CONTACT LESS TACHOMETER USING MICROCONTROLLER
ABSTRACT
A tachometer is nothing
but a simple electronic digital transducer. Normally, it is used for measuring
the speed of a rotating shaft. The number of revolutions per minute (rpm) is
valuable information for understanding any rotational system. For example,
there is an optimum speed for drilling a particular size hole in a particular
metal piece; there is an ideal sanding disk speed that depends on the material
being finished. You may also want to measure the speed of fans you use.
It is a microcontroller
based tachometer that is used to measuring the speed of a rotating shaft. Just
point the light sensitive probe tip atop the spinning blade, disk or chunk and
read the rpm. The only requirement is that we have to place a contrasting color
mask. Position it such that the intensity of light reflected from the objects
surface changes as it rotates. Each time the tape spins past the probe, the
momentary increase in reflected light is detected by the photo transistor. The
pulses picked up by the phototransistor are amplified by transistor and sensed
by the internal comparator of AT89C2051 and, through software, each pulse representing
one rotation of the object is detected. By counting the number of such pulses,
on an average per minute basis, the RPM is evaluated. It is displayed by a
software routine to light up the LED segments of the 4-digit, 7-segment
display.
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