Using Magnets

Our team wants to use a limit sensor to calculate when we want a motor to start and stop. The one problem with this is the limit sensor would be destroyed by a fast moving piece of medal. We want to use a magnetic proximity switch(or something like that that triggers a button via a magnet) but we do not know if it is legal. Has anyone else had this idea and found out whether it is legal for the 2008 competition?
Julian

The rules say nothing about that type of sensor. If you are unsure, I would talk to Q&A. At this point, probably legal if it is under the cost limit. (Note: the Gear Tooth Sensors are magnetic sensors.)

Team 1501 is thinking of using a Mag Lev :smiley:

We used a magnetic contact like an alarm system would have two years ago. It worked ok because it would move so fast it would miss it sometimes. It just depends if that affects your application or not.

As far as I know magnets are fine on the robot. The gear tooth sensor supplied with the kit of parts is magnetic and the motors generate magnetic fields while being used. Last year we considered using a magnetic latching system and found nothing against it in the rules.

Melexis 90217 Hall-Effect Sensor

Short circuit protection
Rotary position gear tooth sensing ability (using a magnet is better)
On-chip 10 bit A/D converter
Self-adjusting magnetic range
High speed operation
No chopper delay
Zero speed detection
No rotary orientation concerns

It is normally pulled high and goes low when it detects a magnets south pole. It should be real easy to watch with the IFI controller.

Thanks Guys. Capt. Quirk showed a sensor that we could possibly use but i don’t know if it will work for us. Does anyone else have any ideas?
Julian