CT Sensor circuit not working

Hi everybody,

I recently built this project:

http://openenergymonitor.org/emon/node/58

At first it worked fine. After building the circuit I wrapped the CT sensor around a wire connected to a lamp (only one of the two wires of AC). When i switched on the lamp, the values shown in serial monitor changed proportionally. Wonderful, it worked OK.

Next day, i tested it again and nothing happened. I spent several hours checking the circuit and changing some of the components (and then changing every component, including Arduino itself) But i couldn't make it work again. The serial monitor shows a lot of readings from analog input, but when i switched on the light nothing happened...

I tested the CT sensor with a multimeter. It responds OK. It shows continuity and some measure in the multimeter display.
I don't have another CT sensor to try with, but it seems to me very weird that it could broke.

One strange thing is: sometimes when the light is switched on, the arduino hangs and i have to disconnect it from serial port and connect it again. I thought the arduino was the problem so i tried with one, two and three different boards... with no luck.

I don't supply code or schematics here because they are identically to the ones in the url above.

Any ideas about what can be happening?

Thank you in advance,

Carlos.

 

 

Robert Wall's picture

Re: CT Sensor circuit not working

You have made the circuit with only the current sensing part, the three resistors, capacitor and links on the left-hand side of the prototype board. Is that correct?

1. Is you Arduino working correctly without the prototype board connected?

2. If you connect the prototype board using ONLY the red and black wires, is the 5 V supply present and correct?  Do you measure 2.5 V d.c. approx. on both wires to the current transformer, and on the disconnected yellow wire?

3. If you now connect the yellow wire to Analog In 1, but do not put the c.t. around the lamp wire, does the Arduino hang when you switch the lamp on and off?

4. If you change this part of the sketch like this:

void loop()
{
  // emon1.calcVI(20,2000);         // Calculate all. No.of wavelengths, time-out
  // emon1.serialprint();           // Print out all variables
  Serial.println(analogRead(2));
  delay(1000);

}

do you see a number close to 512 printed every 1 second?

5. If you load the sketch from here http://openenergymonitor.org/emon/node/1705#comment-8535 do you see a flat line in the middle of the range, and when you put your c.t. on the lamp cable, do you see a full sine wave something like the picture/text file listing in that post?

 

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