[TriEmbed] TriEmbed Digest, Vol 20, Issue 11

[Martin Brooke]

I have used these
<http://www.amazon.com/SCT-013-030-Split-core-Current-Transformer/dp/B005CTWE8A/ref=sr_1_2?ie=UTF8&qid=1421267065&sr=8-2&keywords=AC+Current+Sensor>
low
cost current transformers   There are more or less sensitive versions this
one is 30A, probably good for a water heater.
There are also open resistor versions that you can customize to get any
sensitivity you like.  (Or you can open it up and cut out the resistor
inside)

You need to separate the hot AC wire and run it through the transformer.
This does mean you will have to strip off the outer cover of the wire
and expose the Hot wire.

the ADC on arduino can capture a pretty good sine wave of the current flow
as follows:

#define Arraysize 300
#define loopdelay 1
int r[Arraysize];
unsigned long t[Arraysize];
int i;
String readingline, timeline;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
}

void loop() {
  for  (i=0; i<Arraysize; i=i+1)
  {
  // send the value of analog input 0:
  r[i] = analogRead(A0);
  t[i] = micros();
  }
    Serial.println("------------------------------------");
  for  (i=0; i<Arraysize; i=i+1)
  {
    readingline = "Iread = , ";
    readingline += r[i];
    timeline = "time = , ";
    timeline += t[i];
    readingline += ", ";
    readingline += timeline;
    Serial.println(readingline);
  }
delay(loopdelay);
}

Plotting r vs t can give you lots of info about your water heater current.

However it may be that the Hall sensor is a much better way to go!  No
wires need exposing!
I just ordered a couple they looked so good.

Martin
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