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Sonoff Dual R3 v2

An Arduino program for obtaining data from a Sonoff Dual R3 v2 with a bl0939 chip inside.

⚠️️Special Attention ⚠️️

Do not connect AC power and the serial connection at the same time The GND connection of the Dual R3 is connected to the live AC wire. Connecting serial with your PC will fry your PC and will electrocute you. Safety and fire danger.

DO NOT CONNECT ANY SENSORS TO THESE DEVICES!!! The GPIOs on the Dual R3 are connected to AC power!

Features

  • Initializes the bl0939
  • requests data
  • reads the data
  • does a CRC check
  • decodes the data string
  • converts the data to real values
  • Telnet for monitoring

How to calculate Voltage, Current , Active Power

More information

  • BL0939 Notes_V1.1_cn.pdf
  • BL0939_V1.2_cn.pdf

Needed values

  • Vref=1.218V
  • R1=0.51kOhm
  • R2=5*390kOhm
  • RL=1mOhm
Value Calculation
Current(A) = I_RMS_RegVref/324004RL
= I_RMS_Reg / ((324004*RL)/Vref)
= I_RMS_Reg / ((324004*1)/1,218)
= I_RMS_Reg / 266013,14
Voltage(V) = V_RMS_RegVref(R2+R1)/79931R11000
= V_RMS_Reg / ((79931R11000)/(1,218*(R2+R1)))
= V_RMS_Reg / ((799310,511000)/(1,218*(5*390)+0,51))
= V_RMS_Reg / 17158,92
Power (W) = WATT_RegVref²(R2+R1)/4046RLR1*1000
= WATT_Reg / ((4046RLR11000)/(Vref²(R2+R1))
= WATT_Reg / ((404610,511000)/((1,2181,218)((5390)+0,51)
= WATT_Reg / 713,105
Engergy(kWh) = CF*((1638,4256Vref²*(R2+R1))/(36000004046RLR11000))
= CF*((1638,4256(1,2181,218)((5390)+0,51))/(360000040461R0,51*1000))
= CF * 0,0001633819620262585
TEMP (°C) = (170/448)*(TPS1/2-32)-45
= ((85TSP1-5440)/448)-45

One full measurement frame from bl0939

55 3a 12 0 f0 2f 0 0 0 0 8c 61 3c bb 3 0 fc 10 0 0 0 0 b6 0 0 0 0 0 e2 1 0 7d 2 0 df

Byte: 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
Data: 55 3a 12 0 f0 2f 0 0 0 0 8c 61 3c bb 3 0 fc 10 0 0 0 0 b6 0 0 0 0 0 e2 1 0 7d 2 0 df
Byte Data Function How to calculate
00 0x55 HEADER
01-03 0x3a 0x12 0x00 I_FAST_RMS[A]
04-06 0xf0 0x2f 0x00 I_RMS[A] 002ff0 --> 12272 --> /266013 --> 0,046A
07-09 0x00 0x00 0x00 I_RMS[B]
10-12 0x8c 0x61 0x3c V_RMS 3C618C --> 3957132 --> /17159 --> 231V
13-15 0xbb 0x03 0x00 I_FAST_RMS[B]
16-18 0xfc 0x10 0x00 WATT[A] 0010fc --> 4348 --> /713 --> 6,1W
19-21 0x00 0x00 0x00 WATT[B]
22-24 0xb6 0x00 0x00 CF_CNT[A] 0000b6 --> 182 --> *0.000163 --> 0,0296kWh
25-27 0x00 0x00 0x00 CF_CNT[B]
28-29 0xe2 0x01 TPS1[internal] 01e2 --> 482 --> ((85*482-5440)/448)-45 --> 34,31°C
30 0x00 Free
31-32 0x7d 0x02 TPS2[external]
33 0x00 Free
34 0xdf CHECKSUM

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