Changes between Version 15 and Version 16 of ControlSystems/SoftwareTeam/Training/GettingStarted/Encoders

Timestamp:

Oct 31, 2019, 1:24:05 PM (6 years ago)

Author:

David Albert

Comment:

--

ControlSystems/SoftwareTeam/Training/GettingStarted/Encoders

@@ -65 +65 @@
 Note: you'll need to manually turn the left wheel forward and backward to see the Encoder values change. Try turning the wheel 360 degrees to see what value is equivalent to a full revolution of the wheel.  
 
+=== Quadrature Encodures
 
+[[Image(encAB.gif,left,250px,margin=10)]][[Image(quadEncoder2.gif,right,250px,margin=10)]]Notice that the raw count reports 2x360=720 counts per rotation.  This is because the encoders used are quadature encoders which have two channels: A, B and the sum of both A and B channels are reported.  A quadrature encoder works like the optical encoder shown above, but with two rows of slits in the disk, each slightly offset from the other (overlapping) and each with its own light source/detector.  This allows you to determine not just distance and speed but also direction.  The light detectors are labeled A and B; because the slots overlap, the sequence of detected light as the wheel rotates forward is:  A, AB, B, off, A, AB, etc.  When the wheel rotates backwards, the sequence is B, AB, A, off, B, AB, A, off.  
 
-[[Image(encAB.gif,right,250px,margin=10)]]Notice that the raw count reports the sum of both A and B channels of the quadrature encoder.  A quadrature encoder works like the optical encoder shown above, but with two rows of slits in the disk, each slightly offset from the other (overlapping) and each with its own light source/detector.  This allows you to determine not just distance and speed but also direction.  The light detectors are labeled A and B; because the slots overlap, the sequence of detected light as the wheel rotates forward is:  A, AB, B, off, A, AB, etc.  When the wheel rotates backwards, the sequence is B, AB, A, off, B, AB, A, off.  
-
-You can read more about quadrature encoders [https://robu.in/quadrature-encoder/ here] [[Image(quadEncoder2.gif,right,250px,margin=10)]]
+You can read more about quadrature encoders [https://robu.in/quadrature-encoder/ here] 
 There are many types of encoders; the ones shown here use light, but there are magnetic, capacitive, and other detection mechanisms.  Encoders can have a single channel (A) to determine speed and distance traveled, two channels (A,B) to determine speed, distance, and direction, and many encoders have a third channel (A, B, Z) where the Z (index) channel only provides a single pulse per full rotation of the wheel.  This can be useful if you need to move the motor to a precise position.