I need help with the reed switches!!!!!!!

[archiver]

Posted by Chris at 2/11/2001 7:05 PM EST


Student on team #69, HYPER Team 69 Quincy Public Schools Gillette , from North Quincy High and The Gillette Company.



I need help with everything on reed switches! If you can help me please write to me at cmc112784@hotmail.com

I need Help!!!!

[archiver]

Posted by Matt Leese at 2/11/2001 11:08 PM EST


Other on team #73, Tigerbolt, from Edison Technical HS and Alstom & Fiber Technologies & RIT.


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



First of all, look at the specifications for the Reed
switch provided in the manual. The Reed switch is very
simple, it's triggered by a magnet. There are only two
leads and I don't believe you can hook it up backwards.
It is just triggered by a magnet. Simple stuff.

Matt

[archiver]

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