Anjali Sethiya

In this project a protoype circuit which can switch on the device when the light falls on it. For this I will use LM358 IC which is operational amplifier. I have made the circuit with LDR and few more components. But when I interchange the LDR with photodiode, phototransistor and transistor (L14F1) my circuit works well without changing any other components. Before understanding the circuit which I have developed, first let’s have a look on the components used in the circuit.LM358 consists of two independent, high gain operational amplifiers in one package. Important feature of this IC is that we do not require independent power supply for working of each comparator for wide range of power supply.  LM358 can be used as transducer amplifier, DC gain block etc. 

  Heat sensor senses the heat present around the sensor. When temperature rises above the set value, it will indicate the presence with the help of glowing LED. This heat sensor circuit can be used in kitchen or inside your PC. If your kitchen appliances or PC are over heated, it may be possible that…

This simple circuit will act as a warning alarm whenever the temperature of a device exceeds above the safety level.  This circuit can be used to monitor the heat built inside the devices like your PC, inverters, CD player etc. As excessive heat may affect the sensitive component and may lead to permanent damage. The main advantage of this circuit is its compactness that’s why it can be easily install in the device itself. This circuit will also give you power on indicator of a device with the help of blinking LED. Therefore it attract your attention that device is on. This circuit uses a negative temperature coefficient (NTC) as a sensor to sense the heat. This circuit can be operated on wide range of temperature vary from 5V to 12V. 

In 1910 Frank W. Wood made a board which can display number and after several modifications today it’s called 7-segment display. It is available in two configurations: common cathode and common anode. All the 8 LED terminals have their one end internally shorted and linked with the middle pins such that it serves as a common terminal (cathode or anode). 7 led are used to form the digits while the 8thone is for the dot which helps in identifying the correct orientation. It is widely used in digital clock, calculator, electronic meters and various other applications where numerical display is required. It can be used in place of dot matrix displays which are more complex than seven segment display. Seven segment displays can also be used to display some alphabets. Seven segment displays is a group of Light emitting diode (LED) arrange in figure of 8 pattern.   

Relay is a very important device now days. They are used in various circuits and many of us have problem of how to use a relay. With the help of this article I have tried to explain two things firstly the Working of relay and secondly how to use a relay. As we know relay is a device which is used to provide connection between two or more points or device in response to the input signal applied.  In another words relay provide isolation between the controller and the device as we know devices may work on AC as well as on DC. However, they receive signals from microcontroller which works on DC hence we require a relay to bridge the gap. Relay is extremely useful when you need to control a large amount of current or voltage with small electrical signal. 

Are you ready to make your first project? If the answer is YES then you are at the right place to learn all the basics about building your project. So let’s start: Before making a new project, you require some basic tools and knowledge of how to use them to complete your project. Most important and commonly used tool which you require is soldering iron and soldering wire. You will also need some more tools like wire-cutters, wire-strippers and a pair of small pliers. Some other tools are also useful although they are not essential at starting stage. If you are beginner or doing soldering for first time, we will suggest you to use solder iron of power rating between 15-25 watts which is suitable for most of the soldering work. Higher watt soldering iron is also available in market. Keep in mind higher wattage iron does not mean that it will melt the solder wire fast. 

Many of us design PCB with the information available on internet but sometimes it becomes difficult to understand the terms used in designing. In this article I have tried to explain the common terms which are used while designing PCB. PCB stands for printed circuit board. Different types of PCB materials are available in markets. Most commonly used are FR-1, FR-2, CEM-3, CEM-1 (FR=Flame Retardant and CEM= Composite Epoxy Material).Everything which you draw is on layer. Each layer has different physical properties. For example top layer is used to draw the component layout, bottom layer or inner layer are used for making connection between components and many more are also present. 

Different kinds of PCB design software’s are available in market and according the requirement different users used different software. Like I am comfortable in designing my PCB on Eagle and my vendors who fabricate the PCB does not have Eagle than what will happen? Hence to bridge the gap between the PCB designer and manufacture we use gerber file. Gerber file contain information about the PCB like what will be the pad size, drill size, name of component etc. With the help of gerber file information obtained and manufacture feed the data into their machinery to manufacture PCB. The most common format that is used today is RS-274-X. But before using always check with the board manufacture. It is a good practise to check your layout before manufacturing because once it has been fabricated you cannot correct your mistake. Or it may happen that PCB will not be of any use this will lead to wastage of time and money both.  

This circuit can be used in various projects where we require the counting. Like in doctors’ clinic or hospitals, in restaurants, in customer care offices where long queue is there and we want to stop the rush at the counter. This system is very effective where man power is less. In this you have to provide a token to the person and the person has to wait for its turn which can be displayed on the 7 segment display. With the help of this circuit we can maintain the silence and the person will also be informed about their turn.This circuit is based on 4026, a Johnson counter IC commonly used in digital display. It has a 5 stage Johnson decade counter with decoder which convert the Johnson code to a 7 segment decoded output 

I am designing a circuit which can be controlled by  TV or AC remote. For that I have purchase TSOP1738  with few more components from market. And I assemble my circuit carefully, then also I am not getting the desire output. I again rechecked my assembled circuit with the circuit diagram and I don’t find…

CD4033 is a Johnson counter IC commonly used in digital display. It has a 5 stage Johnson decade counter with decoder which converts the Johnson code to a 7 segment decoded output. This means it will convert the input into numeric display which can be seen on 7 segment display or with the help of LED’s.Advantage of this IC is it can be operated at high voltage of 20V because it is highly sensitive and it can detect EMF presence in the atmosphere and it is sensitive to static charge also.When you touch the input terminal with finger, counter get’s started.Therefore care should be taken while using it. It can be used in various applications like in 7 segments decimal display circuit, in clocks, timer etc. 

