1. Group 31Q Billy Smith Jacob Black George McDonald Keith Brown
Supervised By
Dr. Geoff Lockwood
Project Manager Bob
November 2, 2002

2. Presentation Overview
What We Learned
Our Goal
Preliminary Design
Components
Progress Report

3. What We Learned Tutorial #1: - construction of circuits
- methods for measurement of voltage, current, and resistance
Tutorial #2: - operational amplifiers
Tutorial #3: - analog-to-digital converters
- seven-segment displays

4. Our Goals Learn to build and analyze simple electronic circuits.
Produce an inexpensive weather station suitable for home use, with the capability to measure readings in the ranges of:
-40oC to +40oC
0% to 100% humidity (±2%)

5. Preliminary Design Our circuit will contain the following:
LM555 Timer/Square Wave Clock
AD7819 Analog-to-Digital Converter
Temperature Transducer Circuit
Humidity Transducer Circuit

6. Components of Circuit 1. LM555 Timer/Square Wave Clock
2. AD7819 Analog to Digital Converter
3. Temperature Transducer Circuit
4. Humidity Transducer Circuit

7. (LM555 Timer/Square Wave Clock)
Component #1
(LM555 Timer/Square Wave Clock)
used to generate a square-root wave
sends an analog clock signal to the AD converter
square-root wave produces intervals of reading/sampling of the analog input signal
Pictures courtesy of National Semiconductor

8. (Analog-to-Digital Converter)
Component #2
(Analog-to-Digital Converter)
An AD789 linked with the
DM9368 common-cathode
display driver and a seven
segment display
Convert analog signals from the transducers to binary codes
Convert binary code into a digital display
Picture courtesy of National Semiconductor

9. (Temperature Transducer)
Component #3
(Temperature Transducer)
LM35 precision integrated-circuit temperature sensor
±0.5oC accuracy guaranteed (at +25oC)
Rated for –55oC to +150oC range
Picture courtesy of National Semiconductor

10. Minimum Supply Voltage
Our given temperature
range produces a
fluctuation in signal of
±1V. An amplifier may
be required to make this
signal usable for our
purposes.
Picture courtesy of National Semiconductor

11. (Humidity Transducer)
Component #4
(Humidity Transducer)
HIH-3605-A transducer circuit allows us to read the relative humidity
Send an analog signal to the AD (Analog/Digital Circuit) converter
Picture courtesy of National Semiconductor

12. Picture courtesy of National Semiconductor
Output Voltage
Transducer outputs within target range of AD Converter
Picture courtesy of National Semiconductor

13. Final Progress Report
The clock and Analog/Digital Converter have been constructed and tested
Next we plan to implement the temperature and humidity transducers
Group cooperation is satisfactory and there are no team issues to report