The foundation of Raspberry Pi is an educational charity located in the UK. The main intention of this foundation is to develop the education system for children and adults, especially in the field of computer science related subjects. The Raspberry Pi is a credit-card sized and low-cost device. It plugs into a TV or computer monitor and uses a mouse and keyboard. This device allows all the students and aged people to learn how to write a program in a language like Python and Scratch. This Raspberry Pi is mainly used for browsing the internet, playing HD video, word pressing, playing games and to make spreadsheets. The applications of Raspberry Pi mainly involve in digital projects, music machines, weather stations, IR cameras and raspberry pi projects.
Generally, the LDR is a photocell and it works on the principle of photoconductivity. A resistor is a passive component whose resistance is decreased when the intensity of light decreases. In the light varying sensor circuit, the optoelectronic devices are used mostly. The LDR is a device which is made up of high resistance semiconductor material. Some of the applications of LDR are street lights, clock radios, light alarm, reflective smoke alarm, outdoor clocks, and camera light meters. In this article, we will discuss the working & construction of light dependent resistor.
What is a Light Dependent Resistor?
The light dependent resistor (LDR) is designed with the highest resistance semiconductor metal. If the light falls on the device, then the photons produce the electron energy and it makes them bound into the conductive band. Hence it conducts electricity. The LDR circuit is also known as photo resistors. Here we will see the symbol of the LDR.
Working of Light Dependent Resistor
Here we are discussing the most common & simple working principle of the LDR. The working principle of the LDR is based on the photoconductivity and it is an optical phenomenon. The material conductivity is increased when the light is riveted by the material. If the light falls (photons) on the device, the electrons which are in the valence band of the semiconductor material are moved to the conduction band. These photons in the occurrence, the light will have the energy greater than the bandgap of the semiconductor material to move the electrons to valence band to the conduction band.
Therefore, therefore the light will strike the sufficient energy on the device and there is more electrons are eager to the conduct, therefore, the result will be in a large number of charge carriers. Hence the result of this process, when the circuit is closed more current is flowing through the device and the resistance of the device is decreased.
Construction of LDR
The construction of the light dependent resistor consists of light sensitive material which is deposited on an insulating substrate like a ceramic. To get the desired resistance & power rating the metal is deposited in the pattern of zigzag. This zigzag pattern separates the metal deposited areas into two regions and on both sides of the pattern the Ohmic contact is prepared.
The resistance of the contacts is very less to make sure that the resistance, mainly changes due to result of light. Generally to construct the light dependent resistance materials are used like cadmium sulfide, cadmium selenide, indium antimonide and cadmium sulphonide. The utilization of lead and cadmium are neglected because they are very destructive to the environment.
Circuit Diagram of Light Dependent Resistor
The light dependent circuit is an electronic circuit and the components required to build the circuit are LDR, relay, Darlington pair, diode and resistor. The voltage supply is set for the load and the necessary DC voltage of the LDR circuit is from the battery or a bridge rectifier circuit. The step down transformer is used in the bridge rectifier circuit and it transforms the voltage from the 230V to 12V.
In this circuit the diodes connected with the bridge form and it is used to alter the AC voltage into DC. To change 12V DC to 6V DC the voltage regulator is used and to the entire circuit the 6v DC is supplied. From the two bridge rectifiers 230V is supplied and the load is kept continuously in constant operation of the light sensor circuit.
The light sensor has low resistance in the morning time of 100ohms. Therefore the power supply passes through the LDR & ground through the variable resistor. Due to this, the resistance exists by the light dependent resistor in the daytime or when the light fall on the LDR, therefore it is comparatively very less to the resistance of the remaining parts of the circuit. As we know the principle of current, that the flow of current always flow in the path of low resistance.
Thus, the relay coil will not get enough supply to get strengthen. Hence the light is switched OFF in the day time. In the same process in the night time the resistance of the LDR increases to 200Mohms. Therefore, due to the high resistance of the resistor, the current flow is low or almost zero. In the low resistance the flow of current increases with the base voltage of Darlington pair to get more than 1.4V. Therefore the Darlington pair transistor is triggered with the relay coil obtain sufficient supply to get energized. Hence the light glows in the night times.
