[mowbot] Colour sensor

robin nospam at acm.org
Tue, 5 Nov 1996 17:13:42 GMT

I have done some simple and successful experiments to detect the
colours of objects using just some LEDs and a light-dependant resistor.
By measuring the relative brightness of the differently coloured reflected
light from the LEDs one by one, it is easy to get a good idea of the
colour of the object causing the reflections. The cheap LDR I am using
is sensitive to a wide range of wavelengths from infra-red, through red
and green, to blue.

So far, I have only done tests in a controlled environment where I
can exclude interference from other light sources and ensure that only
uniform colours are in the sensor's field of view. For in less
well-defined circumstances, it should be possible to use modulated light
to eliminate daylight interference and add a lens or collimator to
look at only a small area.

Detecting colour sounds like it will be useful for all sorts of things.
Since everything that needs cutting is in the green/yellow part of
the spectrum, and most things that don't need cutting aren't, it should
provide a pretty good boundary detector that requires no training. But it
may also provide a means for placing simple signs in the environment
and prove useful in distinguishing paths that can be followed or
additional boundaries that should not be crossed.


Copyright (C) 1996 R.M.O'Leary <robin nospam at acm.org>  All rights reserved.
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