Melexis has developed a new, automatic windshield wiper IC with an MLX75308 sensor, which automatically controls auto-windshield glass wipers when fog, mist, road spray or rain begin to hinder the transmission of light via the frontal windshield glass in vehicles.
The new rain sensor semiconductor chip is a single device application and it controls all the major components, which are located in a light and rain sensor module and is usually positioned at the back of the front windshield of a car or any other automobile. The sensing system comprises of photodiodes, near infrared LEDs, a microcontroller, a network bus interface IC and an MLX75308.
The MLX75308 has the ability to detect mist or raindrops even in the presence of strong sunlight. In the past to overcome this problem, expensive optical waveguides or very complex algorithms were used which would diminish responsivity and increase incidences of false wipes. The MLX75308 would separate and restrain the sun signal from the rain signal which would be measured by the photodiodes.
Automobile OEMs keep optimizing automatic wiper systems so that they would appeal to consumers. Certain manufacturers use a relaxed rate of wiping, while others fix wipers which would be activated at the slightest sign of rain. Some manufacturers like to activate the headlights when the wipers operate and other OEMs would prefer to consider the ambient light level input to decide if and when headlamps need to be switched on. If the signal data is sent to the ECU in a digital form through SPI, the MLX75308 would permit either the OEM or the system integrator to find out how the sensor data would influence the system level behavior.
With a flexible design, the MLX75308 copes with an extensive variety of windshield angles ranging from 40° to 90° along with different shading and tinting. Implementation of sensors require a wider sensing coverage area, more number of photodiodes and LEDs for enhancing rain detection threshold levels or sometimes lesser number to reduce size and cost. A wide current ranging from picoamps to milliamps needs to be covered by the system as light levels differ greatly on bright, sunny days and nights.
Melexis claims that the sensor could handle all the above options with the help of its analog signal control chain, which is programmable, along with a digital signal processing on chip.
Source: http://www.melexis.com/