[nzlug] Embeded problem - Dairy

[Andrew Errington]

>
> The biggest cost i would have thought is automating the gate. Cows are
> BIG really BIG, and strong. If he doesn't already have a reliable
> electro-mechanical gate (ie one you can push a button and it opens/closes
> etc) then there is a bit of cost in an electro-mechanical system to do it
> reliably in that dirty, wet environment populated by big animals.
>

True, but most suggestions made here have assumed that the gate mechanism
is separate, and that the 'cow detector' has a simple output that opens or
closes the gate.  It is also true that each design has its benefits and
potential problems.  An engineer's job is to design a system that works
with an acceptable performance within the given constraints.

A solution to the gate problem might be to have the 'cow detector' flash a
light and sound a horn when the cow walks past, then an assistant could
operate the gate at the right time, leaving the dairyman to concentrate on
the dairying.

Generally for this kind of problem you design a strong gate and fixture
and have a lightweight actuator that won't be damaged if it is jammed or
forced.  For example, a motorised arm that connected by a spring to the
gate.  If the gate is free to move then the motor will move the gate to
the desired position, but if the gate is not free to move then motor will
compress or stretch the spring rather than destroy itself.

Andrew