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[DPRG] sharp IR distance sensors

Subject: [DPRG] sharp IR distance sensors
From: David Anderson davida at smu.edu
Date: Sun Jul 29 10:30:32 CDT 2012

Howdy,

I got a couple of questions at the DPRG meeting yesterday about using 
the SHARP IR distance detectors and thought of a couple of points I 
might add to the presentation.

First, the A/D converter that nBot currently uses has 1k pullups on all 
the inputs and the SHARP detectors don't have enough oomph to drive the 
inputs directly.  To solve this, a quad opamp chip was added with the 4 
opamps configured as simple voltage followers to drive the A/D inputs 
for the 4 detectors on nBot.  YMMV.

Second, converting the SHARP output voltage readings to linear inches 
requires a simple multiple and divide with some calibration numbers that 
are very easy to determine.  Larry Barello (formerly of the SRS club) 
has an excellent web page that details the measurements and maths:

<http://barello.net/Papers/GP2D02/index.htm>

This deals primarily with the now discontinued GP2D02 sensor, but the 
math applies to all the SHARP detectors.


hope this is useful
dpa


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