Binu Pillai <binu_s_pillai <at> rediffmail.com> writes:

>   yes momentum would be massive...But braking system can be connected to this 
> system if i can give relay
> output.Right now we are controllig the whole system over Wireless...so just
have > to add one more
> interlock to the system...
>  1)distance of 10m would be critical and it has to stop at that distance. 
>  2)distance of 15m can give an alarm.
>  3)breaking distance is 3.5mts

I think that it is worth trying an industrial microwave doorway opener. These
have a distance setpoint and some have vanes that help to direct the beam where
it is needed. You can also add a dielectric lens to make the beam do what you 
need.

Here is an example of device:

  http://www.bircheramerica.com/industrial-door/microwave-sensors.htm

(I have not used this, but similar ones, and there are others)

While this is 'just' a Doppler motion detector it can be adjusted to react at a
desired distance for an object of given reflectance.

Peter P.

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