Characteristics of LDR
The LDR’s are light dependent devices and the resistance is decreased when the light falls on the light dependent circuit. If the LDR is in the dark room, its resistance is very high and it is called as a dark resistance. The light dependent resistance is high as 1012 ohms and if the device is permitted to absorb light its resistance will be decreased completely and if a constant voltage is applied to it. The intensity of light is increased, the current will increase. The following graph represent between the resistance and illumination curve for a LDR.
Applications of Light Dependent Resistor
- The price of the LDR is very less and it is very simple in structure
- In the light sensor the resistors are used frequently
- These resistors are used to sense the presence & absence of light like alarm circuits, alarm clock, light intensity meters and etc.
Advantages of LDR
- The price of the LDR is less and there are different sizes & shapes which are available in the market
- In the practical LDR there are different sizes are available and the most popular size is 100mm phase diameter
- For the operation of LDR it requires less power and voltage
Disadvantages of LDR
Extremely they are inexact with the reaction of time about tens, hundreds of milliseconds.
In this article we have discussed about tutorial on light dependent resistor and its applications. I hope by reading this article you have gained some basic information on the LDR working. If you have any queries about this article or about the electrical projects for engineering students, please feel free to comment in the below section. Here is the question for you, what are the functions of the light dependent resistor?
The comparator plays an important role in the electronic circuit design. Types of comparators are categorized into several kinds, namely electronic, electrical, optical, mechanical, sigma, pneumatic and digital comparators. Comparators play a vital role in making electrical and electronic projects. In electronic circuit design, an operational amplifier is used with negative feedback and it can also be used as a comparator. The designing of the comparator can be done without feedback for open loop formation. These are used widely in analog to digital converters. When the input signal is sampled, then the signal is applied to numerous comparators to change the digital form from the analog form. The comparator applications involve in zero crossing detectors, BLDC operating motors, switching power regulators and also in peak detectors. This article gives an overview of different types of comparators and its applications.
In digital electronic projects, the encoder and decoder play an important role. It is used to convert the data from one form to another form. Generally, these are frequently used in the communication systems like telecommunication, networking, and transfer the data from one end to the other end. In the same way it is also used in the digital domain for easy transmission of data, placed with the codes and then transmitted. At the end of the receiver, the coded data are collected from the code and then processed to display.This article discusses about what is encoder and encoder, working and its applications.
The breakdown diode is an electrical component which will have the two electrodes. The two electrodes are anode and cathode. Most of the diodes are made up of semiconductor materials like silicon and germanium etc.The basic property of the diode is to conduct the electrical current in only in one direction and block the current which is in the opposite direction. If the cathode is negatively charged which is related to the anode next to a voltage is greater than the minimum is called as the forward breaker and the current flows in the diode. If the cathode is positive with respect to the anode, it is negative by an amount less than the forward break over voltage, hence the voltage does not conduct the current. The switch and diode characteristics are similar to each other and the earlier semiconductor device was the crystal detector and used in the wireless radio.
Security is a major concern in our daily life. Everybody desires to be as much safe as possible. The progressive home security system has improved to the present security system in our day-to-day life. Security systems for homes protect from the thief. Security systems are protected in the home keeps the things safety from the thief, hazardous events in our home surrounds. The security in the home has to start the owner of the home and to look after the home. The finest way to guard the home is by connecting the security system in the home These systems are classified into two types, namely wired security system, and wireless security system. Nowadays, most of them are using a wireless security system. It is simple to use and threatened by the unknown person. The wireless security systems are motion sensor detector, camera, etc. The home security systems are normally used by the motion sensor and monitor detector, that are placed in unknown places.
The electronic world is developing every day gradually. The change of voltage is the basic principle involved in many of the circuit devices. The Voltage has to be changed from higher to lower and from lower to higher, inverting, rectification etc. with all these it is impossible to run a circuit. In this article we will be converting 6V to 12V DC converter circuit, where the first DC is converted into AC which is called inverting and again converting AC to DC it is called rectification. We will be discussing everything in detailed with a basic circuit diagram and every point is written in a simple way to understand very quickly.
