Multiplexer

Multiplexer means many into one. A multiplexer is a circuit used to select and route any one of the several input signals to a single output. A simple example of an non-electronic circuit of a multiplexer is a single pole multi-position switch.

Multi-position switches are widely used in many electronics circuits. However, circuits that operate at high speed require the multiplexer to be automatically selected. A mechanical switch cannot perform this task efficiently. Therefore, multiplexer is used to perform high speed switching are constructed of electronic components.

Multiplexers can handle two type of data i.e., analog and digital. For analog application, multiplexer are built using relays and transistor switches. For digital application, they are built from standard logic gates.

The multiplexer used for digital applications, also called digital multiplexer, is a circuit with many input but only one output. By applying control signals (also known as Select Signals), we can steer any input to the output. Some of the common types of multiplexer are 2-to-1, 4-to-1, 8-to-1, 16-to-1 multiplexer.

Following figure shows the general idea of a multiplexer with n input signal, m control signals and one output signal.

Understanding 4-to-1 Multiplexer

The 4-to-1 multiplexer has 4 input bits, 2 control or select bits, and 1 output bit. The four input bits are D0,D1,D2 and D3. Only one of this is transmitted to the output Y. The output depends on the values of A and B, which are the control inputs. The control input determines which of the input data bit is transmitted to the output.

For instance, as shown in figure, when  A B = 0 0 , the upper AND gate is enabled, while all other AND gates are disabled. Therefore, data bit D0 is transmitted to the output, giving Y = Do.

If the control input is changed to  A B = 1 1 , all gates are disabled except the bottom AND gate. In this case, D3 is transmitted to the output and Y = D3.

• An example of 4-to-1 multiplexer is IC 74153 in which the output is same as the input.
• Another example of 4-to-1 multiplexer is 45352 in which the output is the compliment of the input.
• Example of 16-to-1 line multiplexer is IC 74150.

Applications of Multiplexer

Multiplexer are used in various fields where multiple data need to be transmitted using a single line. Following are some of the applications of multiplexers –

1. Communication System – Communication system is a set of system that enable communication like transmission system, relay and tributary station, and communication network. The efficiency of communication system can be increased considerably using multiplexer. Multiplexer allow the process of transmitting different type of data such as audio, video at the same time using a single transmission line.
2. Telephone Network – In telephone network, multiple audio signals are integrated on a single line for transmission with the help of multiplexers. In this way, multiple audio signals can be isolated and eventually, the desire audio signals reach the intended recipients.
3. Computer Memory – Multiplexers are used to implement huge amount of memory into the computer, at the same time reduces the number of copper lines required to connect the memory to other parts of the computer circuit.
4. Transmission from the Computer System of a Satellite – Multiplexer can be used for the transmission of data signals from the computer system of a satellite or spacecraft to the ground system using the GPS (Global Positioning System) satellites.

This is just an introduction to the concept of Multiplexer. To learn more about Multiplexers, read this Multiplexer (MUX) and Multiplexing tutorial.

Demultiplexer

Demultiplexer means one to many. A demultiplexer is a circuit with one input and many outputs. By applying control signal, we can steer any input to the output. Few types of demultiplexer are 1-to 2, 1-to-4, 1-to-8 and 1-to 16 demultiplexer.

Following figure illustrate the general idea of a demultiplexer with 1 input signal, m control signals, and n output signals.

Understanding 1-to-4  Demultiplexer

The 1-to-4 demultiplexer has 1 input bit, 2 control or select bits, and 4 output bits. An example of 1-to-4 demultiplexer is IC 74155. The 1-to-4 demultiplexer is shown in figure below-

The input bit is labelled as Data D. This data bit is transmitted to the selected output lines, which depends on the values of A and B, the control or Select Inputs.

When  A B = 0 1 , the second AND gate from the top is enabled while other AND gates are disabled. Therefore, data bit D is transmitted to the output Y1, giving Y1 = Data.

If D is LOW, Y1 is LOW. If D is HIGH, Y1 is HIGH. The value of Y1 depends upon the value of D. All other outputs are in low state.

If the control input is changed to  A B = 1 0 , all the gates are disabled except the third AND gate from the top. Then, D is transmitted only to the Y2 output, and Y2 = Data.

Example of 1-to-16 demultiplexer is IC 74154. It has 1 input bit, 4 control / select bits and 16 output bit.

Applications of Demultiplexer

1. Demultiplexer  is used to connect a single source to multiple destinations. The main application area of demultiplexer is communication system, where multiplexers are used. Most of the communication system are bidirectional i.e., they function in both ways (transmitting and receiving signals). Hence, for most of the applications, the multiplexer and demultiplexer work in sync. Demultiplexer are also used for reconstruction  of parallel data and ALU circuits.
2. Communication System – Communication system use multiplexer to carry multiple data like audio, video and other form of data using a single line for transmission. This process make the transmission easier.  The demultiplexer receive the output signals of the multiplexer and converts them back to the original form of the data at the receiving end. The multiplexer and demultiplexer work together to carry out the process of transmission and reception of data in communication system.
3. ALU (Arithmetic Logic Unit) – In an ALU circuit, the output of ALU can be stored in multiple registers or storage units with the help of demultiplexer. The output of ALU is fed as the data input to the demultiplexer. Each output of demultiplexer is connected to multiple register which can be stored in the registers.
4. Serial to Parallel Converter – A serial to parallel converter is used for reconstructing parallel data from incoming serial data stream.  In this technique, serial data from the incoming serial data stream is given as data input to the demultiplexer at the regular intervals. A counter is attach to the control input of the demultiplexer. This counter directs the data signal to the output of the demultiplexer where these data signals are stored. When all data signals have been stored, the output of the demultiplexer can be retrieved and read out in parallel.

