intelligent dew monitoring system for automobiles

IntelligentDew Monitoring Systemfor Automobiles

Table of Contents

1. Abstract - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

2. Introduction and Principles behind the Technology - - - - - - - - - - - - - - - - - - - - - - - - -

2.1. Definition of dew point

2.2. Reason for dew formation and remedy

2.3. Mode of measurement

3. Working - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 6

4. Benefits - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 7

5. Constraints - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 8

6. Conclusion - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 9

7. References - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 9

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The unique selling point of IDM is that it seeks to enhance consumer experience irrespective

of the car’s cost and variant. The statistics give an approximate figure of the number of cars sold in

2010 which includes hybrid and electric powered vehicles.

With this volume of passenger cars being sold, the problem of visibility impairment due to fog

accumulation becomes manifold. This in turn significantly increases the need for a device such as

the IDM, to help ensure passenger/driver safety.

Red indicates 10 - 15 million unit saleBlue indicates 6 - 8 million unit sale

2. Introduction

Figure 1: Passenger Vehicles Statistics


Intelligent Dew Monitoring System for Automobiles | 4

The humidity sensor and air temperature sensor are integrated on a single small size board. Dew

point is calculated based on the values obtained by the sensor. The sensor supports real time

information provision for quicker response through HVAC controls. The calibrated data is stored

in a non-erasable memory and embedded with a state-of-the-art microcontroller circuit that

controls cooling.

The entire unit is light weight since it is supported by the projection of rear view mirror. Glass

temperature is monitored using the temperature sensor on the windshield. When the glass

temperature reduces and becomes lower than the dew point temperature, dew is formed on

glass. Temperature compensation takes care of the temperature of passive elements in the

assembly.

Figure 2: Temperature - Humidity sensor

Dew point hygrometers with capacitive operation P14 or P14 thermo

Glass temperature thermistor sensorOmega / MEAS

Humidity reference temperature DHT22

Microcontroller - Arduino Board Active HVAC control

Returns air temperature value

Returns value to comparator and circuit

Calculates humid levels in RH value

Device Specification Function

Table 1: Devices used and their functions

3. Working



IDM assists in measurement of the windscreen temperature and timely prevention of fog on the windscreen.

There is no initiation required from driver’s end. Vehicles generally require the driver to manually control

HVAC controls to clear the glass of fog.

Glass temperature drops much before water droplets

begin forming. While driving, it is difficult to keep track

of the accurate time required for state change.

Regions specified by red, yellow and blue dots are not

feasible for installation. This is because the sensor

gets exposed to defrost and frost bleed that controls

dew formation when the AC gets switched on. Since

the sensor will obstruct the path of cool or hot air, the

drop or rise in temperature will negate the purpose of the IDM. As a result, the sensor will be slower in

responding the next time cabin temperature rises. Thus the system is installed at the junction of the

windshield and car roof or behind the rear view mirror (indicated by green). Very often the amount of air

circulated due to conditioning is insufficient to remove the humidity if there are more people in a car.

Optimum regulation of ventilation for wind-screen is enabled by the air conditioning system with better

comfort in the interior. A common tendency while driving is to switch off the AC once the cabin has cooled to

a desirable temperature. The cycle of moisture retention continues and the driver chooses to alternate

between switching the system on and off.

It takes care of the psychological and physical implications arising due to reduced visibility. Psychological link includes irritation and restless to drive in better visibility.

Physical link includes use of arms and legs to strike a balance between driving and trying to reach out with a cloth to clean the glass and at the same time alternating the AC controls to preventdew formation.

IDM provides total driving comfort

The IDM system offers several advantages that makes it an attractive business proposition:

1. Reduced lead time:

2. Driving comfort:

4. Benefits



Efficient power consumption by the automatic air conditioning system. Keeping the AC on reduces

the temperature but involves energy use. The IDM sensors provide an optimized solution to control

the timing of the conditioning and switching it off when the humidity content drops below the limit.

The conditioning circuit must fulfill the following objectives:

Reduce or eliminate the recirculation of cabin air by introducing more outside air

Engage or increase the pumping capacity of the air conditioning compressor (greater dehumidification)

Increase air flow volume to the windshield. The defogging must be effective in all parts

Increase the temperature of the discharge air from the HVAC module so that there is no condensation on coil

Engage the rear window defogger

Response of the sensor elements

Installation space available

Quality of thermal contact with glass

The IDM ensures safe driving conditions under fog and cold conditions. In developing countries like India,

roads are poorly lit with no dividers. Moreover while driving on highways at night when it is pitch black, if dew

forms on glass and no attempt is made to clean it up properly, the light falling on glass undergoes reflection

and refraction. Sometimes it becomes difficult to analyze whether vehicle coming from opposite direction is

a car or a truck.

While the device takes care to ensure full functionality and total safety of the vehicle occupants, there are a

few constraints that manufacturers can take cognizance of and implement these in their R&D and

production stages to improve the overall accuracy of the sensor:

3. Energy saving:

4. Enhanced safety

5. Constraints



The Dew point monitor and HVAC actuation system is a sensor based technology that can prevent

accidents, reduce manual effort and introduce automation. The process of preempting fog

occurrence can be accomplished using accurate sensors. By incorporating such low cost measures

in low end as well as high end car models, consumer experience can be enhanced with the

provision of comfortable and safe driving environment.

1. Reliable, High Quality Infrared Sensors Have Found Their Way Into Automotive Climate

Control Roger Diels, Melexis NV, Business Unit Manager Climate Control

2. Vernier.com- Humidity Sensor

3. Choosing a Humidity Sensor: A Review of Three Technologies – Sensors. - www.sensorsmag.com

4. Condensation inside windshield on rainy days - RX8Club.com

5. Development and Application of an Integrated Dew Point and Glass Temperature Sensor-

Delphi Automotive System by: Thomas M. Urbank, Sean M. Kelly, Timothy O. King and Charles A. Archibald

Designed By: Mayuri Infomedia

This whitepaper is published by HCL Engineering and R&D Services.

The views and opinions in this article are for informational purposes only and should not be considered as a substitute for professional business advice. The use herein of any trademarks is not an assertion of ownership of such trademarks by HCL nor intended to imply any association between HCL and lawful owners of such trademarks.

For more information about HCL Engineering and R&D Services,Please visit http://www.hcltech.com/engineering-rd-services

Copyright@ HCL TechnologiesAll rights reserved.

7. References

Author InfoAditya Patnaik

6. Conclusion
