This is attained by adding two resistors R1 and R2 as shown in figure. Circuit diagram. C1 is the filter capacitor the thumb rule is uF per amp at Hz. For 2 amps 50Hz is uF. C2 is a HF decoupling capacitor to avoid HF instability. C3 is for reducing the output impedance of the power supply such that no instability in the connected load due to power supply common impedance effect.

The power supply here is only 9V output. If you used a V supply then you will get all the voltages mentioned in the article. Even if you get the voltages out after inputting 12V plus, the whole idea of boost is defeated, especially when the current this contraption will eck out is a measly ma or less. This article is misleading. Sorry bro. It gives 3. I think they are enough.

variable power supply circuit

Ckt is checked 5 times. Help needed guys. Author john. Regulated DC power supply October 7, How to fix the values of the capacitors? What is their use? Seetharaman 6 years ago. Hi Jov 25volts will do. Pat 7 years ago. Vikas dabas 8 years ago. Submit Type above and press Enter to search. Press Esc to cancel.Have you ever tried to design a variable regulated power supply? This article describes you how to design a variable power supply circuit.

Till now we have seen a lot of power supply circuits, but the main advantage of this power supply circuit is that it can vary the output voltage and output current. For smaller voltages, we normally use batteries as a reliable source. Instead of using batteries, which have a limited lifetime, a variable DC power supply can be used which is implemented in this project. It is a robust, reliable and easy to use variable DC power supply. The working of the circuit is as follows.

A transformer is used to step down the AC supply to 24V at 2A. A bridge rectifier is used to convert this voltage to DC. Depending on the settings of the POT, the ADJ pin of LM receives a small portion of the output voltage as feedback and the output voltage is varied.

With the help of this variable DC power supply, the output voltage can be varied from 1. This circuit can be used as reliable DC source and acts as a replacement to batteries.

It is important to attach the voltage regulator IC LM to a heat sink as it tends to get hotter during operation. The above circuit uses only 15 v transformer at the input,so it can be varied maximum upto 15V. Although the voltage regulator LM protects the circuit from overheating and overload the Fuses F1 and F2 are used to protect the power supply circuit.

The rectified voltage at capacitor C1 is around So we need to use all the capacitors which are rated at 50v in the circuit. Pot RV1 allows us to vary the output voltage in between 0 to 28V. The minimum output voltage of LM voltage regulator 1.

In order to get 0V at the output we are using 3 diodes D7, D8 and D9. Here 2N transistors are used to get more current. Pot RV2 is used to set the maximum current available at the output. LM is the 3 pin series adjustable voltage regulator.

This regulator provides output voltage ranging from 1. This IC is easy to use and requires only two resistors to provide the variable supply.In this post we learn how to make a simple variable power supply circuit using transistor 2N and some other passive components.

variable power supply circuit

It includes variable voltage and variable current feature, fully adjustable. A power supply circuit that does not include the features of a variable voltage and current control can by no means be considered truly versatile.

How to Regulate Amps and Voltage_ 200ma to 5Amp_5volt to 30volt

A variable workbench power supply circuit explained in this article is not only specified with a continuously variable voltage control but is also equipped with the feature of overload or continuously variable current control. The voltage variations are made by using the preset P2, through a feedback configuration employing the components D1, R7, T2 and P2. The inclusion of D1 makes it sure that the voltage can be lowered right down to 0. If any other specific minimum value is required then the diode can be replaced by zener diode having the required specified value.

Variable power supply using 7805

Therefore in this variable power supply circuit using 2N transistor, the transformer being a 0 — 40 V, the output becomes variable right from 0. The value of R4 is specifically becomes responsible for defining the maximum allowable output current. If you have any doubts regarding this variable voltage and current power supply circuit using transistor 2N circuit please do not hesitate to ask then through the comments below. The above design was inspired from the following circuit which was designed and presented in the elektor electronics magazine by the elektor engineers:.

The above designs were assessed and simplified with more effective results by Mr. The revised and simplified design can be viewed in the following diagram:. PCB Design for the above Circuit. William C. The key highlights of the circuit are: wide range output: 0. In addition, higher extension of the output range becomes feasible through the inclusion of T4 between the IC and the series pass transistor.

T3 works like an output current controller. When P1 is rotated totally anti-clockwise, T3 restricts at 0. The limiting circuit becomes inactive when P2 is moved completely clockwise.

The regulator circuit specifically operates in the following manner. The IC CA analyzes the output voltage given to the non-inverting input with respect to a reference voltage at the inverting input.Copyright of this circuit belongs to smart kit electronics. In this page we will use this circuit to discuss for improvements and we will introduce some changes based on original schematic.

