How does laptop detect that the lid is closed?

[starLED]

I was looking at how does my laptop shutdown automatically when I close the lid, but it's not clear to me how is working.
I don't see any switch that is pressed by the lid, or some sensor like the phones have for turning off the screen when you talk.
How does this work?

 

[Nigel Goodwin]

I've never been interested enough to look, but it's simple enough - either a little mechanical switch somewhere, or a reed switch and a magnet, or even a hall effect switch and a magnet.

 

[starLED]

There are little magnets on the side of the screen, I guess there is something on the motherboard to detect.

 

[rjenkinsgb]

Mine (Panasonic) have a magnetic sensor (presumably hall effect) near the front, next to the trackpad area.

I discovered that because my placing my phone in just the right position puts the laptop in to standby!

 

[Nigel Goodwin]

Mine (Panasonic) have a magnetic sensor (presumably hall effect) near the front, next to the trackpad area.

I discovered that because my placing my phone in just the right position puts the laptop in to standby!

Nice one!

 

[qazwiz]

yeah, use a magnet near your laptop to find a hall effect resistor... reed switches need bigger magnets so likely too bulky
a mechanical device that works like a pop-up greeting card would also work but is too delicate to be reliable (plus you would notice a rod like item sliding into place)