This paper talks about a new sensor equipped mechanism for preempting fog formation in automobiles and clearing the fog by setting the system controls appropriately.

1. Intelligent
Dew Monitoring System
for Automobiles

2. 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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4. 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 sale
Blue indicates 6 - 8 million unit sale
2. Introduction
Figure 1: Passenger Vehicles Statistics
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Intelligent Dew Monitoring System for Automobiles | 4

6. 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 sensor
Omega / 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
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Intelligent Dew Monitoring System for Automobiles | 6

7. 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 prevent
dew 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
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Intelligent Dew Monitoring System for Automobiles | 7

8. 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
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Intelligent Dew Monitoring System for Automobiles | 8

9. 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.
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Please visit http://www.hcltech.com/engineering-rd-services
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7. References
Author Info
Aditya Patnaik
6. Conclusion
Intelligent Dew Monitoring System for Automobiles | 9