This is a high quality power supply with a continuously variable stabilised output adjustable at any value between 0 and 30VDC. The circuit also incorporates an electronic output current limiter that effectively controls the output current from a few milliamperes 2 mA to the maximum output of three amperes that the circuit can deliver. This feature makes this power supply indispensable in the experimenters laboratory as it is possible to limit the current to the typical maximum that a circuit under test may require, and power it up then, without any fear that it may be damaged if something goes wrong.

There is also a visual indication that the current limiter is in operation so that you can see at a glance that your circuit is exceeding or not its preset limits.

The AC voltage of the transformers secondary winding is rectified by the bridge formed by the four diodes D1-D4. The DC voltage taken across the output of the bridge is smoothed by the filter formed by the reservoir capacitor C1 and the resistor R1. The circuit incorporates some unique features which make it quite different from other power supplies of its class. Instead of using a variable feedback arrangement to control the output voltage, our circuit uses a constant gain amplifier to provide the reference voltage necessary for its stable operation.

The reference voltage is generated at the output of U1. The circuit operates as follows: The diode D8 is a 5. The voltage in the output of U1 gradually increases till the diode D8 is turned on. When this happens the circuit stabilises and the Zener reference voltage 5. The current which flows through the non inverting input of the op-amp is negligible, therefore the same current flows through R5 and R6, and as the two resistors have the same value the voltage across the two of them in series will be exactly twice the voltage across each one.

Thus the voltage present at the output of the op-amp pin 6 of U1 is The trimmer RV1 and the resistor R10 are used for the adjustment of the output voltages limits so that it can be reduced to 0 V, despite any value tolerances of the other components in the circuit.

Another very important feature of the circuit, is the possibility to preset the maximum output current which can be drawn from the p. To make this possible the circuit detects the voltage drop across a resistor R7 which is connected in series with the load. The IC responsible for this function of the circuit is U3. The inverting input of U3 is biased at 0 V via R At the same time the non inverting input of the same IC can be adjusted to any voltage by means of P2.

Let us assume that for a given output of several volts, P2 is set so that the input of the IC is kept at 1 V. If the load is increased the output voltage will be kept constant by the voltage amplifier section of the circuit and the presence of R7 in series with the output will have a negligible effect because of its low value and because of its location outside the feedback loop of the voltage control circuit.

While the load is kept constant and the output voltage is not changed the circuit is stable. If the load is increased so that the voltage drop across R7 is greater than 1 V, IC3 is forced into action and the circuit is shifted into the constant current mode. The output of U3 is coupled to the non inverting input of U2 by D9.

U2 is responsible for the voltage control and as U3 is coupled to its input the latter can effectively override its function. What happens is that the voltage across R7 is monitored and is not allowed to increase above the preset value 1 V in our example by reducing the output voltage of the circuit. This is in effect a means of maintaining the output current constant and is so accurate that it is possible to preset the current limit to as low as 2 mA.A power supply is a basic and essential requirement for electronics and electrical equipment and circuits.

There are various types of circuits and equipment, therefore, their demand of power supply is different for different electronics circuits. For instance, Wi-Fi modules, relays, motors, etc require different voltages. The simple solution for this is using batteries. Batteries are generally used to power up the Electronic Circuit and Projects, as they are easily available and can be connected easily.

But they drained off quickly and then we need new batteries, also these batteries cannot provide high current to drive a powerful motor. So the batteries discharges and also they make the circuit bulky.

Also batteries gets hot when the electronics is used for longer or excessively used and with time the life of batteries decreases. To overcome this problem we introduce a better and efficient solution which can be used in any circuit. Using this project you will be able to get variable power supply according to your electronic equipment without worrying about charging, discharging, heating issues etc. There are many methods available to generate the variable power supply but this is the easiest way as it requires cheap and easily available components.

Before getting into this projects let us know few things about the project. Arduino UNO is an open source platform which is used to develop electronics project.

It can be easily programmed, erased and reprogrammed at any instant of the time. In this project we are going to use Arduino UNO to control home appliances automatically.

How to Use LM317 for Making a Variable Power Supply Circuit

ATmega comes with pre-programmed on board boot loader which makes it easier to upload the code without the help of the external hardware. It has vast application in making electronics projects or products. Arduino IDE makes it much easier to program. It separates the code in two parts i. The function void setup runs only one time and used for mainly initiating some process whereas void loop consists the part of the code which should be executed continuously. This model consists of 6 analog input pins and 14 digital GPIO pins which can be used as input output 6 of which provides PWM output and analog using pinModedigitalWritedigitalRead and analogRead functions.

The board can be powered either from using USB cable which operates at 5 volts or by DC jack which operates between 7 to 20 volts. There is on board voltage regulator to generate 3. Arduino UNO has on board 6 ADC channels which can be used to sense or read analog signals ranging from 0 volt to 5 volts.

