Power Supply And Function Generator example essay topic

Lenora Vidaurrazaga& Christina Meyers CET 402 Senior Project Prof. KavianpourDeVry University Spring 2005 Project Proposal Due: April 8, 2005 Table of Contents: Executive Summary... 1 Introduction... 2 Project Operation... 7 Project Scheduling (Gann t Chart)... 11 Bill of Materials... 13 Future Use and Expansion...

14 Hardware Schematics... 15 Hardware and Software Block Diagrams... 18 Bibliography... 20 Executive Summary: Objective: The objective of our senior project is to develop portable lab equipment and software interface for first year college students. The idea of our project is to allow portability and convenience for students to perform basic electronic labs at home. It is meant as a learning tool to generate a comprehensive, hands-on guide for students to use on their own time, while still being cost effective.

Our project will utilize the 68 HC 12 Axiom board, custom built variable power supply and function generator, LCD, and keypad, interfaced with a PC using custom built oscilloscope software and a Graphical User Interface (GUI). Our project will employ a high level programming language using C++ for the development of the oscilloscope data, graphs, and mathematical operations. Our project will use Visual Basic to develop the GUI that will display information and allow a menu selection for the components being used, such as the waveform and frequency. It will also incorporate Assembly language to communicate between the 68 HC 12 and the PC. Block Diagram: Application: The project will first require a password using the keypad and displaying a confirmation on the LCD. It will then require the setting of the desired voltage on the power supply, which can be checked on the LCD.

The function generator will be responsible for generating the preferred waveform. The GUI will then display menu options to select graphing utilities used for the oscilloscope and then display the graph with the options selected. Future Expansion: This project could also include a multimeter and curve tracer. It could also be improved by having a higher voltage and a better regulated power supply. The function generator could also have higher bandwidth and frequency. Cost: Estimated total cost is $316.

Introduction: When we visualized our senior project, we decided that engineering and electronic students in college could make use of portable, inexpensive, simple equipment in order to demonstrate concepts off campus. This equipment would not necessarily have all of the functionality and versatility of the lab equipment, but it would be useful in demonstrating concepts. The current lab equipment is great for school, but if students have a need to use the equipment at home such as to finish labs, learn more, or just hobby use, they are left without an inexpensive alternative with the equipment currently on the market. Our solution was to address these issues with our project which we named "Lab In A Box". This would allow students to have a portable oscilloscope, power supply, and function generator at a greatly reduced cost. The labs performed at DeVry University usually only requires low bandwidth and low voltage equipment.

The power supplies in the labs are DC with the capability of +6 V and +/-25 V. The function generator is a 15 MHz waveform generator that is capable of sine, square, triangle, and saw-tooth waveforms. The oscilloscope is 100 MHz and has functions such as voltage, time, trace, setup, auto-scale, Voltage peak-to-peak, and so on. When researching the previous labs done for EET and CET students, we found that no more than 25 V is used at any given time in a lab. There were requirements though for a dual power supply as well as a function generator and oscilloscope. We also found that we mainly used the sine wave for the labs and that 6 KHz for the function generator would be sufficient. There are many oscilloscopes on the market.

There are both hardware to software oscilloscopes that range in price from $150 to $10,000. Considering the performance we are seeking, comparable prices would be from $150 to $725. There are many hardware manufacturers such as Hewlett Packard and Instek. The Hewlett Packard 54600 B is the model used in the DeVry labs which ranges from $1200 to $2550. There are a few software manufacturers as well. Some can be downloaded for free while more advanced programs can cost up to $725.

There are also many function generators on the market as well. There are a variety of software and hardware function generators in any range from $185 to $10,000. Some of the manufacturers include Hewlett Packard, Instek, and Tektronix. The Hewlett Packard 33120 A is the one used in the labs at DeVry. This has an average price of $1350. Also, another piece of lab equipment used is the DC power supply.

This is a hardware device used only for powering circuits and equipment. Some major manufacturers include Hewlett Packard, and Instek. These range in the price to anywhere from $235 to $11,000. For the purposes and specifications of our requirements the range is from $235 to $1238.

The Hewlett Packard E 3631 A power supply used at school has an average price of $1238. The portability of this equipment is minimal. Almost all of this equipment is heavy, weighing anywhere between 5 to 15 pounds. The combination of the three makes it almost impossible to transport. The equipment is also out of the price range for most college students. Students would be looking at spending around $3788 for the kind of lab equipment used at DeVry.

