sensor detecting opened suitcase?

[tdb]

I am working on a project that will transmit an rf signal whenever a suitcase is opened up. The only hangup I'm having right now is on what type of sensor to use to detect when the main compartment of the suitcase is opened. Some options I've come up are:

1) reflective IR -- but it seems likely that the sensor could be blocked by a person's hand, arm, etc. so that the sensor "thinks" the suitcase is closed
2) contact closure on zipper -- but they have those cheap plastic zippers
3) hall-effect sensor -- put a hall-effect in the suitcase and a manget into the door compartment. But I'm not sure if I can fine-tune this to only activate if it's open more than 2-3".

Anyone have ideas on other types of sensors? Thanks!

p.s. Don't worry... these suitcases will not be used as air travel luggage!

 

[tansis]

Sometimes the simplest solution would be a simple micro-switch, mounted towards the rear of a briefcase near the hinge. Photo-relective sensors typically have a sense range of only a few millimeters before a change of state occurs and could only be fooled if you know where in the case it is located.The hall ic would work but it is a bit of an overkill, but might be usefull for detecting a small weak magnet glued to the under/inside portion of a plastic zipper.

Other solutions:
Capacitive proximity (search net for "Theramin" circuit ) could be worth an experiment as would a touch sensor circuit (the archives are full of these) Tilt and in particular vibration switches could also be used.

Sounds like a good project.

 

[Jimbo]

Can't you place the magnet across a 'reed relay' (I hope I got that right in English) in stead of the Hall-IC? I suppose mercury filled examples are out of the question because you could turn the suitcase upside down or sometihng to force the mercury into "contact" position when the magnet is gone, but spring operated reed relays should work.

Personally I would go for a strategically placed microswitch.

 

[Gene]

Sure. Place the magnet/reed pair near the edge that will open first - not the hinge side.