This is just an introduction to the concept of Demultiplexer. To learn more about Demultiplexers, read this What is Demultiplexer (DEMUX) tutorial.

Conclusion

An introductory tutorial on Multiplexer and Demultiplexer. Learn the basics of Multiplexer, understand a basic 4-to-1 Multiplexer, applications of Multiplexer, Demultiplexer, a basic 1-to-4 Demultiplexer, applications of Demultiplexer.

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The 555 Timer IC is one of the most popular and most frequently used integrated circuits. It performs an array of timing tasks in the electronic circuits and there is a huge list of experiments which can be performed with 555 IC.  That is why it is very popular among electronics hobbyists.

But before using the 555 Timer IC, you should check it i.e. whether it is working properly or not. So, in this project, I have designed a simple circuit that can be used as a 555 Timer IC Testing Circuit and determine whether the 555 IC is functioning or not.

If you are stating with 555 Timer IC, then read this beginner’s tutorial on 555 TIMER IC.

A Brief Note on 555 Timer IC 

I won’t go into the details about the 555 Timer IC but a few important things you need to need before understanding how the 555 Timer IC Testing Circuit works. The first important thing is that the 555 IC is available in 8-pin Dual-in-line Package (DIP) (or atleast it is the one I will be using in this project). 

The second important thing about 555 Timer IC is that it has three modes of operation: Astable, Monostable and Bistable. The circuit implemented in this project is basically an Astable Mode of operation of the 555 Timer IC. 

Principle

This simple 555 IC testing circuit can be used to test your entire 555 timer IC collection. So, before using your IC in any project, make sure that your IC is good or bad by testing it. This can be done by configuring the IC to act as an oscillator i.e. 555 is configured in Astable mode of operation. 

The 555 tester circuit will rapidly tell you if the timer is functional or not. Important feature of this circuit is it will tell 555 timer is shorted or it is not oscillating. 

Simple 555 Timer IC Testing Circuit Diagram

The circuit diagram of the 555 testing circuit is shown in the image below.

Components Required

• 555 IC (IC under test)
• 8 Pin IC Holder
• 2 X 10KΩ Resistors
• 2 X 1KΩ Resistors
• 47μF Capacitor (Electrolytic)
• 0.01μF Capacitor (Ceramic Disc)
• 2 X LEDs
• 12V Power Supply 
• Mini Breadboard 
• Connecting Wires

Circuit Design

As mentioned earlier, I am going to use the 555 IC in its Astable Mode of operation. If you are familiar with this mode, then you can easily design the circuit yourself. 

First, connect Pins 4 (Reset) and 8 (VCC) to +12V Supply and Pin 1 (GND) to GND. Short Pins 2 (TRIG) and 6 (THRESHOLD). Now, connect a 10KΩ Resistor between VCC and Pin 7 (DISCHARGE). This resistor will be called R1. 

Also, connect another 10KΩ Resistor between Pin 7 and Pin 6. This resistor will be called R2. A 47μF Capacitor (here after called as C1) is connected between Pin 2 and GND. 

An optional connection is to connect a 0.01μF Capacitor between Pin 5 (CONTROL) and GND. Finally, connect two LEDs as shown in the circuit diagram to Pin 3 (OUT) of the 555 Timer IC.

How to Check the 555 Timer IC?

First of all, insert the IC in socket (if used) very carefully so that no pin of 555 timer gets damage. Now to see the result, switch on the power supply.  If your 555 timer is working properly, then both the LEDs (Red LEDs in my case) will glow alternately. If any of the LED is OFF or both the LEDs  are not glowing, it means that your 555 timer IC is faulty.

Working of 555 Timer IC Tester Circuit

In this circuit, I have used the 555 IC as an Astable multivibrator and when power is provided to circuit, the LEDs will start blinking, which means that the IC is working. The blinking rate of LEDs can be changed by increasing or decreasing the values of resistor R1 and R2 and capacitor C1.

You can calculate the time duration with the help of formulae given below.

ON Time (HIGH) in Seconds = 0.693 * (R1 + R2) * C1
OFF Time (LOW) in Seconds = 0.693 * R2 * C1
Total Time Period in Seconds = 0.693 * (R1 +2R2)*C1
Frequency = 1.44 / ((R1 + 2R2) * C1)

As per our circuit, R1=10KΩ, R2=10KΩ and C1=47μF. If you substitute these values in the above equations, you will get the following results.

Frequency = 1.023 Hertz
ON Time = 0.651 Seconds
OFF Time = 0.326 Seconds
Time Period = 0.977 Seconds

You can see this in the following video.

Now coming to working, as soon as power supply is provided, C1 will start charging through R1 and R2. When the voltage across C1 rises above 2/ 3 of supply voltage, the internal Flip Flop toggles. As a result, pin 7 becomes low and C1 starts discharging.

When the voltage across C1 goes below 1/ 3 of supply voltage, the internal Flip Flop resets and pin 7 goes high. The C1 starts charging again. All this will happen only when your IC is in good condition. Based on the charging and discharging times of the Capacitor (as set by R1, R2 and C1), the output will stay HIGH or LOW and the LEDs will flash accordingly. From these observations, we can conclude that 555 Timer IC is faulty or not.

Related Post: Touch ON and OFF Switch Circuit

The post How 555 Timer IC Testing Circuit Works? appeared first on ElectronicsHub.

