>>>I have used this approach for encoder used in a satellite antenna to read
>>>azimut angle. Got problems with some false pulses which occured when the
>>>encoder is just giving pulses when stopped (wind movement). When this pulses
>>>are in the output connected to the interrupt you will get a false count.
>
>
>I don't understand the problem, yet.
>If the signal causes an interrupt couldn't you just reference the OTHER
>signal to see if there's been any movement (just as Paul described)?

The problem is that encoder is just slightly moved, so it does not produce a
true quadrature pulse output as the rotation angle is less than a true
encoder step. If that pulse triggers the interrupt and you reference to the
other signal you will ever detect the same level. In fact, the level in this
line doesn't change.

> If the wind was causing pulses, then why couldn't you
>decrement/increment the 'degree-of-turns' register accordingly to keep
>track of subtle movement?

In fact the best thing is to IGNORE those pulses while the antenna is
stopped. You get the pulses but they don't indicate true encoder movements.
If you count them you'll get an error and if you look at the other line to
detect direction (up/down) you will get the same direction all the time. In
a few days your encoder counts will not correspond with the encoder position.

Don't know how to explain it better, but this problem is something hard to
see in the theory and easy to get in a real system, with a big antenna dish.

>
>-Pete
>peter.cesarz@appl.ge.com
>


Luis Fernandez Cormenzana
RadioBit Sistemas, S.L.
        Vehicle fleet control systems
        Patrol presence controllers

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