
 
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NC (Normally Closed) Reed Switch

Post by jake18 »

Hi I am looking to include a normally closed reed switch in a project and was wondering if anyone could provide some tips on the best way to do this? I want my device to turn on when taken away from a magnet, and turn off when near the magnet.

Thanks!

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kcl1s
 
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Re: NC (Normally Closed) Reed Switch

Post by kcl1s »

Not clear what you are asking? It looks like Adafruit on sells NO reed switches but you can buy NC reed switches elsewhere. Most are only rated for 0.5 amp so if you need more power you will need additional components. Maybe a better explanation will help us understand your need.

Keith

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jake18
 
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Re: NC (Normally Closed) Reed Switch

Post by jake18 »

Thanks for the reply Keith.

I have seen a limited number of NC reed switches online, but I have read things that made me suspicious of whether they would really work. I was hoping someone with some experience using an NC reed switch on a project would mind providing some pointers.

Thanks!

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jake18
 
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Re: NC (Normally Closed) Reed Switch

Post by jake18 »

Also - would I be able to use a NO reed switch and just include a magnet in my project casing, and then open it (deactivating my device) with an additional magnet?

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adafruit_support_mike
 
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Re: NC (Normally Closed) Reed Switch

Post by adafruit_support_mike »

It depends on the amount of power you're trying to control. Most reed relays are used for signal connections, and can't handle a lot of current.

If you want to control more than 100mA or so, it will probably be most effective to use the reed relay to control power mosfets or the coil of a more powerful relay.

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jake18
 
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Re: NC (Normally Closed) Reed Switch

Post by jake18 »

Thanks for the response Mike. Unfortunately, as a beginner, I am unclear about several of the components of your post.

I am trying to use the reed switch to activate & deactivate an esp32 board. Is this feasible? And if not, what would be the best way to do this?

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adafruit_support_mike
 
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Re: NC (Normally Closed) Reed Switch

Post by adafruit_support_mike »

Yes, it can be done. There are several options depending on how much current the circuit is using.

Do you want to control power to anything other than the ESP32?

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jake18
 
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Re: NC (Normally Closed) Reed Switch

Post by jake18 »

The esp32 will be connected to an LCD

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DaBo
 
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Re: NC (Normally Closed) Reed Switch

Post by DaBo »

Just to weigh in here.

I have used reed switches before. They are quite common on pneumatic cylinders to read position of the cylinder (extended or retracted for example).

Festo was one company that I used to get pneumatic components from. If you check them out they should have reliable reed switches in many configurations. I'm sure there are other manufacturers that will be less expensive but I have always liked Festo's quality.

Dan

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adafruit_support_mike
 
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Re: NC (Normally Closed) Reed Switch

Post by adafruit_support_mike »

The ESP32 uses about 200mA while active, and an LCD will add about another 20mA, so we can estimate the current consumption at about 250mA.

There are plenty of normally-open reed switches at Mouser and Digikey that will handle 250mA without any trouble. You can put the switch in the positive wire between the battery and the ESP32.

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jake18
 
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Re: NC (Normally Closed) Reed Switch

Post by jake18 »

Mike - Do you have a recommendation for where to purchase a normally-closed reed switch that will work for my project?

DaBo - Will those that you mentioned work with my esp32 and LCD setup?

Thanks guys

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jake18
 
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Re: NC (Normally Closed) Reed Switch

Post by jake18 »

This one will work right?

https://www.mouser.com/ProductDetail/St ... 64qA%3d%3d

Any clue how to connect this specific model to the esp32 and battery?

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adafruit_support_mike
 
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Re: NC (Normally Closed) Reed Switch

Post by adafruit_support_mike »

That one would work, but is a double-throw switch.. it swaps the connection between two different lines.

What you’re looking for is a single-pole normally-open switch, which Mouser also has:

https://www.mouser.com/Electromechanica ... ricing%7C0

The least expensive one is here:

https://www.mouser.com/productdetail/ha ... tBicgF0%3D

and will simply go inline between the battery’s positive terminal and the rest of your circuit.

Hamlin/Littlefuse has an excellent reputation, so you can be comfortable that it’s a well-made switch.

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jake18
 
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Re: NC (Normally Closed) Reed Switch

Post by jake18 »

I'm looking for my esp32 to turn off in the presence of the magnet, and turn on when taken away from the magnet.

I thought what I needed was a normally closed switch?

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adafruit_support_mike
 
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Re: NC (Normally Closed) Reed Switch

Post by adafruit_support_mike »


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