Discrete Educational Analog to Digital Converter
Fall Semester 2005
Purpose: The purpose of this project is to give CPE 495 students group design experience in developing a simple digital hardware design that expands upon the attributes of other designs. Students are required to develop a hardware design that is cost effective and can be effectively implemented on a small PC board.
Mandate: You have been asked to develop a 4-bit analog to digital converter that is made out of discrete components that can be used in the engineering classroom to illustrate the basic concepts of Analog to digital conversion principles. It is desired that your digital to analog converter design incorporate primarily discrete analog elements, that have digital, TTL logic level, interfaces that can be driven by external hardware based or software controlled design elements that will be developed by the engineering students who could use your design in a laboratory setting.
Project Overview: In the first phase of this project you will be asked to develop a working prototype of your design that illustrates its functionality on a solderless breadboard environment, and to develop a two layered PC layout for this design using the ExpressPCB product. The best design will then be manufactured. In the second phase you will be asked to take the actual manufactured PC board, fully populate it with the parts, and develop and to verify the functionality of the design by using a reconfigurable hardware based approach and a microcontroller based approach.
The schematic of an example 3-bit Analog to Digital Converter is shown below:
As a group 1) Implement this design on the solderless breadboards in the lab so that it will detect voltages within the range of 0V to 5V. Verify this design works as an analog to digital converter using one or more of the switches and/or LEDs. Also use a voltmeter as a reference. Do some web research on analog to digital conversion circuitry. Write a one page report that surveys the basic types of analog to digital conversion methods that are in common use. Identify if possible what type of AtoD converter this design represents. Also identify what is meant by the term quantization error. What is the quantization error associated with this three bit AtoD design over the 0 to 5V range?
Task2
Expand this design to represent a four bit analog to digital converter using the minimal number of components at the minimal costs possible. (Reference a major IC distributor and use large volume prices when calculating costs). Verify that this design works correctly on the solderless breadboards in a similar manner to the three bit design. The design must be made to meet the following specifications.
Specifications:
1) It must be made out of discrete components
2) It is to have a digital interface which allows the low-level functionality to be driven by external logic that will be supplied by the user.
2) It must be realizable using a maximum of a three voltage power supply of 5V, 12V, -12V or less.
3) It must be capable of measuring a voltage in the range of 0V to 5V.
4) It must be accurate within 8% for all voltages measured
5) It must be able to interface using standard digital TTL logic Levels using a maximum of 8 digital inputs/outputs.
6) Must incorporate one or more 74HC4051N Digital IC as part of the design solution
7) All components must come from the approved list of components present in the lab
8) The design must be able to be implemented on one half of an ExpresssPCB "Standard Service" PC board.
1) Ability to be used as an Digital to Analog Converter as well as a AtoD converter
2) Ability to chain two or more boards to increase the bit resolution
3) Ability to use a single supply voltage power supply or a dual supply voltage power supply or a tri-level-supply voltage power supply of less than +-12V.
4) Minimum number of components present in the design.
Completed Design and Breadboard Implementation: End of Class September 13, 2005
ExpressPCB PC Board Layout for design: End of Class September 20, 2005.