How to Use an IR Sensor in Daylight

When using infrared (IR) sensors, one of the biggest challenges is dealing with sunlight, as it can interfere with the sensor's ability to detect its intended target accurately. This article explores various methods to mitigate the impact of sunlight and maintain the effectiveness of your IR sensor in daylight.

Overview of IR Sensors and Sunlight Interference

Traditional IR sensors detect the presence of infrared waves. These waves are part of the electromagnetic spectrum, just like visible light and other types of radiation. However, sunlight, which is rich in visible light, often interferes with the sensor, causing it to detect sunlight as if it were infrared light. This interference can lead to incorrect readings and errors in detecting the target.

Methods to Improve IR Sensor Performance in Daylight

Placing an IR Filter in Front of the Sensor

One effective method to combat sunlight interference is to place an IR filter in front of the sensor. Filtering out the visible light portion of the spectrum can significantly reduce the amount of sunlight the IR receiver encounters. This is a straightforward solution that can be implemented with minimal additional components.

Modulating the IR Transmitter

Modulating the IR transmitter data is another strategy to handle sunlight. By designing the IR signal to be an AC (alternating current) signal, you can make the sensor ignore the DC (direct current) component of the sunlight. This approach involves encoding the data in a way that allows the IR receiver to distinguish between the desired signal and the unwanted sunlight.

Light and Daylight Filtering in Modern IR Sensors

Recently, IR Led proximity sensors have been designed with integrated detection and cancellation of daytime interference. These sensors have built-in filters that can filter out the effect of sunlight while sensing the reflective surface. It's crucial to ensure that the sunlight does not fall on the surface to be sensed, as it can still cause interference.

Choosing the Right IR Sensor with Daylight Blocking Filters

There are modern IR sensors available that come with integrated daylight blocking filters. For example, the CNY70 is a typical example of such a sensor. The receiver of this sensor is often dark violet or blue, which is the result of a filter coating. For the most precise results, you might consider adding an optical filter that blocks light below 700nm, as sunlight is centered around 570nm.

Conclusion

Using an IR sensor in daylight requires careful consideration of the methods used to filter out unwanted sunlight. By understanding the principles of interference and employing appropriate filtering techniques, you can ensure that your IR sensor functions correctly even in bright conditions. Whether through simple IR filters, modulation techniques, or built-in daylight filtering, selecting the right approach can significantly improve the accuracy and reliability of your sensor.