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Proximity Sensing Module BM32S2021-1

US$ 3.15
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Product ID
Proximity Sensing Module BM32S2021-1


The BM32S2021-1 is an infrared proximity sensing module, which is designed for object detection applications. When an object enters the detection range, the reflected energy of the infrared will change. Proximity is determined by detecting changes in reflection. The product integrates active infrared emission, reception, and optical mechanisms. It features low power consumption, small size, long sensing distance (up to 100cm), and automatic learning of sensing distance.

The BM32S2021-1 can work in 2 modes. In I/O mode, when an object is detected, the LED on the module will light up, and the output pin will change from high to low. The default detection distance is set to 80cm in the factory, users can easily change the sensing distance. In UART mode, the external MCU can read and write various parameters through the UART interface, and quickly adjust module characteristics. In general usage cases, the I/O mode is sufficient.

For more product details, please refer to the BM32S2021-1 datasheet.

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Proximity Sensing Module BM32S2021-1


  1. Operating voltage: 3.0V – 5.5V
  2. Operating current: 1.5mA typical (3.3V/object detected at 85cm/scanning time = 0.5s)
  3. Standby current: 14µA typical (3.3V/default at 85cm/scanning time = 0.5s)
  4. Detection distance: 1 - 100cm (at 25°C, indoor, reflector is A4 paper), default 85cm
  5. I/O mode: Output pin is normal high, active low (when an object is detected), configurable
  6. UART mode:
    Send any command to module within 0.5s after power-on to enter the UART mode
    Minimum continuous reading time = 10ms
  7. Factory-calibrated

Arduino Demo Code

The demo code reads the proximity sensing trigger threshold value and displays on the serial monitor. Since the BM32S2021-1 can only enter UART mode at the condition of receiving a command after powered up, please upload the code to the board first and then connect the 4 wires of the module to the Arduino board at the same time.

Wire connection:

  1. Module pin 1 (VDD) connects to Arduino UNO pin 5V
  2. Module pin 2 (GND) connects to Arduino UNO pin GND
  3. Module pin 3 (TX) connects to Arduino UNO pin 2
  4. Module pin 4 (RX) connects to Arduino UNO pin 3

The result shown on the serial monitor is

Product Information

  1. Body size: 17.5 x 10.1 x 7.1 (mm)
  2. Weight: 0.8 g
  3. Packing List: BM32S2021-1 Proximity Sensing Module x 1


Module: Holtek BM32S2021-1, Proximity Sensing Module

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