Line Follower Robot Circuit Principle

This circuit mainly consists of 8051 microcontroller, two IR sensors, motors and motor driver IC (embedded in a module). The line follower robot needs mechanical arrangement of the chassis. I have used a 4WD Acrylic chassis. The two IR sensors are mounted on the fron of the robot facing with the diodes facing towards Earth.

When robot is placed on the fixed path, it follows the path by detecting the line. The robot direction of motion depends on the two sensors outputs. When the two sensors are on the line of path, robot moves forward. If the left sensor moves away from the line, robot moves towards right. Similarly, if right sensor moves away from the path, robot moves towards its left. Whenever robot moves away from its path it is detected by the IR sensor.

Do you know about How Remote Controlled Spy Robot Circuit Works?

IR sensor consists of IR transmitter and IR receiver on a board. When the vehicle is moving on a black line, IR rays are continuously absorbed by the black surface and there is no reflected ray making output high. Whenever, the robot moves out to the white surface, it starts reflecting the IR rays and making the output low. Thus depending on the output of IR sensor microcontroller indicates the motors to change their direction.

Line Follower Robot Circuit Diagram

Components in the circuit

• 8051 Microcontroller
• Development Board for 8051 Microcontroller (preferred)
• 10KΩ Resistors X 2
• 10µF Capacitor
• 11.0592MHz Crystal
• 33pF Capacitors X 2
• Push Button
• Motor driver Module (L298N)
• Robot Chassis with Motors
• IR Sensors x 2

How to Design a Line Following Robot?

 The circuit consists of 8051 microcontroller, IR Sensors (with IR transmitter and IR Receiver), L298N Motor Driver Module, Robot Chassis with 4 wheels and 4 motors, battery holder.

8051 microcontroller is the main component of the project. It is an 8 bit microcontroller with 32 programmable I/O pins. This has many peripheral features like programmable UART, two 8-bit timer/counter, two interrupts, external memory access etc.

 The DC motors of the robot are connected to the controller using a motor driver IC. As the output of the controller is maximum 5V with very small current, it cannot drive the motors. So, to amplify this voltage motor driver IC is used. L298N can drive motors up to 36v and can provide a drive current of 3A.

The driver IC has 15 pins and is usually available in multiwatt15 Package. These ICs are easily available in the market as Modules. The inputs to the Motor Driver Module are connected to PORT2 pins P2.0, P2.1, P2.2 and P2.3. 

The two IR sensors are connected to P2.6 and P2.7 pins of the microcontroller. Arrange the chassis and connect the four wheels of the robotic vehicle to the motors which are in turn connected to the microcontroller.

Related Post: DTMF Controlled Robotic Vehicle without using Microcontroller

Design of IR Sensors

IR sensor circuit consists of mainly IR transmitter and IR receiver. IR transmitter is similar to an LED. Its operating voltage is around 1.4V. So to protect it, a 150Ω resistor is placed in series with it and is connected in forward biased. IR receiver is connected in reverse bias and a 10KΩ resistor is placed between VCC and the receiver. Output is taken between resistor and IR receiver.

Since this is an analog output, we can convert it to a digital HIGH and LOW with the help of a simple comparator IC like LM358, for example. The IR Sensor Module used in this project uses the same configuration and the circuit diagram is shown below.

Working of IR Sensors

The IR transmitter continuously transmits the IR rays. When IR transmitter is on the black surface these rays were absorbed by the surface and when it is on white surface these rays were reflected. The IR receiver has maximum resistance when no IR rays are received and voltage from VCC flows through the resistor. At the output pin, voltage is approximately 5V.

As the intensity IR rays received by the receiver increases, resistance value decreases and reverse break down occurs. Thus voltage through the resistor is grounded. So, at the output pin, it will produce 0V.

Line Following Robotic Vehicle Circuit Working

1. Initially draw the path on a light colored surface with black color tape.
2. Place the robot on the floor.
3. Now power on the circuit.
4. Robot moves in the specified path.
5. When it moves out of path, sensors check it and automatically adjust the robot.

Code

Line Following Robot Circuit Applications

• This can be used in driver less car system with some added features like obstacle detection.
• This can also be used in industrial and defense applications.

Limitations of Line Follower Robot

• Line follower robot requires 2-3 inches broad line.
• It may not move properly if the black line drawn is of low intensity.
• The IR sensors may sometimes absorb IR rays from surroundings also. As a result, robots may move in improper way.

Note: If anybody interested on more robotics projects, visit the page: Robotics Projects

The post Line Follower Robot using Microcontroller appeared first on ElectronicsHub.

Introduction

Generally, in security systems that are used in homes, shops, offices, etc., infrared or laser transmitters and receivers are used for accuracy and reliability. But these methods require a lot of monetary investment and infrastructure support.

A simple cost effective solution for Security Systems is implemented in this project where I will explain about a PIR based Security Alarm System, in which a PIR sensor is used instead of transmitter or receiver. This saves power consumption as well as it is a low cost implementation. PIR sensor is the short form of Passive Infrared Sensor.

PIR Sensor based Security Alarm Circuit Principle

The main idea of the circuit is to provide security. This is based on PIR sensor with an IC that produces siren. The PIR sensor detects the IR radiations emitted from the humans and it produces a digital output. This digital output is applied to the Arduino UNO.

Based on the digital signal from the PIR Sensor, Arduino UNO then triggers the UM 3561 siren IC. Thus it produces the sound when any human is detected.

The UM3561 is a ROM IC. It generates multi siren tones like ambulance siren, fire engine siren, police siren, machine gun sound.

