Design and Construction of a 0-24V Variable Regulated Power Supply
CHAPTER ONE
AIM OF THE PROJECT
The aim of any power supply is to provide the required power to the load using an AC supply at the input. But for variable regulated power supply of 0 – 24v is to design a power supply with one output terminal with variable output voltage, and the output is gotten by turning the voltage adjuster known as the potentiometer (Martin Kaffei, 2011).
CHAPTER TWO
LITERATURE REVIEW
REVIEW OF VARIABLE POWER SUPPLY
Variable power supply is an electronic circuit that is designed to provide a variable dc voltage value across load terminals when the adjuster is turn.
The power supply output is given as input to the voltage regulating device that provides the final output. The voltage output of the power supply remains constant irrespective of large variations in the input AC voltage or output load current (Torres Gabriel, 2008).
The variable power supply circuit using a variable regulator as a regulating device. The input AC voltage (230 Voltas Vrms), is supplied to a transformer. The output will be a stepped down ac output appropriate for the desired dc output. This ac voltage is then given to a bridge rectifier to produce a full-wave rectified output. This is then given to a pi-filter circuit to produce a dc voltage. The filter output may have some ac voltage variations and ripples. This is further filtered using a regulating circuit whose output will be a variable dc voltage. This variable dc voltage is then given to a voltage divider, which supplies the different dc voltages that may be needed for different electronic circuits (Torres Gabriel, 2008).
REVIEW OF GENERAL APPLICATION OF POWER SUPPLY APPLICATIONS
Computer power supply
A modern computer power supply is a switch-mode power supply that converts AC power from the mains supply, to several DC voltages. Switch-mode supplies replaced linear supplies due to cost, weight, and size improvement. The diverse collection of output voltages also have widely varying current draw requirements (Nathan Kirsch (2005).
Welding power supply
Arc welding uses electricity to melt the surfaces of the metals in order to join them together through coalescence. The electricity is provided by a welding power supply, and can either be AC or DC. Arc welding typically requires high currents typically between 100 and 350 amperes. Some types of welding can use as few as 10 amperes, while some applications of spot welding employ currents as high as 60,000 amperes for an extremely short time. Older welding power supplies consisted of transformers or engines driving generators. More recent supplies use semiconductors and microprocessors reducing their size and weight (Oklahoma Wolf, 2007).
AC adapter
A power supply that is built into an AC mains power plug is known as a “plug pack” or “plug-in adapter”, or by slang terms such as “wall wart”. They are even more diverse than their names; often with either the same kind of DC plug offering different voltage or polarity, or a different plug offering the same voltage. “Universal” adapters attempt to replace missing or damaged ones, using multiple plugs and selectors for different voltages and polarities. Replacement power supplies must match the voltage of, and supply at least as much current as, the original power supply (Oklahoma Wolf, 2007).
The least expensive AC units consist only of a small transformer, while DC adapters include a few additional diodes. Whether or not a load is connected to the power adapter, the transformer has a magnetic field continuously present and normally cannot be completely turned off unless unplugged.
Because they consume standby power, they are sometimes known as “electricity vampires” and may be plugged into a power strip to allow turning them off.
In contrast, switched-mode power supplies can cut off leaky electrolyte-capacitors, use powerless MOSFETs, and reduce their working frequency to get a gulp of energy once in a while to power, for example, a clock, which would otherwise need a battery (Oklahoma Wolf, 2007).
CHAPTER THREE
CONSTRUCTION METHODOLOGY
BLOCK DIAGRAM
Before carrying out any project, the block diagram must be drawn and fully understood. Block diagram gives a pictorial understanding of any work. The block diagram of the system is as below:
CHAPTER FOUR
RESULT ANALYSIS
CONSTRUCTION PROCEDURE AND TESTING ANALYSIS
In building this project, the following procedures were properly considered,
- Purposing of the entire materials / Components needed
- Resistance check of the components bought with the help of ohmmeter before making the necessary connection with the components
- Drafting out a schematic diagram or how to arrange the materials/components.
- Testing the completed system to see if the design works and
- Finally, implementation of design of the project.
Having procured all the materials, I processed into the arrangement of the components into the Vero board, proper soldering of the components then followed. The components were all soldered into the board after which it was correctly confirmed done.
CHAPTER FIVE
CONCLUSION
At the end of this work a Variable regulated power supply was designed, this device was tested and was seen providing a variable voltages dc voltage of predetermined value (from 0 to 24v) across load terminals irrespective of ac mains fluctuations or load variations.
The power supply output is given as input to the voltage varying (lm 317) device that provides the final output. The voltage output of the power supply remains constant irrespective of large variations in the input AC voltage or output load current.
All power supplies have a power input, which receives energy from the energy source, and a power output that delivers energy to the load. In most power supplies the power input and output consist of electrical connectors or hardwired circuit connections, though some power supplies employ wireless energy transfer in lieu of galvanic connections for the power input or output. Some power supplies have other types of inputs and outputs as well, for functions such as external monitoring and control.
RECOMMENDATION
This project is designed to be used in electronics gadget where the need for diverse of dc supply for different electronics appliance. And should be used and maintain by a qualified personnel.
Working on this topic as my project is a good idea and it comes at the right time. I am suggesting that this particular topic should also be given to other students both in higher and lower class.
REFERENCES
- Quoting US patent #4937722, High efficiency direct coupled switched mode power supply: The power supply can also include crowbar circuit protecting it against damage by clamping the output to ground if it exceeds a particular voltage.http://www.patentstorm.us/patents/4937722-description.html
- Quoting US Patent #5402059: A problem can occur when loads on the output of a switching power supply become disconnected from the supply. When this occurs, the output current from the power supply becomes reduced (or eliminated if all loads become disconnected). If the output current becomes small enough, the output voltage of the power supply can reach the peak value of the secondary voltage of the transformer of the power supply. This occurs because with a very small output current, the inductor in the L-C low-pass filter does not drop much voltage (if any at all). The capacitor in the L-C low-pass filter therefore charges up to the peak voltage of the secondary of the transformer. This peak voltage is generally considerably higher than the average voltage of the secondary of the transformer. The higher voltage which occurs across the capacitor, and therefore also at the output of the power supply, can damage components within the power supply. The higher voltage can also damage any remaining electrical loads connected to the power supply.http://www.patentstorm.us/patents/5402059-description.html
- Malmstadt, Enke and Crouch, Electronics and Instrumentation for Scientists, The Benjamin/Cummings Publishing Company, Inc., 1981, ISBN 0-8053-6917-1, Chapter 3.
- Torres, Gabriel (2008-03-15). “How Much Power Can a Generic 500 W Power Supply Really Deliver?”. Hardwaresecrets.com. Retrieved 2009-03-28.
