Build Instructions

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• 1

  Specification

  
  

  item	content	remarks
  Power-supply voltage	5V	Assuming USB power supply
  controller voltage	5V, 3.3V
  consumption current	180mA (scan time 1.2mS)	Typical value for a single sensor board,
  power consumption	１W	Typical value for a single sensor board,
  Scan time board alone	1.2mS or more, 1 channel 150uS or more
  Scan time parallel continuation	800uS or more, 1 channel 100uS or more*
  Cost price	$67

  • In order not to reduce the detection distance, it is desirable to use 150uS or more per channel.
  • The measured distance of the sensor varies slightly depending on the microcontroller. Since the distance accuracy is poor, the distance cannot be determined by specifications. However, most microcontrollers can detect a distance of 8 inches.
• 2

  Hardware of the sensor

  Main board

  Main board pinout (JP1)

  pin number	PIN name	explanation
  1	+5V	Vcc 5V
  2	GND	GND
  3	A	Sensor channel 0bit
  4	B	Sensor channel 1bit
  5	C	Sensor channel 2bit
  6	SS	SPI Slave-Select (active-Low) Substrate selection when connecting in parallel.
  7	MOSI	SPI Input
  8	MISO	SPI Output (3.3V/5V switching JP2)
  9	SCLK	SPI Clock. Sometimes also "SCK" is used.
  10	SEL_SEN	Determine if SPI is for sensor or CLED High: Sensor (AD converter), Low: CLED
  11	OE_ILED	ILED Output Enable *ILED: Infrared LED  ILED enable/disable * The AD converter is read both when the ILED is on and when it is off.
  12	FIX_CLED	CLED Shift Register Latch *CLED: color LED Reflect the value of the shift register to the output
  13	OE_CLED	CLED Output Enable CLED output ON/OFF
  14	PWM_CLED	Adjust the brightness of the CLED with PWM (Pulse Wide Modulation) control Short to 13pin or 5V when not using PWM

  summary

  • SEL_SEN pin for SPI switching of sensor (AD converter) and CLED.
  • Set the ILED channel with ABC.
  • After CLED transfers data to the shift register, it is reflected in the output with a FIX_CLED pulse.
  • CLED ON can adjust the brightness with AND output of 13pin and 14pin and PWM of 14pin.

  Sensor sensitivity adjustment method

  ILED and PhTr You can adjust the sensitivity of the sensor by moving the black cover up and down, but please be careful as it may deviate from the optimum sensitivity.

  *ILED: Infrared LED,  PhTr: Phototransistor, CLED: color LED

  If the black cover is too high and cannot be lowered, cut the black cover as shown below.　Priority is in the order of A and B in the figure below.

  Precautions when sensing through transparent plates such as acrylic and transparent OLED

  • Close to the sensor or less than 0.4 inch away from the sensor. Otherwise, the sensitivity will drop significantly.
  • Before turning on the power, set the board so that it does not move. The sensor stores the surrounding brightness as a calibration value when the power is turned on. If the board is moved after the power is turned on, the calibration values will no longer match and accurate sensing will not be possible.
  • If you use acrylic, the sensitivity will be about 5% lower than without. With transparent OLED, the sensitivity is significantly reduced by about 1/7.

  Main board circuit diagram

  Sensor board circuit diagram

  SPI and ILED drive timing

  The infrared LED drive is triggered by SPI SS. Please note that this timing will vary slightly depending on the microcontroller and software library. The library has been confirmed to work on Raspberry Pi 3 and 4, Arduino Uno and Nano Every, and mbed Nucleo.
  

  SPI and ADC read timing

  The reading timing of the AD converter is near the center of the diagram. The on time of an infrared LED is 10 microseconds, but even when it is turned off, the output voltage of the phototransistor does not drop immediately. The sensor readings are therefore relatively stable.
  

  Note

  The sensor's infrared LED is fragile, so please do not touch it unless it is in danger of falling out or if it is unavoidable.

  Please turn off the power before inserting or removing the sensor. If you insert or remove it during operation, it may be damaged.

  If the sensor is operated directly under the air conditioner, the air conditioner remote control may not work due to the effects of infrared rays. In that case, you can avoid it by changing the location or angle.

• 3

  Software and interface of the sensor

  SPI interface setting (AD converter/shift register）

  • SPI-MODE:0
  • CLOCK：2MHz 
  • One cycle (time interval between accesses to the same ILED) is 1.2mS or more

  AD converter reading procedure
  

  1. OE_CLED：LOW
  2. A,B,C      ：Sensor channel setting
  3. SEL_SEN: HIGH Select sensor, do not select CLED

  
  4. OE_ILED：LOW ILED OFF  * ILED: Infrared LED
  5. SS          ：LOW
  6. SPI-read AD read value:vOff
  7. SS           ：HIGH

  
  8. OE_ILED：HIGH ILED ON
  9. SS           ：LOW
  10. SPI-read AD read value:from
  11. SS           ：HIGH
  12. Temporary sensor value:fromOn - fromOff Save in an array

  
  * The value obtained by subtracting the ambient brightness measured at startup from the temporary sensor value is the sensor value.

  Logic analyzer sensor reading diagram

  • Select the channel with A,B,C
  • Select the sensor by setting SEL_SEN to High
  • Turn on OE_ILED and emit infrared rays only during the second reading
  • Make the AD converter channel the same as A, B, and C channels.

  Read code of AD converter (Arduino C++)

  8 sensor readings

  void Sensor::setAd(bool bInit) {// bInit:add val to adAryInit[]
      for (int col = 0; col < COL_LEN; col++) {// COL_LEN：8
          setCol(col, bInit);    // *** sensing ***
      }
      if (!bInit)                // *** set CLED ***
          cled.set(val);        // sensor-data, indicator
  }

  Reading of a single sensor

  void Sensor::setCol(int col, bool bInit) {
      int ledSta = digitalRead(OE_CLED);
      digitalWrite(OE_CLED, LOW);
      out3bit(abc, col);
      digitalWrite(SEL_SEN, HIGH);
      digitalWrite(OE_ILED, LOW);   // ILED-OFF
      int vOff =getAdc(col);        // *** read ADC ***
      digitalWrite(OE_ILED, HIGH);  // ILED-ON
      int ofOn =getAdc(col);        // *** read ADC ***
      digitalWrite(SEL_SEN, LOW);
      digitalWrite(OE_ILED, LOW);   // ILED-OFF
      digitalWrite(OE_CLED, ledSta);
      if (bInit)
          adAryInit[col] += vOn - vOff - (vOff >> 2) + (vOn >> 4);
      else
          adAry[col] = noMinus(vOn - vOff - (vOff >> 2) + (vOn >> 4)- adAryInit[col]);
      val[col] = ad2val(adAry[col]);    // adAryInit[col]: Ambient brightness measured at startup
  }
  
  unsigned int Sensor::getAdc(int col) {
      digitalWrite(SS, LOW);
      SPI.transfer(6 | (col >> 2));
      unsigned char r1 = SPI.transfer(col << 6);
      unsigned char r2 = SPI.transfer(0);
      digitalWrite(SS, HIGH);
      return ((r1 & 0x0f) << 8) + r2;
  }

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