PIR Sensor based Security Alarm Circuit Diagram

NOTE: The circuit diagram shows the Oscillator Resistor (between Pin 7 and 8 of UM 3561) as 220Ω but it is 220KΩ. 

Circuit Components

• PIR sensor
• Arduino UNO
• UM3561 Siren IC
• NPN Transistor – 2N2222
• Resistors 10KΩ and 220KΩ
• Speaker 8Ω
• Breadboard
• Connecting Wires

PIR Sensor based Security Alarm Circuit Design

The designed system consists of Arduino UNO, PIR sensor, UM3561 IC, Speaker, transistor and a couple of resistors. The UM3516 IC is a Siren generator IC. It has 8 pins. First and sixth pins are the Sound effect selection Pins. Based on how they are connected, you can choose between 4 different types of sounds.

In this project, I have left open both the Pin 1 and Pin 6 to produce a Police Siren. Pin 5 is connected to +5V through an NPN Transistor (which is activated by Arduino UNO’s Pin 4).

One end of the 220KΩ resistor is connected to the seventh pin of the UM 3561 IC and the other end is connected to the eighth pin of the IC. Output is taken from the third pin of the IC and it is connected to a speaker through a resistor and transistor.

The base of the transistor is connected to the output of the IC through a resistor of 10KΩ. Emitter pin is connected to the ground while one end of the speaker is connected to the collector, while the other end is connected to +5V.

Coming to the PIR Sensor, its output is connected to Pin 3 of Arduino.

Code

Working of PIR Sensor based Security Alarm System

1. Make the connections as per the circuit diagram and switch on the circuit.
2. The PIR sensor is powered and it detects the IR rays emitted from any human.
3. This PIR sensor has a range of 5 meters. You can adjust the pot provided for the sensor to vary this distance.
4. When any human is detected, the PIR sensor outputs a logic HIGH value i.e. voltage of 3.5V to 5V to ARduino UNO’s Pin 3.
5. As soon as the Arduino detects logic HIGH on Pin 3, it makes the Pin 4 HIGH for a duration of 10S. During this time, the Siren IC UM3561 is activated as its Pin 5 provided with +5V.
6. The siren generator has an oscillator internally, to produce the sound.
7. The oscillator circuit is tuned to a certain frequency and using a 220KΩ resistor externally.
8. Then it is passed to the control circuit, which depends on tone selection pins.
9. These tone selection pins decide one tone from different tones produced by the IC.
10. Thus oscillations along with selected tone are sent to the address counter. The address counter then sends the data to the ROM.
11. ROM then sends the tone on the output pin 3.
12. The output is given to the NPN transistor to amplify the siren.
13. The base of the transistor gets voltage from output pin of the siren generator.
14. Transistor starts conducting when it gets the cutoff voltage at the base and the speaker is negative pin and is connected to the ground.
15. Thus sound produced can be heard from the speaker when human is detected.
16. In the present circuit, it produces Police Siren sound.

PIR Sensor Based Security Alarm System Applications

• This can be used in the museums to protect the valuable things.
• This can also be used as an automatic door bell circuit that rings the bell when human is detected.
• This can be used in defense applications to detect the humans in war field.
• This can be used in toy applications that produce sound.

Limitations of this Circuit

• PIR sensor pot should be adjusted in such a way to detect the humans only.
• This can detect the human only within its range of 5 meters.

The post PIR Sensor based Security Alarm System appeared first on ElectronicsHub.

Introduction

A frequency counter is an instrument that is used to measure the frequency of a signal. In scientific terms, frequency is the number of cycles per second of a signal. In layman terms, frequency of a signal denotes the rate of occurrence of the signal in certain time. Frequency Counters are basically simple counter systems with a limited time period for counting.

Here we design a simple frequency counter system using two timers and two counters. While one of the Timer IC is used to produce clock signals, the other is used to produce the time limited signal of one second.

Also Read the Post – Two Digit Up-Down Counter Circuit

Frequency Counter Circuit Operating Principle

This circuit is based on the simple definition of frequency, which is the number of cycles per second. Basically, a Square Wave Generator circuit is used to produce a simple pulse wave. These pulses are given as input to the Timer / Counter of the 8051 Microcontroller and count the number of pulses.

After performing some simple calculations, the resulting frequency is displayed on a 16X2 LCD Display in Hertz.

An important point to note is that I have used Arduino UNO as the source for Square Wave. You can use either Arduino or a completely build your own Square Wave Generator using 555 Timer IC by configuring it as an Astable Multivibrator.

Frequency Counter Circuit Diagram

Frequency Counter Circuit Design

As I have used Arduino to generate the Square Wave, all I need is a few lines of code and access to a single Digital I/O Pin. But if you are planning to build a Square Wave Generator circuit using 555 Timer IC, the understand the following explanation.

The primary requirement in the 555 Timer circuit is to generate an oscillating signal with a duty cycle of about 99% such that the time low value is less than the time high value of the output signal.  Since duty cycle depends only on the value of the threshold and discharge resistors, it can be adjusted by selecting the proper values of resistors.

The duty cycle is given by D = (R1+R2)/(R1+2R2)

Substituting the value of D to be 0.99, we get the value of R1 to be 98 times the value of R2. Thus, selecting a value of 100Ω for R2 and 9.8KΩ for R1. Practically the value of 10KΩ is chosen for R1.

Next step in the designing of the circuit is the design of the counter circuit. Here our requirement is the measurement of frequency of the order of few Kilo Hertz. As mentioned in the circuit principle, I will be using the Timer / Counter of 8051. In fact, I will be using both Timer 0 and Timer 1 of the 8051 Microcontroller.

