Thread: I need help with the reed switches!!!!!!!
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Unread 24-06-2002, 00:40
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#0047 (ChiefDelphi)
  
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Re: I need help with the reed switches!!!!!!!
Posted by Al Skierkiewicz at 2/13/2001 1:49 PM EST


Engineer on team #111, Wildstang, from Wheeling High & Rolling Meadows High and Motorola.


In Reply to: I need help with the reed switches!!!!!!!
Posted by Chris on 2/11/2001 7:05 PM EST:



Chris,
I hope you have had help by now, but if not...
Reed switches are useful for a variety of applications but you have to know the beast to appreciate it. Essentially, the "leaves" inside move when in the presence of a magnetic field. This can originate in a permanent magnet, (You frequently see this application in alarm system at doors and windows) or through the use of an electric coil magnet. They are fairly reliable when used at design currents and voltages and they are hermetically sealed from the atmosphere. They can be sensitive to stress on the leads, i.e. movement of the lead during closed condition can cause temporary open circuits. Therefore always secure the body and leads. In the presence of magnetic fields the switch will actuate but will "bounce" or make a series of contact open/close cycles before stable contact is achieved. Therefore use suitable "debounce" in software to insure accurate detection of contact closure.
If you wish to experiment, an ohmeter or continuity checker and a magnet will give you a good idea of the sensitivity (how close the magnet needs to be for operation) and you can actually see the "leaves" inside move when a magnet is brought close to the shell. Let me know if you have any specific questions.
Al



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