Progress_2_x - Engineering for Change

bendembarrassΗλεκτρονική - Συσκευές

2 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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Soundless Horn

Source section

Astable

Multivibrator


The TSOP 1738(IR sensor) requires an incident
signal with a centre frequency of 38khz.


So the Infra red LED must be illuminated by a
signal that has a frequency of 38khz.


This is accomplished by generating the
required signal using an
atable

multivibrator
.


Source section

Advised data format


The main intricacy involved with the TSOP
1738 is that a continuous signal of 38khz is
treated as noise.


There is a suggested data format of sending IR
pulses to the sensor.


They should be in the form of bursts of cycles.


The bursts should have 10
-
70 cycles

Data format
(contd.,)


There should be a gap of at least 14 cycles
between the bursts.


While all these criteria being satisfied, the
frequency of the pulse train must be kept at
38khz.

Monostable

multivbrator

#2


As the format consists of bursts, to produce a
burst of cycles the
astable

should be on and
for the gap between the bursts it should be
off.


This can be achieved by drawing the
supply(
Vcc
) of the
astable

from the output of
the
monostable

multivibrator
.


Monostable

multivbrator

#2
(contd.,)


As there should be 10
-
70 cycles/burst based
on the frequency of the
astable

output signal
its time period can be calculated and hence
the time required for 20 cycles is determined.


This becomes the on time of the
monostable

multivibrator

#2.


Similarly based on the gap between the bursts
reqiured

the Off time should be adjusted.

Monostable

multivbrator

#1


This
multivibrator

forms the initial block of the
source section.


A driver while blowing a horn excites this
multivibrator
. This is nothing but the trigger to
the
multivibrator
.


It generates a signal that sustains for a
duration of 0.5 sec.


This forms the supply of the
monostable

#2.

Source section using Microcontroller


The circuit using
multivibrators

is only for
testing purpose


For accuracy and to reduce bulkiness, the same
can be implemented using Microcontroller