I will be using Timer 0 to generate Time Delay and Timer 1 to count the Pulses coming from the pulse generator. Timer 0 is configured as Timer in Mode 1 while Timer 1 is configured as Counter in Mode 1. 

Do you about the concept – Bi Directional Visitor Counter using 8051 Microcontroller

Code

Following is the code for Frequency Counter Circuit using 8051 Microcontroller.

Frequency Counter Circuit Operation

Make the connections as per the circuit diagram and apply the Pulse generated by Arduino at Port 3 Pin P3.5, which is the Timer 1 Pin. As I have configured the Timer 1 as counter, using the TCON Bit TR1, I will be counting the pulses for a duration of approximately 100 milliseconds by making TR1 HIGH and LOW. The count of the pulses is stored in Timer 1 i.e. in TH1 and TL1 Registers.

To get the value of the frequency, you have to use the following formula.

frequency=(TH1*256)+TL1;

In order to convert the Frequency Value to Hertz i.e. Cycles per Second, you need to multiply the resultant value by 10. After this, the resultant value is formatted by performing some simple mathematics so that it will be easy to display the result on the 16X2 LCD Display.

Applications of this Circuit

1. The Frequency Counter Circuit using 8051 Microcontroller can be used to accurately measure the frequency of a signal.
2. Since we are counting pulses, we can measure the frequency of only square waves and its derivatives (with different duty cycles.)

The post Frequency Counter Circuit appeared first on ElectronicsHub.

Introduction

Turn Indicator Lights also known as Directional Indicators (formally) or Blinkers, Flashers (informally), are an essential part all automobiles whether a bike or a car. They inform other road users our intent to turn left or right. There are several regulations and standards that manufacturers must comply with while designing and integrating Turn Lights on to a vehicle.

Bike Turning Signals are used to indicate the intent of left turn or right turn to other users of the road. Have you ever tried to design bike turning indicators? This article explains you how to design these bike turning indicators.

Bike Turning Signal Circuit Principle

The objective of this circuit is to indicate left or right turn for bike/vehicle. The main component of this circuit is the infamous 555 Timer IC. Here, this 555 timer acts as an Astable multi vibrator. It generates the pulse signal with variable width. Using this variable width of the pulse, we can set different time delays for the LEDs (ON and OFF for LEDs).

The circuit consists of two important resistors (100KΩ and 470KΩ), which are connected to 555 timer and these are used to set the time delay for LEDs. The output of the 555 Timer IC is given to either LEFT indicator LED or the RIGHT Indicator LED using a Slide Switch. 

1n4148 signal diode is connected in reverse bias at the output to maintain constant current at the output. BC547 (NPN) Transistor switches the LED’s ON and OFF based on the base currents. 330 ohm resistors are used to drop the voltage otherwise LEDs may get damaged. Here we can vary the time width of output pulse by varying the resistance or capacitance value.

Bike Turning Signal Circuit Diagram

Circuit Components

• Resistor 180Ω
• Resistor 100KΩ
• Resistor 470KΩ
• Capacitor 1µF
• 555 Timer IC
• LEDs – 2
• Diodes (1N4007) – 2
• SPDT Slide Switch
• 9V Battery
• Connecting Wires
• Breadboard

Bike Turning Signal Indicator Circuit Design

In this circuit, the 555 timer produces pulse signal with variable width. The pulse width is varied by varying resistance or capacitance value (100KΩ, 470KΩ or 1µF). Pins 2 and 6 are shorted to allow triggering after every timing cycle.

Fourth pin is reset, it is shorted with VCC (8^th pin) to avoid sudden resets. 7^th pin is discharging pin, it is connected to 6^th pin through a 470KΩ resistor. The below figure explains you the operation of 555 timer. In this circuit capacitor C charges through resistors RA and RB. Now because of internal op-amps, capacitor C discharges through resistor RB. 555 timer internally consist of 2 operational amplifiers, one D flip flop and one NPN transistor.

In the above circuit, the pulse is generated at the 3^rd pin of the 555 timer. By varying the values of RA, RB or C, we can vary the pulse width. The total time period of the pulse is given as

T = T_HIGH + T_LOW = 0.693 (R_A+ 2R_B) C

 Frequency of the pulse is given as

f = 1/T = 1.44/ (R_A+ 2R_B)C

percentage of duty cycle is given as

% duty cycle, D = t_c / T * 100 = (R_A + R_B) / (R_A + 2R_B) * 100

The obtained pulse from the 555 timer is applied to the LEDs through the slide switch to make the LEDs ON and OFF with some delay. Here the operating voltage of LEDs is around 2 to 3v but from battery, we get 9V supply. So, we need to drop the remaining voltage. To drop this voltage, we are using resistors in series with LEDs.

How to Operate the Circuit?

• Initially feed 9V power supply to the circuit.
• Slide the switch to the Left position and you can observe the LEFT Indicator LED will start to Blink with some delay.
• If you slide the switch to Right Position, the RIGHT Indicator LED will Blink.
• If you slide the switch to center, both the LEDs will be OFF
• If you want, set the different time delays for LEDs, then vary the resistance or capacitance value.
• Now you can see the change in time delay.
• By varying the capacitance value also you can see the in time delay of LEDs.

NOTE: Since this is a demonstration, I have used only one LED per channel (LEFT and RIGHT). But if you want to integrate several LEDs per channel, you can do that with the help of a Transistor on each channel and sufficient power supply.

