Microcontroller-bAsed bidirectionAl Visitor counter
UMAR SUNIL K
AkshAy MAthur, kuldeep singh nAglA
isitor 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 Semiconductors: IC1 - LM324 quad op-amp IC2 - 74LS76 J-K flip-flop IC3 - AT89C52 microcontroller IC4 - 7805 5V regulator T1, T2 - L14F1 npn phototransistor T3, T4 - 2N3904 npn transistor IR TX1, IR TX2 - IR transmitting LED BR1 - 1A bridge rectifier DIS1-DIS3 - LTS543 CC 7-segment display Resistors (all ¼-watt, ±5% carbon): R1, R2 - 68-ohm R3, R4 - 6.8-kilo-ohm R5, R6 - 100-ohm R7, R8, R10, R11 - 10-kilo-ohm R9 - 4.7-kilo-ohm R12-R32 - 220-ohm VR1, VR2 - 20-kilo-ohm preset RNW1 - 10-kilo-ohm resistor network Capacitors: C1, C2 C3, C4 C5 C6 C7 Miscellaneous: XTAL X1 S1 S2 - 0.2µF ceramic disk - 33pF ceramic disk - 10µF, 16V electrolytic - 470µF, 25V electrolytic - 0.1µF ceramic disk - 12MHz crystal - 230V primary to 7.5V, 250mA secondary transformer - Push-to-on switch - On/off switch
Fig. 1: Transmitter-receiver set-up at the entrance-cum-exit of the passage
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 microcontrollerbased 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.
Fig. 1 shows the transmitter-receiver set-up at the entrance-cum-exit of the
passage along with block diagram. 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. Fig. 2 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 phototransistor T1. 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, the high input at ‘J’ and ‘K’ w w w. e f y m ag . co m
7 8 • J a n ua ry 2 0 0 7 • e l e c t ro n i c s f o r yo u
w w w. e f y m ag . co m
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Fig. 2: Circuit of the microcontroller-based visitor counter
Fig. 3: Power supply circuit
pins of flip-flop IC2(A) toggles its...
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