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Element945
01-17-2003, 12:25 PM
Can we use it and what can we use it for?

PyroPhin
01-17-2003, 07:47 PM
What?!?!

please clairify...

~Pyro

seanwitte
01-17-2003, 08:38 PM
Those switches are used to detect nearby metal. They have a range of less than 10mm, so you're better off using a mechanical limit switch. They're expensive as well.

If you're looking for a non-contact switch for something, check out Hall Effect or reed switches.

Element945
01-17-2003, 11:05 PM
Well first of all I'm glad that someone knew what we were talking about! One of our Mentors who we will not see in person until next week had asked us if we were allowed to use "inductive proximity switches", which he said he might have on hand. I forgot to find out where they are from but I thought I might try to find out in advance if such a switch would be allowed, I think it is, by the flow chart. By your reply I am not sure now what he has in mind for them, but it would still help to find out this info. Thanks for the help by the way, and watch out for Team 945 this year!!

Jnadke
01-17-2003, 11:37 PM
There are 2 types of proximity sensors [switches]:

Inductive: These build a magnetic field around the sensor. Inductive proximity switches will only trigger when in the presense of a magnetic object (iron, cobalt, or nickel). Hint: This would be handy for detecting when you are over the steel mesh.
Inductive Proximity Sensors (http://dkc3.digikey.com/PDF/T031/1046.pdf)

Capacitive: These use an electric field to detect metallic and non-metallic objects. Every element has it's own dielectric constant (k). The sensor uses a reference material and detects a difference in capacitance. These can be used to detect other robots, containers, etc.
Capacitive Proximity Sensors (http://dkc3.digikey.com/PDF/T031/1048-1050.pdf)


Remember, you can only use the sensors from Digikey (http://www.digikey.com) or Future-Active (http://www.future-active.com). If they carry that manufacturer and model of sensor, then use it if you have them lying around.


If they are non-powered, they don't count toward the $200 electronics limit.

If they are powered, you have to count them.

Element945
01-18-2003, 10:51 AM
Thanks , that helps a lot!

Al Skierkiewicz
01-18-2003, 06:35 PM
Element,
Jnadke is right on in his description, check the specs though and you will see that the range is only 5 mm. If you were able to mount them in such a way that you could take advantage of the short range that would be cool to see.

Element945
01-21-2003, 08:10 AM
Thanks guys your a lota help. I was thinking about using it to measure how high our stack is with strips of metal. I cant be more detailed because i dont wanna give your team any ideas :( sorry.

Element945
01-21-2003, 09:23 AM
Originally posted by Jnadke
There are 2 types of proximity sensors [switches]:

Inductive: These build a magnetic field around the sensor. Inductive proximity switches will only trigger when in the presense of a magnetic object (iron, cobalt, or nickel). Hint: This would be handy for detecting when you are over the steel mesh.
Inductive Proximity Sensors (http://dkc3.digikey.com/PDF/T031/1046.pdf)

Capacitive: These use an electric field to detect metallic and non-metallic objects. Every element has it's own dielectric constant (k). The sensor uses a reference material and detects a difference in capacitance. These can be used to detect other robots, containers, etc.
Capacitive Proximity Sensors (http://dkc3.digikey.com/PDF/T031/1048-1050.pdf)


Remember, you can only use the sensors from Digikey (http://www.digikey.com) or Future-Active (http://www.future-active.com). If they carry that manufacturer and model of sensor, then use it if you have them lying around.


If they are non-powered, they don't count toward the $200 electronics limit.

If they are powered, you have to count them.


How would they be "non-powered" ?

Jnadke
01-21-2003, 01:24 PM
Non-powered as in... not requiring extra power directly from the battery. The digital inputs supply 5V @ 10mA of power to all switches. The digital input is the (+) terminal and the ground (-) is common. For example, the optical sensors would be classified as powered switches, because they require an external power source to operate. Limit switches, on the other hand, require no external power source, and would be considered non-powered.

The restricted hardware list says that you can use an "unlimited amount" of switches, as long as they are not powered, meaning they cannot rely on external power to activate the switch. Under this classification, they would not need to fall inside the $200 extra parts limit either. If they are powered, you'd be in the $200 limit.




I'd imagine you're thinking about using the proximity sensors to detect the hight of your stack by detecting various increments. You might want to consider using "reed switches". They're little switches that you wire, and are activated by a magnet. When a magnet comes in proximity to it, the lever becomes attracted to it and closes the circuit. When the magnet is removed, the lever goes back, and the circuit is open.

Just put a reed switch on your lift mechanism, and bolt magnets at various hights on your lift. Or you can do it the other way around. Bolt a magnet to your lift mechanism, and put reed switches on your lift. Either way works, and will be more reliable and less costly than inductive proximity switches.

Digikey has them, but if you can find them at a local electronics retailer/distributor, it'd be easer to get them from them. Since they are classified as switches, you can get them from anywhere, and not just digikey.
http://dkc3.digikey.com/PDF/T031/0833-0834.pdf