H. Smit wrote:
>
> hello,
>
> I'm working on a project to operate my driveway gate by using satellitedish
> motors. for the mechanical part it went ok, but for the electronical part i
> have some difficulties. I want to operate my gate by driving over an
> detection loop in my driveway, the kind they use by traffic lights. maybee
> one of you can give me a hint of how these detection loops are working.
>
> Please advise,
> Regards,
> Henk Smit.


They detect the change in inductance of a coil caused by
a nearby metal object.

Usually they're set up in a figure 8 pattern so nearby mag
fields don't affect them. Only having a metal object over one
half of the figure 8, but not the other.
--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html