Applications of Bike Turning Signal Indicator Circuit

• It is used to indicate left turn or right turn for a motor bike or vehicle.
• We can also use this circuit as an LED knight rider circuit.
• We can give it as a gift for the children.

The post Bike Turning Signal Circuit appeared first on ElectronicsHub.

Introduction

There can be any sudden situation of panic. It could be because of an intruder entering our house or bad health status. Situations can be many for panicking and may vary from person to person.

During such emergencies, we might be unable to intimate to the people around us. In this article we shall see how to make a simple panic alarm, which can help us to intimate others regarding our bad situation without any delay.

Panic Alarm Circuit Diagram

Components Required

• 555 IC
• Resistor – 1KΩ
• Resistor – 22KΩ
• Resistor – 100KΩ
• Capacitor – 10µF
• 9V Battery
• Push Button
• Mini Buzzer
• Breadboard
• Connecting Wires

Design

This circuit is made with a low cost hardware using IC 555 timer, buzzer, a few resistors and capacitors. It is made to be working reliably as it has simple to use and not so sensitive hardware like 555 timer, ceramic buzzer, capacitors, etc.

Although no exclusive arrangement is used to make any compensation for the variable parameters, the circuit by default is made to be robust and easy to use. It is very user friendly with a single button to be pressed to handle the panicking situation without any trouble.

Also get an idea about Working of Burglar Alarm Circuit

Working

The IC 555 is used in the Astable mode with the frequency depending on the values of resistors R2, R3 and C2. The values of R2 = 100KΩ, R3 = 22KΩ and C2 = 10µF.

By substituting the given parameters in the respective formulas for IC 555 in astable mode, we get the following values. The frequency of operation of the circuit is calculated to be 1 Hz. By finding the time period of the circuit by using the frequency information, we get the time period of the circuit as 1 second. This means the circuit has a on -off repeating time period of about 1 second.

After analyzing the ON and OFF time period of the panic alarm circuit given above, we find that the circuit will remain on for about 0.845 seconds and off for about 0.152 seconds.

The circuit is in the disabled mode when the button is not pressed and hence the alarm will not function when the button is not pressed. Although the power supply will be supplied to the IC 555 all the time, the circuit will operate in the astable mode only when the IC is enabled. The IC is in the enable mode only when pin 4 of the 555 IC is given a high voltage.

This happens only when the button is pressed. The button can be made to have a plastic enclosure to have a better visibility and ease of access to it. For the purpose of demonstration, I have connected a simple Buzzer to the output of the 555 IC. 

Also Read the Post: Thermistor Temperature Sensing Alarm

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WARNING: This project is not for beginners as it involves AC Mains supply. Make sure that you have an adult / expert supervision if you are planning to implement a similar project.

Introduction

Today, fluorescent bulbs (mercury filled Compact bulbs or tube lights) are becoming outdated and they are being replaced by LED lights. One of the main reason for this is LED lights consume less power and have long life in comparison to fluorescent lamp and tube light. LED lights have many advantages over Fluorescent lamp and are mentioned at the end of this post.

Here, we have described a simple circuit which you can easily made and install in your homes and will not only save resources but your energy and money will also be saved.

Also Read the Post: Battery Powered Portable LED Light Circuit

Mains Operated LED Light Circuit Diagram

Components used in this Circuit

• Bridge rectifier – 1
• Resistor (R1) – 1MΩ
• Resistor (R2) – 560Ω / 1W
• Capacitor (C1) – 0.22uF / 400V)
• LEDs – 5
• Breadboard
• Connecting Wires

Mains Operated LED Circuit Explanation

This simple circuit is based on simple components: Bridge rectifier, resistors, LEDs and capacitor. All the components used in this circuit are easily available in market. So you can make this circuit and install in your homes and offices. Before understanding the working of circuit first have a look on the component description.

Rectifier

A rectifier is an electronic circuit used for converting alternating current (AC) to direct current(DC). And the process of converting alternating current to direct current by allowing one way electron flow is called as rectification. In full wave rectifier four diodes are connected in a circuit to form a bridge. In this approach, we are utilizing both positive and negative cycles of AC.

A bridge rectifier contains four diodes D1, D2, D3, D4 connected to form a bridge as shown in figure. Hence this arrangement is known as a bridge rectifier.

Working of Bridge Rectifier

The AC signal to be rectified is applied to the diagonally opposite ends of the bridge through the transformer. Between another two ends of the bridge, The load resistance R_L is connected.

During positive half cycle of secondary voltage, The end P become positive and end Q negative. Thus Diode D1 and D3 will become forward bias and start conducting , while diode D2, D4 are reversed bias.

Diode D1 and D3 are in series with the load resistance R_L hence current flows through R_L as shown in figure.

During negative half cycle of secondary voltage, the P end becomes negative and Q end become positive. Diode D2 and D4 are forward biased hence they start conducting . Whereas diode D1 and D3 are reversed biased.

Diode D2 and D4 are in series with the load resistor R_L hence current flows through R_L  as shown in figure. It may be seen that again current flows from A to B through the load i.e. in the same direction as for the positive half cycle. Thus DC voltage is obtained across load R_L  . Output waveform of a bridge rectifier is shown in figure below. The advantage of Bridge rectifier is that its output is higher than of full wave and half wave rectifier.

LED

Light emitting diode are different  from other diodes as they emit light and hence referred as light emitting diode. LED are available in RED, GREEN, BLUE color.

