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Door intrusion and water level sensor

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fubuaks

New Member
I m doing this project in which the unit (microcontroller,pcb) is placed inside a cabinet.
I need a sensor for detecting any attempt of theft, as in, if anybody opens the door of the cabinet a command is send to the microcontroller.
Another sensor is required for detecting the water level, if it goes low below a certain level, the uc gets interrupted.

What kind of sensors i shud go for and where can i find theory about them?
If anybody could provide help on these two things.....
 

KMoffett

Well-Known Member
For the door, look at magnet/reed switches like those used in home alarm systems. For the water level detector a float switch would be the simplest.

Look at how switches are interfaced to micro-controllers.

Are there any other limiting specifications?

ken
 

fubuaks

New Member
Thanks KMoffett and gerty for ur replies......

I searched about the reed switches and yes they are appropriate for my application. But how do i connect one to the door and its interfacing to the microcontroller...?
 

Boncuk

New Member
like this.

If you require the signal inverted connect an NPN transistor between switch and MCU port pin.
 

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KMoffett

Well-Known Member
like this.

If you require the signal inverted connect an NPN transistor between switch and MCU port pin.
Or, reverse the positions of the resistor and reed switch.

Also note, when purchasing reed switches that some are normally-open (N.O.) and a magnet closes the contacts. Others are normally-closed (N.C.) and a magnet opens the contacts.


Ken
 

Boncuk

New Member
Or, reverse the positions of the resistor and reed switch.

Ken

That depends on the kind of MCU. Some only understand an active pullup, and want to see ground potential (or close to ground) when low.

Boncuk
 

fubuaks

New Member
I am going to use atmel's 89s52.......i searched on reed and float switch, but their are many varieties of them available, which model should i go for....?my app is a simple one, so not complex one's i guess.....?
 

KMoffett

Well-Known Member
For the float switch, you have to be specific about the water container you're monitoring. Each type of float switch works best in a specific environment. Though the "app is a simple one" the "devil is in the details". Can you give us details.

For the door switch, something like this: Directed 8600 Magnetic Micro Switch - RadioShack.com

Ken
 

blufke03

New Member
sensors

Hello,
If you are looking for a sensor, you should visit Madison Company's website. They have a large variety of sensors, along with information on sensors so that you know exactly which sensor is right for the project that you're working on.
I hope that this helps you!
 
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