Visitor
counting is simply a measurement of the visitor traffic entering and exiting offices,
malls, sports venues, etc. Counting the visitors helps to maximise the efficiency
and effectiveness of employees, floor area and sales potential of an
organisation.
Visitor
counting is not limited to the entry/exit point of a company but has a wide
range of applications that provide information to management on the volume and
flow of people throughout a location. A primary method for counting the visitors
involves hiring human auditors to stand and manually tally the number of
visitors who pass by a certain location. But human-based data collection comes
at great expense. Here is a low-cost microcontroller based visitor counter that
can be used to know the number of persons at a place. All the components
required are readily available in the market and the circuit is easy to build.
Two
IR transmitter-receiver pairs are used at the passage: one pair comprising IR
transmitter IR TX1 and receiver phototransistor T1 is installed at the entry
point of the passage, while the other pair comprising IR transmitter IR TX2 and
phototransistor T2 is installed at the exit of the passage. The IR signals from
the IR LEDs should continuously fall on the respective phototransistors, so
proper orientation of the transmitters and phototransistors is necessary.
Circuit
description
Two
similar sections detect interruption of the IR beam and generate clock pulse
for the microcontroller. The microcontroller controls counting and displays the
number of persons present inside the hall. above figure shows the circuit of the microcontroller-based
visitor counter, wherein the transmitter and the receiver form the IR detection
circuit. Control logic is built around transistors, operational amplifier LM324
(IC1) and flip-flop (IC2). When nobody is passing through the entry/exit point,
the IR beam continuously falls on phototransistorT1. Phototransistor T1
conducts and the high voltage at its emitter drives transistor T3 into
saturation, which makes pin 3 of comparator N1 low and finally output pin 1 of
comparator N1 is high. Now if someone enters the place, first the IR beam from
IR TX1 is interrupted and then the IR beam from IR TX2. When the beam from IR
TX1 is interrupted, phototransistor T1 and transistor T3 cut-off and pin 3 of
comparator N1 goes high. The low output (pin 1) of comparator N1 provides
negative trigger pulse to pin 1 of J-K flip-flop IC2(A). At this moment, high
input at ‘J’ and ‘K’ pins of flip-flop IC2(A) toggles its output to low. On the
other hand, the low input at ‘J’ and ‘K’ pins of IC2(B) due to clock pin 1 of IC2(A)
and ‘J’ input (pin 9) and ‘K’ input (pin 12) of IC2(B) are connected to pin 1
of comparator N1. The negative-going pulse is applied to clock pin 6 of IC2(B)
when the person interrupts the IR beam from IR TX2. There is no change in the
output of IC2(B) flip-flop. This triggers the external interrupt INT0 (pin 12)
of microcontroller AT89C52. The AT89C52 is an 8-bit microcontroller with 8 kB
of flash-based program memory, 256 bytes of RAM, 32 input/output lines, three
16-bit timers/counters, on-chip oscillator and clock circuitry. A 12MHz crystal
is used for providing clock. Ports 0, 1 and 2 are configured for 7-segment
displays. Port-0 pin is externally pulled up with 10-kilo-ohm resistor network
RNW1 because port-0 is an 8-bit, open-drain, bidirectional l, input/output
(I/O) port. Port-1 andport-2 are 8-bit bidirectional I/O ports with internal
pull-ups (no need of external pull-ups). Port pins 3.0 and 3.1 are configured to
provide the set pulse to J-K flip-flops IC2(A) and IC2(B), respectively.
External interrupts INT0 and INT1 receive the interrupt pulse when the person
interrupts the IR beams. Resistor R9 and capacitor C5 provide power-on-reset pulse
to the microcontroller. Switch S1 is used for manual reset. When the
microcontroller is re- s e t , t h e flip-flops are b r o u g h t i n ‘ s e t ’
s t a t e through the microcontroller at software run time by making their
‘set’ pin high for a moment. The value of the counter increments by ‘1’ when
the interrupt service routine for INT0 is executed .The output of the
corresponding J-K flip-flop is set to ‘high’ again by making its ‘set’ input
pin low through the microcontroller. The micro-controller is configured as a negative-edge
triggered interrupt sensor. Similarly, if somebody exits the place, first the
IR beam from IR TX2 is interrupted and then the IR beam from IR TX1. When the
beam from IR TX2 is interrupted, output pin 7 of comparator N2 goes low. This provides
clock pulse to pin 6 of J-K flip-flop IC2(B).
At this moment,
the high input
at ‘J’ and ‘K’ pins of flip-flop IC2(B)
toggles its output to low. On the other hand, the low input at ‘J’ and ‘K’ pins
of IC2(A) due to clock pin 6 of IC2(B) and ‘J’ input (pin 4) and ‘K’ input (pin16)
of IC2(A) are connected to pin 7 of comparator N2.
The negative-going pulse is
ap- plied to clock pin 1 of IC2(A) when
the person interrupts the IR beam from IR TX1. There is no change in the output
of IC2(A) flip-flop. This triggers
the external interrupt INT1 (pin 13) of
microcontroller AT89C52. The value
of the counter decrements by ‘1’ when interrupt service routine for INT1 is ex-
ecuted. The output of the correspond ing J-K flip-flop is set to ‘high’ again by
making its ‘set’ input pin low through the microcontroller.
The circuit
is powered by regulated 5V. Above figure shows the circuit of the
power supply. The AC mains is stepped down
by transformer X1 to deliver secondary output of
7.5V,
250mA,
which is rectified by bridge rectifier BR1,
filtered by capacitor C6 and regulated by IC 7805 (IC4). Ca- pacitor C7 bypasses any ripple
in the regulated output.
code:
