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Subject: 
Sensor Resistance Readings and Circuit Descriptions
Newsgroups: 
lugnet.robotics
Date: 
Wed, 2 Feb 2005 22:26:15 GMT
Viewed: 
1268 times
  
I’ve added a graph of RCX/Cybermaster sensor resistance vs raw reading to my brickshelf gallery:

There are 3 lines on the graph, with the resistance values on a log axis. The blue plusses are the actual readings. The pink triangles are a first approximation to a cosine curve and the green crosses are a closer approximation with more trigonometric functions in the formula.

This shows the useable range of resistance values being about 100k to 1k, with 10k corresponding to a reading of 512, as you would expect with the 10k internal pull-up to +5V. This helped me choose the resistance values for my passive switch multiplexer as values significantly over 10k, so that the parallel combinations of values would be near to 10k, taking advantage of the maximum slope on the graph and therefore the furthest spacing of readings, to make distinguishing each combination of switches easier. I might post the multiplexer circuit soon.

Also, here is a link to the descriptions of some of the circuits I’ve drawn from my RCX investigation: http://www.brickshelf.com/gallery/mbellis/Technic/Mindstorms/RCX-Internals/rcx_circuit_descriptions.txt

PLMKWYT

Mark



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