This circuit automatically controls room lights and locks based on the number of people in the room. It uses 555 timers, a 74LS192 decade counter, 74LS47 7-segment display driver, and HEF4002B 4-input NOR gate. The counter tracks the number of people and displays it. When someone enters, it increases the count and turns on the lights. When empty, it turns off the lights. The NOR gate controls the relay for locking/unlocking the door based on the people count. It can be useful for monitoring room capacity and conserving energy by automatically turning lights off. Future improvements could include remote monitoring and voice alerts.

1. Automatic Room-lock and Lights circuit
By Amrish

2. Functions of the controller
This controller performs the task of controlling the room lights as well as
counting the number of persons in the room accurately
The total number of persons in the room is displayed on the seven segment
display
When a person enters into the room , the counter is increased by 1 and the
light glows
In the absence of person in the room , the light automatically goes off

3. LIST OF COMPONENTS:
S.no Name of the Components Range
1 IC 1,2,6 555
2 IC 3 74LS192
3 IC 4 74LS47
4 IC 5-HEF- 4002B
5 TRANSISTOR BC547
6 DISPLAY(7 SEGMENT) LTS542
(COMMON ANODE)
7 DIODE IN4007
8 RESISTOR 1,5,12 47 KΩ
9 RESISTOR 2,3,6,7,13 10 KΩ
10 RESISTOR 4,8,9,10,14,15,16 1 KΩ
11 RESISTOR 11 470 Ω

4. 12 CAPACITOR 1,3 100µF,16V
13 CAPACITOR 2,4,6 0.01µF
14 CAPACITOR 5 220µF,16V
15 CAPACITOR 7 470µF,16V
16 CONNECTOR 1,2,3,4,5 _
17 FOOT SWITCH _
18 PUSH BUTTON SWITCH _
19 RELAY 5V,1 C/O
20 adaptor 5V DC
21 DOOR-LOCK ASSEMPLY _

5. IC 555:

6. Explanation:
• Comparator: The Comparator are the basic electronic component which compares the two input voltages i.e.
between the inverting (-) and the non-inverting (+) input and if the non-inverting input is more than the
inverting input then the output of the comparator is high. Also the input resistance of an ideal comparator is
infinite.
• Voltage Divider: As we know that the input resistance of the comparators is infinite hence the input voltage is
divided equally between the three resistors. The value being Vin/3 across each resistor.
• Flip/Flop: Flip/Flop is a memory element of Digital-electronics. The output (Q) of the flip/flop is ‘high’ if the
input at ‘S’ terminal is ‘high’ and ‘R’ is at ‘Low’ and the output (Q) is ‘low’ when the input at ‘S’ is ‘low’ and
at ‘R’ is high.

7. 74LS192:

8. IC74LS47

9. 7-segment display:

10. Types of
seven segment
 Common anode
 Common cathode

11. RELAY CONTROLLER:

12. HFE4002

13. Block Diagram:
UP - Counter
timer
(555)
Down - Counter
timer
(555)
decade
Counter
192)LS(74
Seven
Segment
display
driver
LS(74 47)
Seven
Segment
display
4 Input
NOR gate
Logic
driver
(HEF 4002)
Output
Control
Circuit
Load
Power
Supply
240V AC
+5V
Automatic Room Lock And light Circuits (Blockdiagram)

14. Explanation:
BCD Counter
A BCD counter is a special type of a digital counter which can count to ten on the application of a clock signal. We saw
previously that toggle T-type flip flops can be used as individual divide-by-two counters. If we connect together several toggle
flip-flops in a series chain we can produce a digital counter which stores or display the number of times a particular count
sequence has occurred.
Decade counter
A decade counter is one that counts in decimal digits, rather than binary. It counts from 0 to 9 and then resets to zero.
The counter output can be set to zero by pulsing the reset line low.
Seven segment display :
An LED or Light Emitting Diode, is a solid state optical PN-junction diode which emits light energy in the form of
“photons” when it is forward biased by a voltage allowing current to flow across its junction, and in Electronics we call this
process electroluminescence.
Output control relay circuit
Thus far we have seen a selection of Input devices that can be used to detect or “sense” a variety of physical variables and
signals and are therefore called Sensors. But there are also a variety of electrical and electronic devices which are classed
as Output devices used to control or operate some external physical process. These output devices are commonly
called Actuators.

15. CIRCUIT DIAGRAM:

16. Explanation:
• The circuit, shown in Fig. 1, is built around three NE555 timer ICs (IC1, IC2 and IC6), an up/down
BCD decade counter 74LS192 (IC3), a 7-segment display driver 74LS47 (IC4), 4-input NOR gate
HEF4002B (IC5) and a common-anode 7-segment display LTS542 (DIS1). S1 and S2 are foot
switches. S1 is installed under door-mat of the door used to enter the room, and S2 is installed
under a door-mat just inside the room.
The outputs of IC3 change state synchronously with the low-to-high transitions on the clock inputs.
Separate count up (CPU) and count down (CPD) pins of IC3 are used here. Its parallel pin 11 is
made high and parallel data input pins 15, 1, 10 and 9, along with master reset pin 14, are made
low in this circuit.
The outputs (Q0 through Q3) of IC3 are given to IC4 to drive display DIS1. Resistor R11 is used to
limit the current flowing through DIS1.
Outputs of IC3 are also given to IC5. output O1 of IC5 is fed to relay-driver transistor T3 through
resistor R9 to energise relay RL1. Light switches off when RL1 is energised. The second output O2
is fed to relay-driver transistor T4 to energise relay RL2 for locking the door. RL1 and RL2
energise simultaneously as inputs of 4-input NOR gate (IC5) are connected to both the drivers.

17. Output O2 of IC5 is also given to the base of transistor T7 whose collector is connected to the base of transistor T6.
When O2 of IC5 goes high, it locks the door and makes the Vcc pin 8 of IC1 low to stop further counting.
To open the lock, press switches S3 and S4 (acting as security keys) simultaneously. The mononstable circuit built
around NE555 (IC6) triggers and its output goes high for around 11 seconds and makes the base of transistor T4
low, via transistor T5. This action de-enegises relay RL2 to open the lock for a pre-defined time period based on the
values of R12 and C5. At least one person should enter the room within this time period, otherwise it will get locked
again. During this period, Vcc pin 8 remains high to enable IC1.
When each person enters the room and presses foot switch S1, counter IC3 advances by one count and display
shows the number of persons in the room. On first person’s entry, the outputs O1 and O2 of IC5 go low, transistors
T3 and T4 stop conducting and relays RL1 and RL2 de-energise to switch on the light and open the door lock.
Similarly, when they start leaving the room by enabling foot switch S2, counter IC3 reduces by one count and the
display shows the number of persons present in the room. the outputs O1 and O2 of IC5 remain low, so light
remains on and door remains open till the room is vacant.

18. Advantages and future development
It can be used in various rooms like seminar halls , where the capacity of the
room is limited and should not be exceeded
It can be used in our homes because we often forget to switch off our room
lights
It helps in energy conservation
In future , we can send this data to remote areas using mobile or internet
Voice alarm system can be used to indicate that room is full & person can’t
enter inside

19. Thank You