6V to 12V DC Converter Circuit
The 6V to 12V DC Converter Circuit mainly includes DC to AC conversion, AC to DC conversion which is discussed below.
DC to AC Conversion
In many of the applications it is required to convert from DC to AC. This is mainly used in places like camping, on roads where Stereo or TV is used or other appliances are required. The inverter which converts DC to AC will resolve this problem. Here it 12 VDC and steps it up to 120 VAC. Basically the wattage of the circuit depends on transistors which are used for Q1 and Q2, and also choosing of the transformer size T1. The inverter can be constructed to supply anywhere from 1 to 1000 watts.
The Parts of the circuit shown below.
- C1, C2 68 uf, 25 V Tantalum Capacitor
- R3, R4 180 Ohm, 1 Watt Resistor
- D1, D2 HEP 154 Silicon Diode
- T1 24V, Center Tapped Transformer
- R1, R2 10 Ohm, 5 Watt Resistor
- Q1, Q2 2N3055 NPN Transistor
- MISC Wire, Case, Receptacle
The wattage of inverter supply determined by Q1 and Q2, as well as the T1.
By using T1= 15A and Q2, Q1=2N3055, the inverter is capable of supplying around 300 watts. For more power T1, Q1 and Q2 are used like a substitute for larger transformers and more powerful transistors.
To get large T1 the easiest and least expensive ways rewinds an old microwave transformer. These are the transformers which are rated at about 1KW and also perfect. The bigger the microwave the bigger transformer. Now remove the transformer, and be careful not to touch the existing large high voltage capacitor which might be still charging. Remove the old 2000 V secondary of the transformer, and ensure not to damage the primary. Leave the primary intact. Now, the next step would be to wind on 12 turns of wire, twist a loop, and again wind on 12 more turns.
The gauge of the wire will generally depend on how much current you plan to have the transformer supply. For the security and safety wind with tape. For the transistors Q1 and Q2 it is to be remembered that they require high current. The 2N3055’s can only handle 15 amps each.
It is important to note that while operating at high Wattages, this circuit draws a huge amount of current which may lead to battery dead. Here a fuse is included in this project produces 120 VAC. The capacitors C1 and C2 should be tantalum. Electrolytic will overheat and explode.
AC to DC conversion
Rectification is the process of converting AC to DC. Thus the application used in many of the devices. AC voltages will be very dangerous.
Most of the consumer electronics goods will regulate from AC mains to DC. The circuit shown above will have a large transformer. It is made of several steel plates i.e. Sandwiched and then epoxies together, and two or more windings of coated copper wire. Each winding can be of few to several thousand turns. The no of windings basically determines the change in voltage.
Whenever a current is introduced through a winding or coil, it will create a magnetic field, and then poles will be formed along the winding axis. If another coil is placed nearby, along the same axis, the magnetic field will induce a current, and thus a voltage is induced in the second coil.
This adding of magnetic permeable core between the two greatly enhances the effect, reducing loss. These two windings can be wrapped on one another since they are insulated. It will lead to space saving and a very efficient. Several windings are added for separate windings to get desired voltages. Computer power supplies are sufficient. The output desired will be AC.
The magnetic coupling to work here the magnetic field must change polarity. By using AC current, it is possible to switch between negative and positive voltages at 50-60Hz. The electronic circuits to work, it must be stepped-down AC voltage to a flat, stable DC voltage.
Now here comes the bridge rectifier into action, and in this case a full-wave rectifier is used. Here switch the negative AC pulses to positive pulses, and will leave the positive pulses. Some voltage loss will take place due to the voltage requirements of the diodes. The final result would be a pulsed DC voltage, going from 0 to maximum voltage at 120Hz. We use a capacitor across the ‘-‘ and ‘+’ terminals to smooth out the ripples.
When the voltage rises from 0 to the max, the capacitor starts charging. When the voltage drops, the capacitor starts to discharge through the circuit, but in a slower rate, holding the voltage up while the supply drops to 0 and then rises again. When the capacitor charges to its value, it surges back to max again. Less rippling is formed because larger capacitors will allow the voltage to stay higher. The full – wave rectifier is better here than a half – wave rectifier, since there is less time between the high and low pulleys, will result more stable output.
