I am currently developing a sensor based on an Arduino Mega and several sct-013-005 CT coils. I have a rough and ready circuit setup that senses current change on lighting circuits using the above CT’s, Using the Emonlib (credit to the author of that masterpiece) which works well. In the future I would like to monitor the correct current not just an on or off.
Now I have looked around the internet and understood some stuff and other stuff just went straight over my head about calibration etc.
My question is has anyone used this version, what calibration figure did you use and what values of resistor in the voltage divider circuit did you use?
When I get home I can post details of the figures I experimented with but I dont have them to hand at work (shhh dont tell the boss).
As long as the two resistors (R1 & R2 in the circuit here) are equal, then any value in range listed will be OK. The higher values are best used when you are powering with batteries, as they waste less current. If your Arduino is mains powered, then anything in the 10 kΩ - 56 kΩ area will be fine. Those resistors don’t affect the calibration.
The calibration constant is the value of current that gives you 1 V at the ADC input of your Arduino.
You have a voltage output current transformer, so your calibration constant is 5.
But note, you must not have the 33Ω burden resistor that’s shown on that diagram, because there is already a burden inside the c.t’s housing.
Nah, hes more into engines and motorbikes than circuits and code!
Thanks for the info, it looks like my rough and ready version wasnt so rough. I have 10k resistors and assumed the burden wouldnt be required for that CT. Phew is been a long time since I did basics but still remember something. Its just my calibration bit I didnt understand and had at 50.
