APSC 100Project #31: Home Weather Station

Group 31QBilly Smith

Jacob BlackGeorge McDonald

Keith Brown

Supervised ByDr. Geoff Lockwood

Project Manager Bob

November 2, 2002

APSC 100Project #31: Home Weather Station

Presentation Overview

1. What We Learned

2. Our Goal

3. Preliminary Design

4. Components

5. Progress Report

APSC 100Project #31: Home Weather Station

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

APSC 100Project #31: Home Weather Station

Our Goals

1. Learn to build and analyze simple electronic circuits.

2. Produce an inexpensive weather station suitable for home use, with the capability to measure readings in the ranges of:

1. -40oC to +40oC2. 0% to 100% humidity (±2%)

APSC 100Project #31: Home Weather Station

Preliminary Design

Our circuit will contain the following:

• LM555 Timer/Square Wave Clock

• AD7819 Analog-to-Digital Converter

• Temperature Transducer Circuit

• Humidity Transducer Circuit

APSC 100Project #31: Home Weather Station

Components of Circuit

1. LM555 Timer/Square Wave Clock

2. AD7819 Analog to Digital Converter

3. Temperature Transducer Circuit

4. Humidity Transducer Circuit

APSC 100Project #31: Home Weather Station

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

APSC 100Project #31: Home Weather Station

Component #2(Analog-to-Digital Converter)

An AD789 linked with theDM9368 common-cathodedisplay driver and a sevensegment display

Picture courtesy of National Semiconductor

-Convert analog signals from the transducers to binary codes

-Convert binary code into a digital display

APSC 100Project #31: Home Weather Station

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

APSC 100Project #31: Home Weather Station

Minimum Supply Voltage

Our given temperaturerange produces afluctuation in signal of ±1V. An amplifier maybe required to make this signal usable for ourpurposes.

Picture courtesy of National Semiconductor

APSC 100Project #31: Home Weather Station

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

APSC 100Project #31: Home Weather Station

Output Voltage

- Transducer outputs within target range of AD Converter

Picture courtesy of National Semiconductor

APSC 100Project #31: Home Weather Station

Final Progress Report

1. The clock and Analog/Digital Converter have been constructed and tested

2. Next we plan to implement the temperature and humidity transducers

3. Group cooperation is satisfactory and there are no team issues to report