Resistor

All material have some type of opposition to the current flow. This opposition is called resistance. The resistance of a material is determine by the number of free electrons in the material. There are various type of resistor available such as carbon film, carbon composition, filament resistor and many more which can be used in an electronics or electrical circuit to determine the resistance.

Resistance of circuit depends upon p, L and A with the following equation.

R = p*(L/A)

Capacitor

The capacitor is a device that store electrical energy and capacitance is the amount of electrical energy stored at a given voltage drop by capacitor. A device specially designated to have a certain value of capacitance is called a capacitor. The capacitor has the ability to store electrons and release them at later stage. The capacitor is generally consist of two metal plate which are separated by a non conducting material called as dielectric.

Diode

Diode is an electronic device which allows current to flow only in one direction. Diodes are forward by joining N type and P type semiconductors. The N type semiconductor contains free electrons that move through the material. Similarly P type semiconductor contains holes. Electrons from the N type which are near the junction cross the  junction and fill in the holes in P type material. Similarly holes near the junction of  P type material, crosses the junction and occupy the place of electrons. A depletion layer is formed at the junction of the PN semiconductor.

Mains Operated LED Light Circuit Working 

Working of circuit is very simple. Assemble the circuit properly as shown in circuit diagram. Now apply AC mains. Resistor R2 is used as current limiting component and resistor R1 is used with capacitor C1 so that it will discharge the capacitor which prevents lethal shock.

Now this power supply is provided to the bridge rectifier circuit which will convert the AC to DC and also reduces the voltage with the help of current limiting components. Now this power supply is passed to LEDs and the LED connected at the output start glowing. You can use bridge rectifier available in market or you can make your own with the help of four diodes. Maximum you can use up to 20 LEDs.

Advantages of LED Bulbs

• LED bulbs have 10 times longer life in comparison to fluorescent and incandescent lights.
• LED bulbs does not contain filament so there is less chances of damage.
• Common incandescent bulb become hot and generate lot of heat in the room while LED bulb prevents the heat build up and helps in reducing the air conditioning cost in room.
• Power consumption of LED lamp is approx. 2-17 watt 1/3 in comparison to fluorescent lamp. So if you LED bulb you can save much on your electricity bill.
• As power consumption of  LED lamp is very less, use in solar panels is increasing.
• Many people are using inverters in their home and now they are using LED lights with inverters because this will also increase the time period for which inverters can support LED light.
• Initial cost of LED bulb is more in comparison to fluorescent bulb with they have long life and they can be easily move from one place to another without breakage and save electricity also. Therefore LED bulb is more efficient than fluorescent bulb.
• LED bulbs are not sensitive to temperature or humidity.
• LED bulb does not contain mercury also hence do not provide harm to environment also.
• LED lights will turn on instantly.

Also read the following posts to know more about LED circuits:

• Bi-Color LED Dancing Lights
• Auto Intensity Control of High Powered LED

The post Mains Operated LED Light Circuit appeared first on ElectronicsHub.

Introduction

One of the main advantages of LEDs over traditional light bulbs is that an LED can be easily controlled i.e. we can easily change its intensity. You might have already used light dimmers but this LED Lamp Dimmer Circuit is a very simple circuit where a bunch of LEDs continuously change its intensity.

By making slight modification with respect to the power dissipation, you can even implement this circuit with high-power LEDs for real-time use.  

LED Lamp Dimmer Circuit Diagram

Circuit Components

• IC LM358 (IC1) – 1
• Transistor BC547 (T1) – 1
• Resistors (R1, R2) 4.7KΩ – 2
• Resistor (R3) 22KΩ – 1
• Resistor (R4) 10KΩ – 1
• Resistor (R5) 4.7MΩ – 1
• Resistor (R6) 100Ω – 1
• Capacitor (C1) 0.47µF – 1
• LEDs – 3
• 9V Battery
• Breadboard
• Connecting Wires

Component Description

LM358

This IC consists of two independent, high-gain, frequency-compensated operational amplifiers designed to operate from a single supply over a wide range of voltages. Operation from split supplies also is possible if the difference between the two supplies is 3 V to 32 V (3 V to 26 V for the LM2904), and Vcc is at least 1.5 V more positive than the input common-mode voltage. The low supply-current drain is independent of the magnitude of the supply voltage.

Transistor

A three terminal electronic device employed to amplify weak input signals. A transistor made up of two PN junction diode linked back to back. Transistor are of many type viz bipolar junction transistor, Field effect transistor and photo transistor. They are mainly used in electrical machine as of their lesser size as well as light weight.

LED

LED stands for Light Emitting Diode. It is made up of semiconductor device. When power supply is provided to LED, electrons combines with the holes and energy  is released in the form of light. LED are available in  many colors like Red, Orange, Amber, Yellow, Green, Blue and White.  Now-a-days, LED’s are available in visible, ultraviolet and infrared wavelengths and have high brightness.

Working of LED Lamp Dimmer Circuit

LM358 is mainly made up of a package which contains two independent operational amplifiers of high gain. The most significant attribute of this IC is that we need not provide independent power supply for the functioning of each comparator till the large range of the power supply. LM358 can be employed like transducer amplifier or can be worked as DC gain block etc.

The DC voltage gain of the LM358 IC is huge i.e. 100db. Coming to the power supply, this IC can work on the voltage range of 3V to 32V while for the twin power supply this IC work on the range of ±1. 5V to ±16V. And moreover large output voltage is also supported by it.

Related Post: PWM LED Dimmer Using NE555

Pin configuration of the IC LM358 is being described below.

