What's this kind of button called...?

Hello,

i'm looking to build my own 'the door is open/the windows is open' notifier. I'm thinking there has to be a button with a single spring which, when released, will allow power to flow - a 'negative button', so to speak. This way, I could hook up a solution where my microcontroller 'boots' on power-on when a window that the button faces is opened.

There has to be a button like this - but I have no earthly idea what it's called. Can anyone help? Thanks in advance.

Hi,

what do you think about inductive or magnetic sensors? With a little metal plate you could see when the door/window isnt closed.

Basti

Micro switch?

HI,
Magnetic reed switch, magnet on the door or window, switch is held ON by the magnet being near the switch when the door is closed.
This way you will know if circuit is functioning in normal closed doors and window.
If circuit fails it will alarm just a if door or window open.

Tom.... :slight_smile:
for example

You are looking for a normally closed micro switch. These switches usually have a change over switch so you can wire it up normally open or normally closed.

I think you can get “press to break” switches as well as “press to make” switches.

However if it is connected to an Arduino you can use either and invert the sense of the switch with program logic.

And @Grumpy_Mike has reminded me that most microswitches have two contacts - one is normally closed (NC) and one is normally open (NO).

…R

Thanks everyone - especially you, @Grumpy_Mike! The reason I'd rather not go for a Magnetic reed switch is that I'd like these sensors to be batterypowered, and only use battery if the window or door is open, which they would usually not be 99% of the time. I don't care if it's closed, and with a magnetic reed switch I'd have to use battery to keep the device on and sense all the time. By sensing 'mechanically' I could have the device powered for years on a battery pack. Makes sense?

and with a magnetic reed switch I’d have to use battery to keep the device on and sense all the time.

No you can get reed change over switches as well.
Reed switch change over
And you can probably get them cheaper than that as well.

This is a normally closed sensor:-
normally closed reed switch

Grumpy_Mike:
No you can get reed change over switches as well.

A technique I have used (to create a submersible switch) is to place an ordinary cheap reed switch centrally between two small bar magnets, all three items aligned in parallel but not too close. The magnet polarities are arranged in opposite directions so there is little field in the vicinity of the reed switch. Moving one magnet away causes the switch to close.

Nevertheless using a microswitch as suggested by 'dannable' is probably the best option.

Grumpy_Mike:
No you can get reed change over switches as well.

Good stuff - I did not know this. Thanks for pointing it out.

Archibald:
A technique I have used (to create a submersible switch) is to ]...]

Thanks for sharing - this may come in handy for an especially 'cramped space' scenario that I have. Thanks a lot.

harleydk:
Hello,

i'm looking to build my own 'the door is open/the windows is open' notifier. I'm thinking there has to be a button with a single spring which, when released, will allow power to flow - a 'negative button', so to speak. This way, I could hook up a solution where my microcontroller 'boots' on power-on when a window that the button faces is opened.

There has to be a button like this - but I have no earthly idea what it's called. Can anyone help? Thanks in advance.

if you look at door switches, they have a very simple magnet on the door and a reed on the frame. when the door closes, the magnets change the state of the switch. if your case, it seems you want normally open.
since your 'normal' state is the door is closed and the magnet is holding the switch in position, you want it open.
others mentioned a micro switch. these often have a flat spring to allow a greater movement to be detected. these have both normally open and normally closed contacts, you just pick which you want to use.
these should NEVER, repeat NEVER be used as a plunger where the door pushed the plunger in directly. they have a very small travel and if you slam the door, they wail get damaged, if there is a paper in the door, you would think it was closed, but the switch would not make. rather the switch is to be installed so a glancing movement changes state.
There are also plunger switches for car doors and refrigerator doors and a heavy duty one for closet doors.
these are almost all set to complete the circuit when the door is open.
google door switch

The classic example is a fridge door switch, or a car door switch.

dave-in-nj:
[...] NEVER be used as a plunger where the door pushed the plunger in directly. they have a very small travel and if you slam the door, they wail get damaged, if there is a paper in the door, you would think it was closed, but the switch would not make. rather the switch is to be installed so a glancing movement changes state.
There are also plunger switches [...]

Ahh - the magic term, 'plunger switch'! Thank you for that. A google search on that brings up a number of interesting buttons, which would surely fit my intended purpose. I knew the Danish term for it, but I couldn't translate it and thus had to resort to this topic, and now I'm hopeful a number of other non-English speakers will benefit. Thanks again.