Therefore ADC helps to convert sensor values to analog values and feeds it into the microcontroller. There are many applications of ADC like temperature sensing, distance measurement, speed measurement and many sensors which generate analog values.

This is called as resolution which indicates the number of discrete values it can produce over the range of analog values. Since the ADC maximum voltage is 5 volts therefore each step of the ADC ranging from 0 to has value is equivalent to 5 mV approximately. Arduino IDE provides inbuilt function to read analog values: analogRead pin. By simply giving the pin number from A0 to A5 to which devices are connected this function helps us to read the analog values.

Pulse Width Modulation PWM is a technique used to generate the analog signals using some digital source by varying the width of the pulse while keeping the frequency constant.

The two main important things which define PWM are: duty cycle and frequency. Duty Cycle of a Signal:. The fraction during which a signal is ON in a complete period is called as Duty Cycle. For instance it can be used to control the intensity of light or speed of some motor. After a call of the analogWrite function, the pin will generate a steady square wave of the specified duty cycle until the next call to analogWrite or a call to digitalRead or digitalWrite on the same pin.

Frequency of a signal signifies how fast a signal completes its cycle means in how much time it switches from its ON state to its OFF state or vice versa.

By doing so at a particular duty cycle the output behaves like a constant analog voltage. The frequency of the PWM signal on most pins is approximately Hz.In this tutorial we will develop a 5V variable voltage source from Arduino Uno. Some digital electronic modules like accelerometer work on voltage 3.

Some even work on lower voltages. With this we cannot get a regulator for every one of them. So here we will make a simple circuit which will provide a voltage output from volts at a resolution of 0. So with this we may provide voltages accurately for the other modules. This circuit can provide currents up to mA, so we can use this power unit for most of the sensor modules without any trouble.

With the display in place we can easily see the power fluctuations in the system. This variable power supply unit contains button interface for the voltage programming. The working and circuit is explained below.

0-30 Vdc Stabilized Power Supply with Current Control 0.002-3 A

The voltage across output is not completely linear; it will be a noisy one. The two buttons here are for voltage increment and decrement.

variable power supply circuit

This value on display represents the variable voltage value. In those any one or all of them can be used as inputs for analog voltage.

This means that it will map input voltages between 0 and 5 volts into integer values between 0 and This means we can give a maximum input voltage of 5V for ADC conversion at any input channel. Since some sensors provide voltages from This resolution change can come in handy for some cases. For now we leave it as. We are going to use PIN3 for our purpose.Have you ever tried to design a variable regulated power supply? This article describes you how to design a variable power supply circuit.

Till now we have seen a lot of power supply circuits, but the main advantage of this power supply circuit is that it can vary the output voltage and output current. For smaller voltages, we normally use batteries as a reliable source. Instead of using batteries, which have a limited lifetime, a variable DC power supply can be used which is implemented in this project.

It is a robust, reliable and easy to use variable DC power supply. The working of the circuit is as follows. A transformer is used to step down the AC supply to 24V at 2A. A bridge rectifier is used to convert this voltage to DC. Depending on the settings of the POT, the ADJ pin of LM receives a small portion of the output voltage as feedback and the output voltage is varied.

With the help of this variable DC power supply, the output voltage can be varied from 1. This circuit can be used as a reliable DC source and acts as a replacement for batteries. It is important to attach the voltage regulator IC LM to a heat sink as it tends to get hotter during operation.

The above circuit uses only 15 v transformer at the input, so it can be varied maximum up to 15V. In order to increase the up to 30v input of 30v should be applied. Although the voltage regulator LM protects the circuit from overheating and overload the Fuses F1 and F2 are used to protect the power supply circuit. The rectified voltage at capacitor C1 is around So we need to use all the capacitors which are rated at 50v in the circuit.

Pot RV1 allows us to vary the output voltage between 0 to 28V. The minimum output voltage of the LM voltage regulator 1. In order to get 0V at the output, we are using 3 diodes D7, D8, and D9. Here 2N transistors are used to get more current.

Pot RV2 is used to set the maximum current available at the output. LM is the 3 pin series adjustable voltage regulator. This regulator provides output voltage ranging from 1.

This IC is easy to use and requires only two resistors to provide the variable supply. It provides internal current limiting, thermal shut down and it provides more line and load regulation as compared to fixed voltage regulators. Because of all these features, this IC is mostly used in a variety of applications. This circuit is studied theoretically and may require some changes to implement it in practice.

The fixed voltage regulator is used to offer fixed voltage at the output terminal and does not depend upon the input voltage supplied. Here is the circuit producing variable voltage Power supply designed using fixed voltage regulators. Imagine that the resistor which is attached between the com terminal and the output terminal of the regulator has a value of ohm R1. This implies that the value of current is


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