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.
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 circuit can be used in kitchen or inside your PC. If your kitchen appliances or PC are over heated, it may be possible that it will damage the expensive components present in it. So to protect them from damage we have described a simple circuit which will give an indication when temperature around the sensor increases above the level set by you. This circuit is very small and can be easily install. In short, this simple project with easy to build electronic circuit is very useful to fight with problems like overheating.The circuit is based on two IC and few more discrete components.LM35 is a precision integrated circuit temperature and its output voltage is linearly proportional to centigrade temperature.IC CA3130 is operational amplifier which combines the advantage of both CMOS and bipolar transistor on a single chip.
Everyone has studied this rule in their childhood. It stands for “bracket, “off”, “division”, “multiplication”, “addition”, “subtraction”. A mathematical operation involve a number of operators but they must carry out in a particular order. The circuit described here will help you to practically implement the BODMAS rule which we have studied.The circuit is made with the help of three IC’s namely 7404, 7408 and 4073. 7404 is a hex inverter or NOT gate IC. It is a 14 pin IC and contain 6 individual NOT gate on a single IC. 7408 is a quad 2 input AND gate IC. It contains 4 individual AND gate on a single IC. 4073 is a triple 3 input AND gate. It contains 3 individual AND gate on a single IC. LED, switches and resistors are also used in this circuit.
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.
The performance of each and every electronic system or electronic circuit depends upon the power supply that energizes the circuit or system. It provides required current to the circuit. Any disturbance noise in this power supply can cause problem in working or operation of circuit. If there is any deviation in this power supply level the circuit may not work properly. The accuracy and precision of circuit operation depends upon it. In some of the circuits all the calibration are done at this voltage level. So all these calibrations becomes false if there is fluctuation in supply level. There are two types of power supplies: Unregulated power supply, Regulated power supply. Unregulated supply is used in some circuits where there is no much change in required load current. The load current remains fixed or deviation is very less. Read more to know about this interesting power supply project.
Seven segment displays nowadays are commonly used in place of dot matrix display. They have found their use in places like microwave or fancy toaster oven or the same on washing machine but before using them in all these places you need to interface the 7 segment display with microcontroller or some more hardware will be required. But with the basic knowledge of 7 segments display you can use it in front of your shop or you can display your name on it. 7 segment displays numbers from 0 to 9 and some alphabets.7 segment display are labelled a to g and decimal point is usually known as DP. DP is the common point. In common cathode display they are connected to ground and rest pin are connected to supply. Similarly in common anode DP are connected to supply and rest are connected to ground. You can also use more than one display according to your requirement.
The electronics devices works in dc power supply comes with different voltage specifications. Some devices works in battery power with voltages ranging from 1.5V to 9V, but majority of the devices can be directly plugged into a power plug. Such devices have a built in AC to low voltage DC converter inside it and the voltage output of that converter will be corresponding to the design of the entire circuit. The design of a circuit actually begins with considering the value of the voltage which will be supplied to it.The circuits which work in 5V power supply are most common which contains 5V TTL devices, but there is other category of TTL devices which works in 3.3V supply. Apart from these two categories there are CMOS based circuits and there is all kind of analog circuits which are designed to work on different voltages. Those who are interested in working with all these kind of circuits should have a variable power supply source.
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.
The 8-LED Flasher is built around Timer and Counter ICs. It Flashes 8 LEDs sequentially and the flashing speed can be controlled by a potentiometer. This can be used as a design pattern for decoration. But theoretically, it clears the Timer and Counter concepts in an easy way.The circuit comprises of various components like 555 Timer IC, Decade counter (CD4017), LEDs, Resistors, Capacitors, Wires & a 9V battery. The monolithic integrated circuit 555 timer can be used as square-wave generator, linear saw-tooth generator, pulse generator, time delay generator, etc. here we use it to generate square waveform i.e. it is used in the Astable Mode with a duty cycle of 66.6%.The 8 LEDs could be arranged in any pattern and thus be used as a decorative Light Toy in your living room.
