The 21st century belongs to portable devices that are run by batteries. From smartphones and laptops to smart home and office appliances, the new electronics devices are compact in size, more power efficient, loaded with multiple features and run on supply provided by batteries. These electronic devices usually have components like diodes, transistors, capacitors or ICs having such components embedded in them which are polarized in nature.So the electronics circuit of these devices essentially must be provided DC power is a specific polarity. Any battery has two terminals – Anode and Cathode and current always flows from anode to cathode. Actually, the electrons flow from cathode to anode.
As the popularity and use of smartphones and tablets have grown, the demand for portable and hands on power supplies have also increased. The smartphone and tablets come with a battery which gets discharged in 4 to 5 hours of use. As a solution to this problem, power banks have been introduced in the market for the frequent users. These power banks also come to resort when the user is on a long journey and has no facility to charge up his phone or tablet. A power bank is basically a portable device which can supply power to the gadgets like smartphones and tablets through the USB port. Power bank itself can be charged by USB port and stores charge which later can be used to power up other devices.
In this era of portable electronics devices, most of the electronics run on batteries. A battery stores the charge and then supply that charge to power up any electronics device. The use of batteries require its own kind of precautions and handling. A major problem with the use of batteries is their over discharging and over charging.Both of these issues affect the life of a battery and cost the end user needlessly. These issues are often ignored by the consumers too. Since batteries do have nice price tags, it ultimately add up the maintenance cost of any electronics device. In this electronics project, a zener diode based circuit will be designed to protect a battery from over discharging. When a battery is charged, its terminal voltage i.e. voltage between the anode and cathode of the battery increases.
Most of the modern devices are run by the batteries. A battery stores the charge and then supply that charge to power up any electronics device. Though batteries are handy to use, their use need some precautions too. A major problem with the use of batteries is their over discharging and over charging. Both of these issues affect the life of a battery and cost the end user needlessly. These issues are often ignored by the users too. The improper handling of batteries shorten their life and may even lead to explosion. This ultimately increases the maintenance cost of the electronics devices.
Many times, there is need to step up or step down DC voltages. The circuits for stepping up or stepping down DC voltages are not simple as is the case with AC voltages. The level changing of DC voltages requires complex circuitry. These circuits are called DC to DC converters. The DC – DC converters are the electronic circuits which convert a constant DC voltage to a high voltage level or to a low voltage level.When a circuit increases the DC voltage to a higher level, it is called Boost Converter. When a circuit decreases DC voltage to a lower level, it is called buck converter. Since a boost converter converts the DC voltage to the higher voltage level, it is also known as step-up converter. For boosting the voltage signal a regulator circuit is required which can step up the input voltage signal.
There have been never so extensive use of batteries before. The portable electronic devices are growing more and more popular and these devices are all run on batteries. With the use of batteries, over charging and over discharging are common problems. In order to avoid over charging and over discharging of batteries, it is required to keep track of the charge level of the attached battery. A circuit used for such purpose is called battery level indicator. A battery level indicator gives the indication about the battery charging or discharging state. Secondly, some batteries have high tolerance limit for overcharging and some may explode after a certain limit of charging. That is why it is important to disconnect the battery from charging when it reaches its maximum limit.
LM317 is commonly used for voltage regulation in DC circuits. The IC is one of the popular adjustable positive voltage regulators that comes with features like over voltage protection, internal current limiting, overload protection, low quiescent current (for more stable output) and safe area compensation (its internal circuitry limit the maximum power dissipation so it does not self-destruct). Apart from many features, less number of components are required to make it operational.
In the previous projects, adjustable power supplies and constant voltage symmetrical power supplies were made. In this project, an asymmetrical power supply will be designed. The triple bench power supply acts as a power source providing three different constant voltages. The different voltage levels are drawn using a single transformer. The triple bench power supply designed in this project gives 5V, 9V, and 12V at the output with 1A as the maximum current limit for each voltage. The output voltages are regulated supplies independent of the unwanted fluctuations in the input voltage. The power circuit designed in this project uses 7805, 7809 and 7812 voltage regulator IC to output 5V, 9V, and 12V regulated supplies.
In the previous projects, the power source used was the AC mains. In this project, the solar energy will be tapped using a solar panel and it will be regulated to charge a 3.7 V battery. The 15 Watt solar panel used in the circuit has a DC output voltage of approximately 22 V. The DC output from the solar panel is not regulated and needs to be made ripple free using a voltage regulator.Once the voltage drawn from the solar panel is regulated to desired levels it can be utilized for powering load circuits. In the project, the regulated voltage is utilized to charge a battery. The project involves deriving DC voltage from the solar panel, regulating input voltage, voltage adjustment, and back current protection.
AC to DC conversion is an essential step in power circuit design. Generally step down transformers are used for AC to DC conversion. But the use of a transformer makes the circuit bulky. There is no replacement of transformers when current requirement of the load circuit is high. However when low currents are needed to be drawn by the load circuit, X-rated non-polarity capacitors can also be used for AC to DC conversion. These kind of power supplies are called capacitor power supplies or transformer less power supplies.
