piclist 1998\11\19\130333a >
Thread: Object Speed Counting in sunlight.
picon face BY : Peter L. Peres email (remove spam text)

On Thu, 12 Nov 1998, Mike Chaloupka wrote:

> I need to detect the speed of an object 2 - 5 feet from the sensor mount.
> Sensor is mounted upward looking at the sky.

The optical way is easy, using a CW light source in the night and the sun
in the day, but one uses more than one sensor (more like a matrix -
minimum size 2 x 2) connected to a micro. This eliminates dirt etc sensing
and can tell which way the object is passing, also has an early failure
indicator built-in (sensors won't fail together unless someone paints
them over very quickly <g>).

I did something similar for a protection device on an exhaust chimney and
I used 4 Al. tubes of different lengths in a pipe-organ style mount with
glass windows and CdS photoresistors at the bottom connected to a LM324.
The LM324 was connected as adaptive AC amplifier (to remove DC bias). The
light was a parlight and was on all the time with a current sense resistor
in one of the return wires. Outputs went to a Z80 based controller that
also did other things.

hope this helps,



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