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Arduino Pins
08/07/2022 at 20:43 • 0 commentsThe ESP32 feather V2 pins that are used for the sensor monitoring:
A4 - ADC1 (sensor 0)
I37 - ADC1 (sensor 1)
A3 - a reference VCC for the two current transformers.
The code compares the A3 reference value with the values read on A4 and I37. The difference between the reference VCC and the read value is what the transformer is producing. The average of this difference over a few sample periods is used to decide if there is current flowing (or not). Typical off state has a difference of 0 to 1. On state is if the average is greater than 1 for a set of sample periods (the duration and number of samples was derived semi-empirically on the test bench setup).
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Component Values
08/07/2022 at 20:37 • 0 commentsReferring to the great guidance from openenergymonitor.org, and based upon parts I had, the following values are used for the resistors and capacitor.
R1=R2 = 470K Ohm (provides 1/2 divider for 3V VCC, lower quiescent power use)
R3=R4 = 22 Ohm (burden resistor for the current transformer)
C1 = 10 uF (allows AC current to bypass resistor)
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Reference and Parts
08/07/2022 at 19:43 • 0 commentsInspiration and guidance from
https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/introduction
https://learn.openenergymonitor.org/electricity-monitoring/ct-sensors/interface-with-arduino
https://learn.adafruit.com/adafruit-esp32-feather-v2Parts List
Adafruit:
Adafruit ESP32 Feather V2 - 8MB flash + 2MB PSRAM (#5400, 19.95)
Adafruit FeatherWing OLED - 128x64 (#4650, 14.95)
Stacking Headers for Feather (#2890, 1.25)Mouser:
qty 2 Seed Studio AC current sensor, YHDC SCT013-100 100A, 50mA (#10199029, 11.50)
qty 2 3.5mm phone jack panel mount, Switchcraft (#35PRM3, 2.14)
Translucent Blue Box, Hammond (#1591XXLTBU, 5.83)Other:
m2.5 nylon screw/nut (https://www.amazon.com/gp/product/B01N9Q8YLE)
parts box: perfboard, 1/2" conduit for electrical panel