To get a triangle wave an op-amp is used in the circuit that has been explained here. It is only due to the triangular wave that the LED starts glowing slowly and became brighter and then slowly  gets off and again it becomes brighter slowly. The same cycle goes on repeat many of the times.

In each independent op-amp of the package, there are two input pins and one pin as the output, as it shown on the figure above. Pin 2, which is a negative pin and pin 3, which is the positive pin are the two input terminals of the op-amp. For the positive feedback pin 3 is used and if there is a desire of the negative feedback pin 2 is used. When there is no feedback given to the op-amp than at that state infinite gain, is the ideal condition for the op-amp.

When the voltage at pin number 2, which is a negative input pin, is higher when compared with the voltage at pin 3 i.e. a positive pin, then the output will be received towards maximum positive voltage while if there is a slight boost at the negative pin of the op-amp as compared with the positive pin of the op-amp than the output moves in the direction of the negative maximum. This characteristic of op-amp craft it appropriate for the use of level detection.

The voltage level which we want to detect is applied to either of the input pins and the voltage to be detected is applied to the other pin. In our circuit, we are applying a voltage on positive pin that is at pin 3 and voltage to be detected is applied at negative pin.

At the instance when the input voltage given to the positive pin is a little more than that of the voltage given at the negative pin, at that condition the output rapidly mounts to the positive maximum and reside in the positive state till the input voltage drop lower than the level to be detected.

The same phenomenon is being used in this circuit too. For the timing component resistor R5 as well as capacitor C1 is used. State of the pin 3 switches from high to low condition depending upon the charging and discharging of the capacitor used in the circuit and as a reference to it pin 2 of the op-amp obtains the desire output. For the driving of the LED transistor T1 is used in the circuit as a signal amplifier and to protect the LED from the damage due to high current resistor R6 is employed in the circuit as a current limiter.

The post LED Lamp Dimmer Circuit appeared first on ElectronicsHub.

Introduction

Police Lights are flashing lights which are a type of emergency vehicle lighting. You can also find similar flashing lights in ambulances, fire department, military vehicles etc. They are visually captivating and often convey the state of urgency of their task to the other road users.

In this project, we will just take the visual aspect of the police lights and implement them in our own way. The circuit uses 555 timer and a decade counter IC CD4017. Here, the 555 timer runs in Astable mode. Decade counter 4017 counts the incoming pulses  and activates its outputs i.e. for the first pulse Q0 becomes high and for second pulse Q1 becomes high and so on again for 10th pulse Q0 state becomes high.

555 Timer Based Police Lights Circuit Principle

Here 555 timer produces continuous pulses via pin 3. The width of these pulses can be varied by varying the resistance (R1,R2 ) or capacitance (C1). These pulses are given as input to the decade counter. For every incoming pulse the output state of the decade counter is get incremented.

• For 1st pulse – Q0 high – blue led’s glow
• For 2nd pulse – Q1 high (no connection) – all led’s off
• For 3rd pulse – Q2 high – blue led’s glow
• For 4th pulse – Q3 high – all led’s off
• For 5th pulse – Q4 high – blue led’s glow
• For 6th pulse – Q5 high – red led’s glow , blue led’s off
• Hence blue led’s flashes for 3 times.
• For 7th pulse – Q6 high – all led’s off
• For 8th pulse – Q7 high – red led’s glow
• For 9th pulse – Q8 high – all led’s off
• For 10th pulse – Q9 high – red led’s glow
• For 11th pulse – Q0 high – blue led’s glow, red led’s off

Hence, red LEDs flash for 3 times. This process repeats continuously.

Do you know – How to Build Police Siren Circuit using NE555 Timer?

Circuit Diagram of Police Lights using 555 Timer

Circuit Components

• 555 Timer IC
• 4017 Decade Counter IC
• 1KΩ Resistor (1/4 watt) – 3
• 22KΩ Resistor (1/4 watt) – 1
• 470 ohm Resistor (1/4 watt) – 6
• 2.2µF Electrolytic capacitor (16V) – 1
• BC547 NPN Transistors – 2
• Blue LEDs – 2
• Red LEDs – 2
• 9V battery – 1
• Connecting wires

555 Timer based Police Lights Circuit Design

555 Timer

Here, 555 timer runs in free running mode i.e. Astable Mode. It produces pulses whose width can be varied. 2nd and 6th pins are shorted to allow triggering after every cycle. 4th pin is connected to Vcc to avoid sudden resets.

4017 Decade Counter

It is a 10 bit counter with ten decoded outputs. It counts the incoming pulses. The supply voltage range is -0.5 to +22V. The high pulse on the reset pin clears the count to zero. The speed of operation of this IC is up to 10 Mhz.

The ouput states (Q0,Q2,Q4) are configured to flash the blue LED’s 3 times and the states Q5, Q7 and Q9 are configured to flash the red LED’s 3 times.

Based on the outputs of 4017 IC, two transistors (NPN) switches the LED’s ON and OFF.

Resistors R3, R4, R5, R6 are used to protect the LED’s from high voltage.

Circuit Simulation Video

How to Operate Police Lights Circuit?

• Apply power to the circuit.
• Now observe the LED’s, red led’s flashes 3 times and blue led’s flashes 3 times and this process repeats.
• If you want to set the different time delays for LED’s then vary the resistance (R1, R2) or capacitance (C1).

555 Timer based Police Lights Circuit Applications

• This circuit used as an indicator for police cars.
• We can use it as LED flasher circuit by making some modifications.

Limitations of Police Lights Circuit

• The values of the resistors R1, R2 and capacitor C1 should be same to get perfect flashing.

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