Re: Sol'n to Speed Feedback?

[Tim Vanderhoek <vanderh@ecf.utoronto.ca>]

On Wed, Dec 29, 1999 at 01:02:11AM -0500, Joyce Poon wrote:
> 
> It took a long time, but I managed to find the homepage of the Engineering
> Design course at Rice University (they build robots in 2nd year too).

Gr.  Their site's down right now...


> It is not connected directly to the motors.  I think one attaches an
> interrupter blade (like a fan blade) on the shaft.  And every time the
> blade passes through the magnetic switch (Hall switch/Hall sensor <I

In another email in the "Dropping marker signals" thread, you write:

> I think we can use Hall sensors to measure speed. We just have to mount a
> magnetic switch near the wheel and a companion magnet on the wheel.  So
> every time the magent comes close to the switch, the signal will become
> high/low (ie it'll change).

Hmm...  This sounds fairly easy to do.  Do you have any idea about
whether or not stray emf could cause a problem?  These sensors would
be sitting pretty close to the motors.  That's a lot of potential
emf...

Reading through the Seattle Robotics links you suggested, both of the
two hobby robots discussed, the Genesys and SR04, use optic couplers to
measure the speed.  I think they're also using a supplementary counter
circuit (similar to ones we wired in ece253 labs), though neither
explicitly say so.  They appear to also suggest that suitable optic
couplers are fairly easy to purchase.

I think we can assume that we'll use one of these two solutions.  I'm
convinced that the ability to determine our speed is essential.


-- 
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