There are times when it is difficult to judge the distance while reversing the car or while parking. If someone is there to help you that is great but in situations when you are driving alone then what will you do? Or you are a new driver and cannot judge the distance? This circuit will solve all these problems. You can easily install at the back side of your car. Operated at 5V power supply and can also recharge batteries. You can also use them as shadow alarm at doors to protect your car. When shadow of a intruder fall on it will also give you alarm. This alarm will provide you the musical sound that’s why it will not tease your ears. Main components of this circuit areLM358 IC, LDR, UM66 IC, speaker and few more discrete components.LM358 consist of two independent, high gain operational amplifier in one package. Important feature of this IC is we do not require independent power supply for working of each comparator for wide range of power supply.
You might have seen so many applications and circuits based on monostable multivibrator using IC555 like intruder alarm, automatic night lamp, smoke detector, fire alarm, automatic gate controller, object counter etc. In all such circuits monostable multivibrator is used. We may easily understand the operation of the circuit but many of us don’t know how such circuits are designed. So here I will try to explain how such circuits are designed using some examples.To detect the light we need any photo sensor and the LDR is one of the most convenient photo sensor. It works on photo conductivity principal. That means its resistance varies as light falls on it. In absense of light the resistance of LDR is maximum and as light intensity increases the resistance decreases. So we can use this property in designing this circuit. As the resistance of LDR changes, the voltage across it also changes and this voltage is used to trigger monostable multivibrator.
The circuit developed here will count the number of visitor entering or exiting from door of auditorium or hall or any other place. Depending on the interrupt from the sensors, the system identifies the entry and exit of the visitor. On the successful implementation of the procedure, it displays the number of visitor present in the room. Therefore it can be economically implemented in all the places where the visitors have to be counted and controlled. This circuit is good enough for only one person entering at a time. It will also give you visual indication of circuit with the help of LED. It is operated at wide range of temperature from 5V to 20V. The big advantage of the 4026B counter IC is that it can drive a 7-segment display without needing a decoder driver IC. It will count the number of visitor up to 99 which can be increased by cascading more 4026 IC.
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.
This circuit confuses the infra-red receiver in a TV. It produces a constant signal that interferes with the signal from a remote control and prevents the TV detecting a channel-change or any other command. This allows you to watch your own program without anyone changing the channel!! The circuit is adjusted to produce a 38 kHz signal. The IR diode is called an Infra-red transmitting Diode or IR emitter diode to distinguish it from a receiving diode, called an IR receiver or IR receiving diode. (A Photo diode is a receiving diode). There are so many IR emitters that we cannot put a generic number on the circuit to represent the type of diode. Some types include: CY85G, LD271, CQY37N (45¢), INF3850, INF3880, INF3940 (30¢). The current through the IR LED is limited to 100mA by the inclusion of the two 1N4148 diodes, as these forms a constant-current arrangement when combined with the transistor and 5R6 resistor.
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).
Water level controllers are quite common nowadays. This circuit is based on popularly used IC555 IC. Water level controller circuits have these advantages: Most the circuit only display the amount of water present in circuit, but this circuit will “on” and “off” the motor according to the level of water present in tank. It will not automatically stop the motor when tank is fill but it will “on” the motor when water in tank reaches below a specific point. It can be easily installed in over headed tanks because of less components used in circuits. It prevents the wastage of water due to over flow of tank. Can be operated with the help of 12V battery or adaptors (converts 230V AC to 12V DC) readily available in markets.
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.
CD4033 is 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. Means it will convert the input into numeric display which can be seen on 7 segment display or with the help of LED’s.
This is very much interesting application and I think you will surly build it. Any battery powered toy car can be made to run or stop from a remote place (around 100 mts) using this remote. Because it is RF remote you can operate your toy car through the obstacles (like wall, partitions etc.). So it will be a real wireless control for toy car.
This is single chip remote because transmitter and receiver are made up of single chip SM5021B and SM5032C respectively. Both chips are perfectly design for IR remote system by “Samhop microelectronics corp.”. It is an 8 channel remote with 2 inbuilt on/off controls & 6 pulse outputs. Before starting the project first go through the datasheets of both ICs.