Weather Station

1
Weather Station
2
Weather Station Team

• Sarah Jackson
• Briggs Brantley
• David Moak
• Hal Fleming
• Dr. Robert Reese (Advisor)

3
The Problem

• Most weather data is collected at airports.
• This data is used to forecast regional weather.

4
Overview

• The constraints of the weather station design.
• Layout of the design.
• Using hardware to measure weather parameters.
• Implementing software solutions to the problem.

5
Practical Constraints
6
Technical Constraints
7
Design

• Block diagram

Sensors
Radio
Sensors
Radio
PACK
BASE
RS232
PC
8
Hardware

• Microchip PIC18F242
• 10-bit A/D converters
• Timers
• Interrupts
• Sleep
• USART
• Temperature limits -30 to 85 C

9
Hardware

• Rain Gauge
• Triggers at 0.1 inches
• Sends pulse
• Uses a magnetic reed switch

10
Hardware

• EEPROM
• Non-volatile memory
• 6144 bytes to store 24 hours of data
• 128 bytes per reading
• LCD
• 2 X 16 character matrix
• On-board controller
• Backlit display

11
Hardware

• Anemometer
• Wind cups
• Relative encoder
• Pulse train
• Wind Direction
• Wind vane
• 3-bit absolute encoder
• Measures 8 directions

12
Hardware

• Humidity Sensor
• Frequency output is proportional to the ppm water
  in the air.
• The frequency is proportional to Relative
  Humidity () if a 100ppm timer resistor is used
  at R1.
• Astable design using a TLC-555

13
Hardware

• Humidity Circuit

14
Humidity Sensor (PSPICE)

• Frequency output from simulations

• High Capacitance
• (high humidity)
• Low Capacitance
• (low humidity)

(RH calculation accurate to 0.1)
15
Hardware

• Temperature Sensor
• Thermistor
• Application based on Humidity Sensor Schematic
• R1 is Thermistor (Variable)
• C1 stays constant
• Removes temperature drifts present in multiple
  Op-Amp based designs
• No Self-Heating (very low current)
• Still need to characterize this circuit

16
Hardware

• Radio Transmitter
• Industry standard DIL form factor
• Easily change
• Manufacturers
• Operating frequency (315MHz to 2.4GHz)
• Low power consumption
• 4mA during transmission
• Operates on unlicensed frequencies
• 433.92MHz
• ITU and FCC approved for intermittent operation

DIL is Dual In-Line. ITU is International
Telecommunications Union.
17
Hardware

• Radio Receiver
• Industry standard SIL package
• Same features as Transmitter
• Plus integrated signal strength data
• Useful for debugging
• Possible feature

SIL is Single In-Line.
18
Power Budget
PACK will not operate all sensors at once.
19
PC Software

• Display of current and historical data
• Interface to Base via RS232
• Will hold 20 years of data in lt50MB of file space
  without compression
• Basic forecasting

Current Proposed PC-Software
20
Working together

• The layout of this product will offer hardware
  solutions that integrate with the power of the PC.

PC
Pack
433.92 MHz
Base
RS 232
21
Timeline
Hardware Pack 2/28/05 Base 3/12/05
Firmware Pack 2/28/05 Base 3/12/05
Software User Interface 3/1/05 Communications 4/22
/05
Hardware integrated with firmware 4/2/05 Software
ready for prototype 4/22/05 Prototype ready
for testing 4/23/05
Individual sensors are tested as built
22
Progress
Jan 13
Apr 23
Feb 23
Mar 23
Hardware
Firmware
Software
23
Difficulties

• Absolute encoder is difficult to obtain.
• Fault tolerance and number of sensors adds
  complexity to firmware.
• Data formats between private data collection
  networks are not standardized.

24
Conclusion

• Hardware and software are integrated to solve the
  problem.
• Sensors are NIST-traceable ensuring precision.
• Parallel implementation of designed components
  allows problems to surface early in the process.

25
Conclusion

• Questions?