High sensitivity, low power consumption of infrared proximity sensing programme (1)

High-performance analog and mixed signal IC manufacturers Silicon Laboratories of innovation (core Branch Laboratory Co., Ltd., hereinafter referred to as Silicon Labs) Special Si1102 launched and Si1120 is currently the industry's most sensitive infrared proximity sensor, distance detection and low power is particularly outstanding.

Silicon Labs company of infrared proximity sensor series

Si1102 and Si1120 infrared proximity sensor consists of an infrared LED drive, infrared photo-diodes, an ambient light sensor (only Si1120 has) and control logic IC, external LED transmit can according to user's need for flexible installation and configuration (Figure 1).

Figure 1: silicon Labs company of infrared proximity sensor series applications.

Figure 2: block diagram of internal Si1102.

Si1102 is an independent work of infrared proximity sensors, able to drive a single infrared LED.

Infra-red LED transmit after nearly reach the built-in objects reflection infrared photoelectric diode and signal amplification and signal processing, final adoption and a set of detection threshold value comparison output a corresponding logic level. If the measurement result is greater than the threshold value, the output from PRX mouth a low level. This level signal output can be used as other devices MCU driven or interrupt input, thereby achieving close detection.

For example, the monitor application, Si1102 infrared proximity sensor can be used by site easily turn off the monitor and other features to save power.

This power saving feature is especially suitable for appliances, safety equipment and portable electronic products, but also can be applied in some of the IR detectors.

Figure 3: schematic diagram of Si1102 applications.

And unlike Si1120 Si1102 work need a main MCU control, and adds an ambient light sensor.

The device can receive infrared, the ambient light signals are sampled, the final output of a pulse width modulated pulse signal to MCU, realization of different applications. Silicon Labs of MCU can provide PCA (programmable counter array), so you can more easily measured output pulse width. Pulse width and reflective light intensity measurements in direct proportion to the square of the distance, which is inversely proportional to each other to determine the distance of objects. Si1120 can support multiple LED drivers, users can easily configure multiple LED to increase detection range. In addition, the devices under the control of the MCU can implement more advanced features, such as mobile phone application may allow users to phone fingers before moving it to a file.

Figure 4: the internal block diagram Si1120.

Figure 5: Si1120 of schematic.

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