This article is Simple 6V to 12V boost converter circuit using BD679 transistors. The power supply circuit uses the simple 6V to 12V boost converter circuit using BD679 transistors. To get DC voltage 12V here we have 6 volts only the circuit can modify DC voltage 6 Volt be 12VDC.
|1||R2, R3||2||4.7K 1/4W Resistor|
|2||R1, R4||2||2.2K 1/4W Resistor|
|3||R6||1||1.5K 1/4W Resistor|
|4||R5||1||1K 1/4W Resistor|
|5||R7||1||33K 1/4W Resistor|
|6||C1,C2||2||0.1uF Ceramic Disc Capacitor|
|7||R8||1||10K 1/4W Resistor|
|10||C3||1||470uF 25V Electrolytic Capacitor|
|11||Q3||1||BD679 NPN Transistor|
|12||D3||1||12V 400mW Zener Diode|
|14||Q1, Q4, Q2||3||BC547 NPN Transistor|
|15||MISC||1||Heat sink for Q3, wire, board, binding post|
The principle works of the circuit is Q1, R1, Q2, R2, R4, R5, D1, R3, C1 and C2 build the circuit is model astable multi-vibrator gives output as a square Wave, which gives a positive pulse signal at high frequency Here R6 perform to limit the current already flow and will reach at a pin B of Q3 and a pin C of Q4 in this condition, the current flow come to the pin B of Q3 make Q3 bias. But Q4 still not yet bias. This is because of still there is no current bias at a pin B. When Q3 is biased it makes the current flow through L1, D2 change ZD1 by causing drop voltage at ZD1.
When the voltage increase continually which will be equal to 12 volts? Now R7 will limit the current, where change comes in the way pin B of Q4. When Q3 stops biasing then Q4 starts to work. Now output voltage will be 0 volts, but when the positive pulse signal is sent to R6 then again it makes Q3 bias again. To appear the output at 12 volts all the time it can be achieved by using capacitor C3. It filters the current smoothly before increasing lead output voltage before it is used.
This article 6V to 12V DC Converter Circuit Explanation with Circuit diagram is explained with DC to AC, AC to DC, and consolidates explanation of both together along with their respective circuit diagrams. I hope everything is understood clearly with the above explanation. If there is anything yet to be clarified and you feel anything is missing or to implement any electrical and electronic projects, please feel free to comment in the below section. I will be certain helping you. Here is a question for you, what is switch mode power supply?
Home inverter is an electrical device used to give the power to the electric appliances in the event of the power failure. The name inverter implies first changes alternating current to direct current to charge the battery then, it inverts direct current to alternating current for powering the electric devices There are different types of Inverters are available in the market. The most proficient inverter is the pure sine wave which produces an alternating current like to the domestic power supply in wave form. Generally, the low cost types of inverters mainly include Square wave & quasi sine wave. But, less efficient than the pure sine wave inverter because some electric machines will not work properly in these inverters. Now, solar powered inverters are very famous to conserve energy, but the cost will be very high as it needs a very large solar panel.
An inverter is a motor control that adjusts the speed of an AC induction motor. It does this by varying the frequency of the AC power to the motor. An inverter also adjusts the voltage to the motor. This process takes place by using some intricate electronic circuitry that controls six separate power devices. They switch on and off to produce a simulated three phase AC voltage. This switching process is also called inverting DC bus voltage and current into the AC waveforms that are applied to the motor. This led to the name “inverter”. For the rest of this discussion, the term “inverter” will be used in place of adjustable speed drive.
The transistor amplifier which escalates the power level of the signals will have the audio frequency range is called as a transistor audio power amplifier. The practical amplifier contains a number of stages which will amplifies weak signals until required power is existing to activate the output device like loud speakers. In some stages the multistage amplifier will have the functions of voltage amplifier, hence the maximum power is in the last stage is called as the power stage. The basic block diagram of the audio amplifiers is given.