Cold Weather Package

1
Cold Weather Package

• Wei Liu
• Doddy Widjajakusuma
• ECE 445

2
Motivation

• Frost, Snow on car windshield
• From overnight weather
• From parking outside during work

3
Motivation
4
Overview

• Introduction
• Objective
• Design
• Testing
• Success/Challenges
• Recommendations
• Future Work

5
Introduction

• Device to prevent ice, snow formation on
  windshields
• For use with overnight parking
• For use with outdoor parking in wintertime

6
Objective

• Active sensor monitoring system
• Temperature
• Humidity
• PIC controlled
• Runs off lead-acid car battery
• Battery consumption monitor
• Heat element adaptable
• SIMPLICITY

7
Design

• Features
• Linear voltage output sensors
• Programmable conditions (PIC)
• PIC controlled relay switch

8
Design

• Temperature Sensor (LM235)
• Zener Diode model
• Linear operation
• 400µA - 5mA
• Simple Low cost

9
Design

• Humidity Sensor
• HIH-4000
• Linear output vs. RH
• High accuracy
• 200 µA draw

10
Design

• Power Source
• Car Battery (simulated)
• 5V regulated

11
Design

• PIC Control
• Programmable Conditions/ HEX code
• A/D conversion of sensors
• Output LED to signal device on/off

12
Design
13
Design

• PIC16F877A
• HEX code control of A/D
• 4.88mV per code from 0 5V
• Voltage gt Decimal gt HEX code
• Ex.
• 2.4V gt 492 gt 0x01EC

14
Design

• Heat Element Relay Switch
• T77S1D10-05
• 10A 120VAC/30VDC rating
• Can be used for battery or wall socket sources

15
Design

• Relay Switch
• PIC output too small for relay to register
• Transistor needed to boost output signal
• NPN transistor used

16
Design

• Battery Monitor
• LM3914 Dot/Bar Driver
• Simple analog circuit
• Adaptable from small to high voltage values
• Simple LED readout

17
Design

• Battery Monitor

18
Testing

• Temperature Sensor
• Tested linear output
• 2.4 V_at_ 25 C
• 2.1 V_at_ 0 C

19
Testing

• Temperature Output Curve

20
Testing

• Humidity sensor
• Tested linear output
• 1.59V _at_ 36RH
• 3.2V _at_ 80RH

21
Testing

• Humidity Output Curve

22
Testing

• Environment Conditions
• Humidity gt 75 80 RH
• Temperature Below 0 C
• Frost Occurs

23
Testing

• Power Source
• Voltage Regulator
• Regulated 12V to 5V
• Operates at 4.9V Avg
• Sufficient for all devices

24
Testing

• Battery Monitor
• Green LED on _at_12.65V
• Red LED on _at_11.89V
• Potentiometer used to calibrate range

25
Testing
Battery Monitor Output
26
Testing

• Relay switch
• Used LED to test functionality
• Breadboard sufficient for functionality
• Needs to be separate for actual use

27
Heating Methods

• Nichrome wire
• Heating tapes
• Infrared heater

28
Nichrome Wire

• Energy Consumption
• 22 gauge (45 inches) 2.34 Ahr
• 26 gauge (49 inches) 0.93 Ahr

29
Heater Test

• A piece of glass 6 mm thick
• 6 x 6 dimension
• 22 gauge nichrome wire
• Power 28.08 W
• 5 mm distance

30
Heater Test

• Change of temperature 34.8 C
• Time 600 s

31
Device Lifetime

• Car battery 50 Ahr
• Max 10 discharge, 5 Ahr
• Expected device lifetime
• Main circuit 5 Ahr / 0.165 A 30 hrs
• Main circuit heater (22 gauge)
• 5 Ahr / 2.5 A 2 hrs
• Main circuit heater (26 gauge)
• 5 Ahr / 1.1 A 4.5 hrs

32
Other Heating Methods

• Heating Tapes
• Can be cut to length
• Uses 120/240 VAC (wall socket)
• Can reach temperature in excess of 200 oC
• Flexible

33
Other Heating Methods

• Infrared Heater
• Reflective back coated to make it unidirectional.
• Emission 200 W/inch
• Power Consumption 300 W for 6 strip
• Easy to install

34
Successes

• Proposed breadboard design works fine
• PIC programming logic works fine
• Humidity and temperature sensors accurate enough
  for PIC logic
• Heating element design sufficient for testing
  purposes

35
Challenges

• Designing a heater with low power consumption
• Powering up the heater
• Simulating cold and humid condition for testing

36
Recommendations

• Attach nichrome wire to car sunshield
• Epoxy
• Embedded
• Position temperature and humidity sensor as close
  as possible to car windshield
• Install larger capacity battery

37
Recommendations

• Install extra deep-cycle battery
• Can be discharge up to 80
• Optional package for luxury car

38
Future Work

• Use infrared heater
• Power from wall socket (garage)
• No power consumption issue
• Interfacing Battery Monitor circuit with PIC
• Special program code for specific conditions

39
Thank you

• Questions?
• Comments?

40
References

• www.batteryfaq.org
• www.oemheaters.com
• www.andersonthermal.com/T3.htm
• http//www.reconnsworld.com/power_lm3914battmon.ht
  ml
• www.national.com/pf/LM/LM3914.html
• http//www.arttec.net/Solar_Mower/4_Electrical/Bat
  tery20Charging.pdf