The power supply circuit designed in this project is a voltage doubler. A voltage doubler generates a voltage twice of its input voltage. So, this power supply circuit provides maximum 23V at the output with an input voltage of 11.5V. The circuit is designed by using a 555 IC with some diodes and capacitors. The capacitors help in providing the doubled voltage at the output compared to input voltage. The capacitor stores charges from the input voltage and transfer it to the output in such a way that twice of the input voltage is obtained at the output.The important sections of the circuit designed in this project include stepping down AC voltage, converting AC voltage to DC voltage, Smoothing DC voltage, Compensating transient currents, short circuit protection and voltage doubling using 555 IC and capacitors.
In the previous projects, a capacitor for smoothing AC to DC converted signal was used. The purpose of using the filtering capacitor was to protect the load circuit from any fluctuations and ripples in the input voltage. The fluctuations or ripples are quite common when the circuits are powered ON and switched ON or OFF suddenly. In this project, a more robust circuit to handle input fluctuations is designed. The circuit is built using OPAM and SCR. It is used to operate a relay which controls the supply to the load. A rectified 12V supply is assumed at the input of the circuit and same voltage without ripples will be obtained at the output.
A constant current source is used to provide a constant current regardless of the input voltage and output load. These type of circuits are also used as a current limiter. Most electronic devices have a maximum current rating and if current above that rating is drawn by it, the device may get damaged or not work properly. Therefore a lot of times constant current power supplies are required to operate electronic devices. In this project, an adjustable constant current source which supplies 25 mA constant current at the output regardless of load resistance and the input voltage is designed.
In the previous tutorial, a Bass Boost Power Amplifier was designed. Now it’s time to start designing power amplifiers suitable for specific applications. In this tutorial, a car audio amplifier will be designed. The cars have been coming with inbuilt audio systems from years. An audio system of a car is one of the important features that shines as unique selling point (USP) for any car in the market. The audio systems have become a vital accessory for any car. Even many times consumers replace the default audio systems came in their car with new one for better driving experience.
Continuing with the designing of application specific power amplifiers, in this tutorial a low power amplifier will be designed for regular mobile headphones. In the previous tutorial, a car audio amplifier using TDA2003 IC was designed. The mobile headphones are a type of miniature speakers designed especially for use with smart phones. These headphones do not have louder sound output. However, their sound quality can be improved by using an amplifier circuit with them. For headphones, a low power amplifier need to be designed.
In the previous tutorials, the amplifier circuits to boost audio from a single channel were designed. Over the last decade, there is growth in the audiophile. This has brought a revolution in the music industry. Now, people like to hear the high resolution surround music just like a 3D video. A surround sound system is designed to create a sound field like the sound is coming from back, front, left and right sides. It can also create the sound above the listener. The surround sound system is used in cinemas and drama theaters to give a realistic feeling to the audience.
In all the previous tutorials, power amplifiers were designed. On the basis of application, there are two types of audio amplifiers – 1) Pre-Amplifier2) Power Amplifier The pre-amplifiers are used to level up the audio signals from a microphone or audio source to standard voltage levels while the power amplifiers are generally used at the output stage of the audio systems to boost audio signals before they are reproduced by the speakers. As the name suggests, a Pre- amplifier prepares the signal which is coming from the microphone or line input for further processing and transmission of the signal. A preamp is the hidden part of any device. It is integrated in the USB microphones, sound cards and mixers.
In all the previous tutorial, a pre amplifier using MAX4468 was designed. On the basis of application, there are two types of audio amplifiers – 1) Pre-Amplifier2) Power Amplifier The pre-amplifiers are used to level up the audio signals from a microphone or audio source to standard voltage levels while the power amplifiers are generally used at the output stage of the audio systems to boost audio signals before they are reproduced by the speakers. As the name suggests, a Pre- amplifier prepares the signal which is coming from the microphone or line input for further processing and transmission of the signal. A preamp is the hidden part of any device. It is integrated in the USB microphones, sound cards and mixers.
The open loop buck converter designed in the previous tutorial did not had a regulated output. The output voltage was varying with the resistance of the load. The output of the circuit designed in the previous tutorial could be regulated by adding a feedback circuit in it. The feedback circuit could help in error detection of the output voltage and change duty cycle of the frequency on which circuit operates to provide a constant output voltage irrespective of the load resistance. Contrary to Linear Regulators which step down the DC voltage by dissipating the heat, Buck Converters step down the DC voltage through switching regulators and also step up the output current. According to the law of power conservation, input power must be equal to output power.
The designing of Boost Converter SMPS has been already discussed in the previous tutorials. In this tutorial, an open loop buck converter SMPS will be designed. The Buck Converter is also one of the topologies of the SMPS (Switched Mode Power Supply). These type of SMPS steps down the DC voltage unlike the Boost converters step up the DC voltage. So the buck Converter is also a DC to DC step down converter in which the output voltage is always less than the input voltage. Contrary to Linear Regulators which step down the DC voltage by dissipating the heat, Buck Converters step down the DC voltage through switching regulators and also step up the output current.