This circuit will light up different LED’s according to the audio signals which are feed through condenser microphone. When sound intensity is low few LED’s will glow as intensity of sound increases number of LED’s which glow also increases. Important feature of this circuit is we have not use any special running light IC like LB1405. We have made this circuit with the help of seven channel Darlington array IC ULN2003. ULN2003 is a monolithic high voltage and current Darlington transistor array. It contains seven NPN Darlington pair on a single IC. It also have high output voltage with common cathode clamp diode for switching inductive load. And collector current rating of each Darlington pair is 500mA.  Another feature of ULN2003 IC it has 2.7kW series base resistor for each Darlington pair so that it can directly connected to TTL or 5V CMOS device. Read more to find out how this circuit is assembled and how it is made to work. 

This circuit is based on two commonly used IC that is NE555 timer and CD4017 IC with few more components. 555 timer IC wired as an monostable oscillator. In this circuit NE555 monostable generates a clock for the circuit, which provide a oscillating wave to the output pin 3 of IC1.  Monostable or one short multivibrator has only one stable state and we have to trigger it externally to return it back to its original state. CD4017 is a CMOS counter/ divider IC . It take clock signal from the clock input and turn on the 10 output in sequence, each time when it receives clock input pulses. It is the most popular IC and extremely useful in various project like Light Chaser, Matrix Die. In order to understand the working of IC one must know about its individual pin. 

This multipurpose adjustable timer circuit will give you alarm after every specific interval of time. You can vary the time interval with the help of 8 way dip switch. Therefore this timer can be used in kitchen, or by students preparing for competitive exam. As many of us have habit to forget, to switch off button of gas, electric oven which lead to wastage of resources and your hard work. Now with the help of this circuit you will receive an alarm after specific time so that you can remember to off the device. Some other features of the circuit are: You can also use it as alarm to switch off the motor because while watching TV or talking over phone we forget to switch off the pump in that case also it will give an alarm. You can set the time period for coking also like we used to in microwave oven. 

Many times it happen when somebody comes home in night and press the door bell, We search for the porch light switch.  To identify that the visitor who as press the door bell is known or unknown person before opening the door. This circuit will help you to solve the problem.  When a visitor press the doorbell switch it will automatically on the porch light after sometime so that when you reach near the door you don’t have to search for light switch. This circuit will automatically off the light after some time. This circuit also has the facility to on the porch light from inside the house. In day time you can off the light with the help of switch S3. Doorbell cum light has inbuilt doorbell so you do not require to purchase a door bell. 

While driving car, Before taking a turn it is a good practise to use the indicator, which will not only alert the other vehicle driver nearby you but reduces the chances of accident as well. But if your vehicle indicator is not working well then you can use this simple circuit. In night many accident took place because of less traffic, high speed and casual driving. We forget to use indicator and speeding vehicle behind you or from opposite side does not get time to slow or stop their vehicle. Therefore the use of indicator is always required in driving and while turning. This small circuit can also be used for two wheeler even in bicycle. Main advantage of this circuit is, it will not only give a visual indicator but also give you a buzzer sound while turning left or right. 

Logic high and low indicator is used to measure the voltages (high and low). For measuring the logic state high or low just put the probe on that point and you get the display on 7 segment display.  This circuit will display “H” if voltage is high and it will display “L” when voltage is low. This simple circuit is based on 555 timer which act as a bi-stable multi-vibrator and two common anode seven segment display used as indicator to display logic state and few more discrete components. In bi-stable mode 555 timer act as a basic flip flop. We have club the pin 2 and 6 that is trigger and threshold pin and the voltage which is to be measure must be applied on this pin. When this pin 2 is low, circuit is in set position and changes the output state to high. And when pin 2 is high output pin 3 is low. It will hold the state either high or low indefinitely that is why it is called bi-stable multi-vibrator. We have connected the pin 4 with the switch which is used to reset the circuit. Pulling the reset input to ground acts as a ‘reset’ and transitions the output pin to ground (low state). 

The circuit described here stops the musical sound when darkness is detected like when you put your hand above the sensor. This circuit can be used as morning alarm. Install it on your window so when the light falls on it will start giving you melodious sound to wake up. In night you can use it to switch off the light of staircase. When you switch off the light of your room with little modification like you can connect relay at output (in place of speaker) to off the bulb. This circuit can be operated with pencil cell as it require less only 3V for its operation. It can easily be mounted because of number of components used in circuit are quite small. LDR is a device whose sensitivity depends upon the intensity of light falling on it. 

The doorbells produce a ringing alert sound so that the resident comes to know that there is somebody at the door. Many homes have two doors for entering. So, sometime it become confusing for the resident to find out on which door visitor is  present. This project on doorbell circuit produces two different sounds and can be used simultaneously on both the doors. This circuit also gives a visual indicator so that deaf person can also know. For this we use different color LED for different door so that it becomes easy to know whether the visitor is present on front door or rear door. This simple circuit is based on transistor, diode, resistor and switches with few more components. Resistor is a two terminal passive component used to control the flow of current into the circuit. 

The project described below is a small model of traffic light which we daily see in our life on street. With this circuit you can control two way traffics. There will be lights on both sides, like there is red light on one side and green light will be present aautomatically on another side. It will also have yellow light to alert the passengers or drivers that now there signal are going to open.CD4017 is a 16 pin CMOS decade counter/ Divider.  It take clock signal from the clock input and turn on the 10 output in sequence, each time when it receives clock input pulses.4072 is a dual 4 input OR gate. Output of OR gate goes high when any of the input goes high and if all input is low then output is also low7432 is a quad 2 input OR gate. In this also output goes high when any of the input is high and goes low when all inputs are low. 7432 contains 4 individual OR gate on single IC.