A Hall effect sensor acts as a switch. When a magnet crosses the face of
> the Hall the sensor goes from a high impedance to ground. I interface a
PIC
to the Hall via an input pin. Simply, if the input pin goes from a high
to
a low and then high again then a revolution has started. The problem is
> that the hall doesn't know if the rotation is in the forward or the
reverse
direction. Additional sensors or logic is needed for that case.
>
>
>
> > Hi all. I'm using an 8051 to build a very simple robotic machine.
> > Basically a number of feet will be entered by the user before the unit
> > will turn. To calculate this distance I would like to place a sensor
> > on a wheel of the machine and count the rotations of the wheel to
> > calculate the distance.
> >
> > I have a magnetic odometer for my bike that I'm trying to hack, but
> > can any of you offer me any help? I've heard that hall effect ICs work
> > well but I don't know how I would interface them to the 8051.
> >
> > Thanks,
> > Blake
>
>
An Additonal problem you may encounter is wheel spin, in which case the distance computed merely by counting revs and knowing the circumference of the wheel does not equate with the distance travelled by the machine.