Digital Power Supply

Republic of the Philippines Tarlac State University COLLEGE OF ENGINEERING Tarlac City

Research Work In

DATA COMMUNICATIONS Submitted by: DON OVID E. LADORES BS-ECE-4F Submitted to: ENGR. IDRIS JEFFREY MANGUERRA Instructor- COMP 423

April 2009

Digital Power Suppy (Microontroller Based Power Supply) I- Introduction All power supplies provide electrical energy to do work, but how the feat has been accomplished over the centuries has varied considerably. The first power supplier was the Leyden jar. Invented in 1745 by Pieter van Musschenbroek (1692–1761), in Leiden,, it could store sizeable electric charges created by electrostatic devices, such as Alessandro Volta's electrophorus. The charge could be drawn from the jar and put to work. In 1800, Volta created the first battery, the "Voltaic pile." This reliable source of power produced electricity by means of a chemical reaction. The first mechanical electrical generator was invented by Michael Faraday in 1831. Joseph Henry and Faraday had independently discovered that a moving magnetic field could create the flow of electricity in a conductor. Faraday used this process of electrical induction to create an alternating current power supply. Soon after, Hippolyte Pixii built a hand-driven generator that produced alternating current (AC), and added a commutator to convert the power into direct current (DC). In 1867, inventor Zénobe Gramme, using the principles established by Henry and Faraday, built an improved dynamo for producing AC, and two years later he improved the DC dynamo. The two methods of power production divided scientists, with factions led by Thomas Edison and Nikola Tesla. Edison's invention of the incandescent light bulb in 1879 had created a demand for electricity, so he established a DC-generated power supply company in New York City. Direct current power supplies had two main disadvantages: power production was limited by arcing from the brushes that drew electricity from the dynamo's rotor, and long-distance transmission was prevented by resistance in electrical wires carrying the current. In 1884 Edison's plant was supplying power to over 11,000 electric lights in 500 buildings, with another 60,000 buildings receiving power from individual generators Edison had supplied.

II- Content of Study Literature Power supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output load or group of loads is called a power supply unit or PSU. The term is most commonly applied to electrical energy supplies, less often to mechanical ones, and rarely to others. Conversion of one form of electrical power to another desired form and voltage. This typically involves converting 120 or 240 volt AC to a well-regulated lower voltage DC for electronic devices. Low voltage, low power DC power supply units are commonly integrated with the devices they supply, such as computers and household electronics. Programmable power supplies are those in which the output voltage can be varied remotely. One possible option is digital control by a computer interface. Variable properties include voltage, current, and frequency. This type of supply is composed of a processor, voltage/current programming circuits, current shunt, and voltage/current read-back circuits. Programmable power supplies can furnish DC, AC, or both types of output. The

AC output can be either single-phase or three-phase. Single-phase is generally used for low-voltage, while three-phase is more common for high-voltage power supplies. When choosing a programmable power supply, several specifications should be considered. For AC supplies, output voltage, voltage accuracy, output frequency, and output current are important attributes. For DC supplies, output voltage, voltage accuracy, current, and power are important characteristics. Many special features are also available, including computer interface, over-current protection, over-voltage protection, short circuit protection, and temperature compensation. Programmable power supplies also come in a variety of forms. Some of those are modular, board-mounted, wall-mounted, and floormounted or bench top. Programmable power supplies are now used in many applications. Some examples include automated equipment testing, crystal growth monitoring, and differential thermal analysis III- Outcome A very important device for hobby electronic is a reliable DC power supply. Using a clever microcontroller based design, a power supply can be built which has more features and is a lot cheaper. Digital signal processors may soon become standard chips in ac/dc switchers and the like, to provide the kind of sophisticated control system originally envisioned for the "digital power supply." The microcontroller based power SUPPLY is developed with a view to make a flexible and an intelligent power supply controlled by a microcontroller of 8051 family and to eliminate the drawbacks or limitations of the existing systems. They are discussed. Most of the existing systems are hardwired and expensive, which increases the production and procurement cost. The PCBs are larger and complex because of low component integration. Due to hardwired logic the flexibility is low and a particular PCB circumvents to the specified requirements only. There is no room for change, as any modification in specification requires redesigning. The system parameters such as battery charging voltage, current are not programmable. They do not have the ability to generate logs or have periodic automatic self-testing techniques. User interface is not that interactive or informative. Description: The design of the microcontroller based power supply circuit satisfies the following requirements: • Read the voltages at 8 given points. • Indicate the battery or mains related errors on LCD or LED's and operate relevant relays. • Display the following parameter values--Error messages, Battery voltage, Battery charging current, Output voltage, Load current, Battery temperature, System temperature, Current time and date. • Logging of upto 250 errors along with time and date of its occurrence in nonvolatile EEPROM. • Editor to update certain parameters to enable the user meet his custom requirements. These are--Temperature at which to switch on the fan, Maximum Load Current and Maximum Battery Charging Current. • Automatic testing of battery every 12 hrs.

References http://findarticles.com/p/articles/mi_m0VVT/is_8_2/ai_n24997972/ http://www.bookrags.com/research/power-supply-woi/ http://en.wikipedia.org/wiki/Power_supply http://www.eetimes.com/op/showArticle.jhtml?articleID=18307859 http://www.linuxfocus.org/English/June2005/article379.shtml