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Subject: 
RE: Motor Sensor (fwd)
Newsgroups: 
lugnet.robotics
Date: 
Wed, 9 Jun 1999 12:24:17 GMT
Original-From: 
Jim Choate <RAVAGE@EINSTEIN.SSZ.COMspamless>
Viewed: 
1218 times
  
----- Forwarded message from Tilman Sporkert -----

From: "Tilman Sporkert" <tilman@activesw.com>
Subject: RE: Motor Sensor (fwd)
Date: Tue, 8 Jun 1999 18:46:09 -0700

These are DC motors, you better get a reverse current (and as a
consequence
reverse voltage) or else that motor has some sort of diode in it.

Yes, you get a reverse current, but the RCX won't be able to measure that.
Anything below 0V will read the same as 0V (RAW = 0), and anything above +5V
will read as 1023 in RAW mode.

----- End of forwarded message from Tilman Sporkert -----

I have two words....

signal conditioning

What you're looking for is to be able to read gross shaft speed (that's
rpm's and the revolutions part automaticaly implies angular accelleration -
just trying to shutdown the traffic that's going to come over this point)
and direction.

Considering the level of resolution on a DC motor that's pretty poor. So,
what do we do?

Let's assume that the motor puts out a voltage that's +/- 3V depending on
input shaft direction. Re-scale the signal so that all + voltages (say cw
rotation) is 1.5V or greater and that all - voltages are less than 1.5v.
We're also looking to increase the effective (not dynamice) range of the
signal to a 5v swing.

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