By creating an inexpensive and portable oscilloscope, function generator, and power supply that fits in one box about the size of a brief case we " ve addressed the primary issues associated with this equipment. This project has many applications and many future expansions and functions that can be added on. By having a variable floating DC power supply, 7 Hz-6 KHz function generator, and oscilloscope with leads connecting to any circuit built, the comprehensive hands-on learning tool would be ideal for most DeVry students. Project Operation: There are three main parts to this project: the power supply, function generator, and oscilloscope. There are a few hardware and software requirements for these components. The power supply will require two wall wart power supplies connected to two potentiometers to control the variable voltage and display it on the LCD.

Then it will connect to the student's circuits. The function generator can be completed in two ways. One method is to assemble it through hardware. This would have little involvement with the 68 HC 12, but would allow a more hands on approach. The other technique is to generate it through software. This would allow it to be more portable, but creates more use of the computer instead of circuits.

The function generator then communicates with the oscilloscope to create the waveform. The oscilloscope then plots the desired waveform on the PC. The software will be user-friendly, and with the connections will allow a fully functioning lab system. Operating Specifications: These requirements are based on the function generator operating through software. o Motorola CML-912 Dp 256 development board with a Motorola MC 9 S 12 DP 256 2 5 k potentiometer so 2 15 V DC wall wart so 4 test lead so Lcd Keypad Motorola 68 HC 12 source code Visual Basic code C++ code Project Analysis: The three components can be built many different ways.

If the function generator is built through software using the sound card, the programming would be intense, but the result would create a better waveform generator. Since the oscilloscope interfaces directly with the function generator, making both of the components software would prove for a closer real time output. The following information and graphics were acquired from a website about software oscilloscopes and function generators. Typically, the 'MIC's ocket of a sound card has an input impedance of 1500 Ω ~ 20 kΩ (card dependent) and requires a minimum input signal level of at least 10 mV.

It only allows a single channel input. The 'Line In's ocket of a sound card has an input impedance typically around 10 kΩ ~ 47 kΩ (card dependent), and the input signal level of this connection is in the range of 500 mV ~ 2 V (card dependent). Generally, the 'Line In's would be used as the primary input connection for Oscilloscope and Spectrum Analyzer as it offers better Signal-to-Noise Ratio (SNR) and bandwidth. The 'Line Out' connection of a sound card has an output impedance typically in the range of 20 Ω ~ 500 Ω (card dependent) and can output signal up to 2 V typically (card dependent).

It has better SNR than the 'Speaker' connection. The 'Speaker' connection of a sound card has a typical output impedance of 8 Ω (card dependent) and output power of 2 W (card dependent). For input connection, the simplest way is to directly connect the signal under test to the sound card 'Line In' or 'MIC's ocket (see the figure below). However, this kind of connection requires the tester to be extremely careful to ensure the input signal is within the acceptable range before connecting. Otherwise the sound card or even the PC may get burnt.

The following figure shows the output connection for Signal Generator. The resister is used to prevent the possible short circuit of the output. It can be omitted if you are careful enough. As the output impedance of a sound card is very low, there should not be any impedance matching problem when connected to external circuit. The circuit under test needs to be floating (i.e. isolated from earth), which the power supply is. The power supply is fully rectified, induct ly coupled, and has a floating voltage.

Rather than create a power supply from scratch, we opted to use two 15 V wall warts capable of delivering 500 mA. The power supply is being used in conjunction with two potentiometers with the ability to vary the output voltage. The variable voltage power supply is capable of being used with many diverse circuit schematics relevant to numerous EET classes. It would be proved however by incorporation of a digital read out on the LCD of the current output voltage. Bill of Materials: The following is a list of materials used for this project: o 1 Motorola CML-912 Dp 256 development board with a Motorola MC 9 S 12 DP 256 microcontroller Motorola... $150.00 o 2 5 k potentiometers Radio Shack...

$6.00 o 1 Vector Board Fry's Electronics... $30.00 o 1 Keypad DeVry University... $50.00 o 1 LCD DeVry University... $50.00 o Wood and mounting hardware Home Depot... $30.00 o 2 15 V DC wall warts Radio Shack... $28.00 Total Cost...

$316.00 Future Use and Expansion: In the future, this project could also include a Multimeter and curve tracer. The power supply could have a ground port, as well as a fuse. In addition the Motorola board could be left out, and instead have programmable memory. Hardware Schematics: Inside the Wall Wart (Power Supply) Power Supply Schematic Example of dual power supply with voltage output of +15 V to +30 Example of circuit with two power supplies up to 15 V each Example of circuit with an op-amp of positive voltage and negative voltage with respect to ground Hardware built function generator Hardware and Software Block Diagrams: Flow Chart of Project

Bibliography

Arminian, Ali and Marian. "Electronic Devices". Pearson. 2004.
web Boyle stad, Robert. "Introductory Circuit Analysis. Prentice Hall. 2003.