Magnet lift / on / cupboard lighting, how does it work ?

[petemoore]

  First...it's a little LED/Battery/circuitboard.
  And in the circuit board is a switch which is activated magnetically.
  The light sticks to the cupboard board, the little magnet plate sticks to the door.
  When the door opens the magent comes away from the sensor, and the light lights.
  Kinda nifty. And nice strong little magnets.
  First thing comes to mind of course is how-whether to try to apply it to DIYSB's.
  I can think of numerous ways to use something like this, and the possible hurdles...
1.  Like the switch/sensor circuit has the bulb as a circuit component?
2. There is no 'floating' switch, such as an SPST, the switched 'wire' must have a voltage on it for the switch to work.
3. ...anything else...
  They are readily and affordably available...wondering if I could find the circuit it uses to magnetically sensor switch and diddle with that.
  Nope...havne't done a bunch of searching, but I might, just testing the waters to see if there's been any current or old interest in such devices around.

[frequencycentral]

Mercury switch. 

[Ice-9]

Probabally a reed switch. the magnet holds the switch in an on/off position. when the magnet is moved it releases the switch to the other position. I would think the same as you find in alarm door contacts. They could make an interesting idea for a pedal

[petemoore]

  If I could hook a resistor off ground through the switch [frinstance, if the switch is 'floating'], it'd be usable, might be 'poppy'..noise in signal path.
  It looks like it could be part of a turns counter on my yet to be fully DIY'd coil winder [sewing machine].
 

[sean k]

Maybe a hall effect device is what you want for your winder which is exactly what they use on ignitions. Except you don't need a magnet, there one already in the thing and it has a gap where a rotating finger or tab passes through the gap. They are easily linked to tachometers so it might be quite simple to hook up something that just counts.