SCT-013 Summary

Searching across Internet for SCT013 usage in ESPHome I’ve found plenty of examples.
Some of them better other worse.
Using SCT manufacturer docs[and other], which are mostly focused on Arduino I’ve calculated values and created schematic examples for different approaches.

For SCT013-000 100A/50mA we need to add a 22R burden resistor.
It comes from calculations:

  1. 100A * √2 = 141.4A
  2. 141.4A / 2000 turns = 0,0707A
  3. (3,3V / 2) / 0.0707A = 23,338048091Ω
    I’ve seen on Mouser available 23.2Ω resistor but closest easy available will be 22Ω.

From the Ohm’s law we have [V = I x R]:
0,050A * 22Ω = +/-1,10V AC RMS
1,1V RMS = ~ +/-1,56V Peak Voltage []
Since we have a DC biased 1,65V DC input we have ADC ranges:
1,65V + 1,56V = 3,21V max
1,65V - 1,56V = 0,09V min
It’s all in range of ADC.

Visual simulation here: