OpenEnergyMonitor

can someone see my mistake as i can not see why I cant get a reading for apparentpowersolar. the reading is 0.

apparentpower is working ok and i know the electronic circuit is ok here is my code.

//Basic energy monitoring sketch
//Authors: Trystan Lea, Eric Sandeen

//Licenced under GNU General Public Licence more details here
// openenergymonitor.org

//Sketch measures voltage and current.
//and then calculates useful values like real power,
//apparent power, powerfactor, Vrms, Irms.
#include <LiquidCrystal.h>

// Connections:
// rs (LCD pin 4) to Arduino pin 12
// rw (LCD pin 5) to Arduino pin 11
// enable (LCD pin 6) to Arduino pin 10
// LCD pin 15 to Arduino pin 13
// LCD pins d4, d5, d6, d7 to Arduino pins 5, 4, 3, 2
LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);

int backLight = 13; // pin 13 will control the backlight
//Setup variables
int numberOfSamples = 3000;

//Set Voltage and current input pins
int inPinV = 2;
int inPinI = 1;
int inPinIsolar = 0;
//Sanity check calibration method thanks to Eric Sandeen http://sandeen.net/wordpress
//See discussion here: http://openenergymonitor.org/emon/node/59
//Enter the values of your setup below

// Voltage is reduced both by wall xfmr & voltage divider
#define AC_WALL_VOLTAGE 235
#define AC_ADAPTER_VOLTAGE 9
// Ratio of the voltage divider in the circuit
#define AC_VOLTAGE_DIV_RATIO 11
// CT: Voltage depends on current, burden resistor, and turns
#define CT_BURDEN_RESISTOR 56
#define CT_TURNS 1500

//Calibration coeficients
//These need to be set in order to obtain accurate results
//Set the above values first and then calibrate futher using normal calibration method described on how to build it page.
double VCAL = 1.0;
double ICAL = 1.64;
double PHASECAL = 2.3;

int a = 9; // analog output pin with connected triak
int v = 0; // analog output value

// Initial gueses for ratios, modified by VCAL/ICAL tweaks
#define AC_ADAPTER_RATIO (AC_WALL_VOLTAGE / AC_ADAPTER_VOLTAGE)
double V_RATIO = AC_ADAPTER_RATIO * AC_VOLTAGE_DIV_RATIO * 5 / 1024 * VCAL;
double I_RATIO = (long double)CT_TURNS / CT_BURDEN_RESISTOR * 5 / 1024 * ICAL;
double I_RATIOsolar = (long double)CT_TURNS / CT_BURDEN_RESISTOR * 5 / 1024 * ICAL;
//Sample variables
int lastSampleV,lastSampleI,sampleV,sampleI,sampleIsolar,lastSampleIsolar;

//Filter variables
double lastFilteredV, lastFilteredI, filteredV, filteredI,lastFilteredIsolar,filteredIsolar;
double filterTemp;

//Stores the phase calibrated instantaneous voltage.
double shiftedV;

//Power calculation variables
double sqI,sqV,instP,sumI,sumV,sumP,sqIsolar,instpsolar,sumIsolar,sumpsolar;

//Useful value variables
double realPower,
apparentPower,
powerFactor,
Vrms,
realpowersolar,
apparentpowersolar,
powerFactorsolar,
realPowersolar,
apparentPowersolar,
Irmssolar,
sparepower,
sum,
Irms;

void setup()
{
Serial.begin(9600);
}

void loop()
{

for (int n=0; n<numberOfSamples; n++)
{

//Used for offset removal
lastSampleV=sampleV;
lastSampleI=sampleI;
lastSampleIsolar=sampleIsolar;
//Read in voltage and current samples.
sampleV = analogRead(inPinV);
sampleI = analogRead(inPinI);
sampleIsolar = analogRead(inPinIsolar);

//Used for offset removal
lastFilteredV = filteredV;
lastFilteredI = filteredI;
lastFilteredIsolar = filteredIsolar;
//Digital high pass filters to remove 2.5V DC offset.
filteredV = 0.996*(lastFilteredV+sampleV-lastSampleV);
filteredI = 0.996*(lastFilteredI+sampleI-lastSampleI);
filteredIsolar = 0.996*(lastFilteredIsolar+sampleIsolar-lastSampleIsolar);
//Phase calibration goes here.
shiftedV = lastFilteredV + PHASECAL * (filteredV - lastFilteredV);

//Root-mean-square method voltage
//1) square voltage values
sqV= filteredV * filteredV;
//2) sum
sumV += sqV;

//Root-mean-square method current
//1) square current values
sqI = filteredI * filteredI;
sqIsolar = filteredIsolar * filteredIsolar;
//2) sum
sumI += sqI;

//2) sum
sumIsolar += sqIsolar;
//Instantaneous Power
instP = shiftedV * filteredI;
instpsolar = shiftedV * filteredIsolar;
//Sum
sumP +=instP;
sumpsolar +=instpsolar;
}

//Calculation of the root of the mean of the voltage and current squared (rms)
//Calibration coeficients applied.
Vrms = V_RATIO*sqrt(sumV / numberOfSamples);
Irms = I_RATIO*sqrt(sumI / numberOfSamples);
Irmssolar = I_RATIOsolar*sqrt(sumIsolar / numberOfSamples);
//Calculation power values
realPower = V_RATIO*I_RATIO*sumP / numberOfSamples;
apparentPower = Vrms * Irms;
powerFactor = realPower / apparentPower;

realpowersolar = V_RATIO*I_RATIO*sumpsolar / numberOfSamples;
apparentpowersolar = Vrms * Irmssolar;
powerFactorsolar = realPowersolar / apparentPowersolar;

//Output to serial
//Serial.print(realPowersolar);
//Serial.print(' ');
//Serial.print(apparentPowersolar);
//Serial.print(' ');
//Serial.print(powerFactor);
//Serial.print(' ');
//Serial.print(Vrms);
//Serial.print(' ');
//Serial.println(Irmssolar);

//Reset accumulators
sumV = 0;
sumI = 0;
sumP = 0;
sumIsolar=0;

Serial.begin(115200);
pinMode(backLight, OUTPUT);
digitalWrite(backLight, 'high'); // turn backlight on. Replace 'HIGH' with 'LOW' to turn it off.
lcd.begin(16,2); // columns, rows. use 16,2 for a 16x2 LCD, etc.
lcd.clear(); // start with a blank screen
lcd.setCursor(0,0); // set cursor to column 0, row 0 (the first row)
lcd.print("Power Mains "); // change this text to whatever you like. keep it clean.
lcd.setCursor(0,1); // set cursor to column 0, row 1
lcd.print(double(apparentPower));lcd.print(" Watts");
delay(3000);
lcd.clear();
lcd.print("Power Solar ");
lcd.setCursor(0,1); // set cursor to column 0, row 1
lcd.print(double(apparentPowersolar));lcd.print(" Watts");
delay(3000);
sparepower=apparentpowersolar/apparentPower;
sum=3000/sparepower;
v=1024/sum;
analogWrite(a, v); // set analog out pin a to value v
delay(10);
//Reset values ready for next sample.
sumI=0.0;

// if you have a 4 row LCD, uncomment these lines to write to the bottom rows
// and change the lcd.begin() statement above.
//lcd.setCursor(0,2); // set cursor to column 0, row 2
//lcd.print("Row 3");
//lcd.setCursor(0,3); // set cursor to column 0, row 3
//lcd.print("Row 4");

}
 

 Amateur question:

1. What exactly is the meaning of non invasive?

2. Is there any other way to measure the input voltage except the AC AC adapter? (meaning other sensors etc.)

BTW awesome documentation of your work!

I need an ac-ac adaptor  but in Farnell  are No longer Manufactured is possible to use a Transformer (pcb version for example)   with Primary Voltages 230V  and Secondary 9V ? 

Please let me know 

Thanks in advance.

Regards 

Francesco.

Hi,

I am trying to design an arduino energy monitor, but I would like to measure the power consumption of each breaker. Therefore, My problem is that I do not know how to connect those multiple inputs to the Arduino. Do you know any method that can convert those multiple input into one for the arduino.

Thank you

Sorry this may look stupid, but I need an ac-ac adaptor for an EURO plugin (not UK) but in Farnell I only find ac-dc adaptors. Can you give me a help. Thanks in advance.

Hi TrystanLea,

What number of samples should I use?

Thanks.

Is it possible to build energy meter for 3 phase AC supply using arduino? If you have any idea please help me

I don't know these lines of codes.
Can someone explain to me these lines of code?

#define CT_BURDEN_RESISTOR 68
#define CT_TURNS 1012
#define AC_ADAPTER_VOLTAGE 15.2
#define AC_ADAPTER_RATIO (AC_WALL_VOLTAGE / AC_ADAPTER_VOLTAGE)

filteredV = 0.996*(lastFilteredV+sampleV-lastSampleV);
filteredI = 0.996*(lastFilteredI+sampleI-lastSampleI);

shiftedV = lastFilteredV + PHASECAL * (filteredV - lastFilteredV);

Hi,

If this is a dummy question please let me know:

Wouldn't be better to use a voltage reference CI to produce accurate bias voltage of 2.5v?

I mean, as you stated the bias voltage could be a source of noise. The choice of divider resistor values will also make the circuit more or less susceptible to noise and there is no way to predict the resistors value variance in function of ambient temperature. I think both resistor could also present different values and the cost of precision resistors could justify the reference stabilized CI.

Am I too wrong?

Regards,
Benito.

 Do the capacitors need to be electrolytic? Ceramic or tantalum with the same value are suitable?

I was having trouble calculating the burden resistor necessary for my 5 current sensors. I have 2 200-Amps on the mains coming into the house (I live in north-america), 2 100-Amps floating on different individual breakers and 1 30-Amps also floating.
Each sensor type has a different number of turns on the secondary coil. These figures are not published. I could guess the turn-ratio based on max current output from the manufacturers site. For example, the SCT-013-000 outputs a maximum current of 33 milli-Amp at 100 Amps. In theory. I have two of those, and they have different readings for a given current.

To calculate the burden resistor value for each sensor, I used a known amperage value load, from the reading of a Kill-A-Watt (two 400-Watts lamps) giving me 6.88 Amps.
So for the 200-Amps: I want to be able to monitor total energy usage for the whole house. In my home, each branch coming into the house can supply 100 Amps (for 200-Amps total). I want to maximize the sensitivity on the analog-to-digital pin of the Arduino. This is the key. If a 100 Amps current passes through the sensor, I want the analog pin to read 1024 (this is the maximum value that an analog pin can report, at 5 volts. The circuit suggested in these pages uses a voltage divider (two 10K resistors). So if no current passes through the sensor, you can expect to read 512 on the analog pin. To measure this reading on the analog pin, I used this piece of code in my energy monitor program:

tmpRead = analogRead(analog-pin-for-this-sensor);
if(tmpRead > maxRead)
maxRead = tmpRead;
Serial.print(maxRead);

where tmpRead and maxRead are integers

Since I want to measure a maximum of 100 Amps, I use 6.88/100 * 512 = 35. So I should choose a resistor that will give me a reading of 547 on the analog pin. Let's look at the formula:

D = Amp / max-Amp * analogRead(no-load)

or

know-amp-value-from-Kill-a-watt / maximum-amperage-expected-on-this-wire * mid-range-point-from-voltage-divider. So, in this case, a deflection of 35 on the analog pin corresponds to 6.88 Amps on the wire, related to an expected maximum of 100 Amps.

In practice, using the code above, I choose an analog pin and measure the idle value with any burden resistor (try any between 50 and 1000 Ohm). The value on the analog pin (maxRead above) should be close to 512 but can vary because of resistor precision in the voltage divider). I then use a known amperage (hence the Kill-A-Watt) and read the analog pin again. I choose a resistor that will give me a deflection of 35 (for my sensor) using a simple division.

As you can see, this is independent of the type of sensor used. Of course, you have to plan to measure a maximum amperage within the range of your sensor, and I would recommend a safety margin so you don’t overload the analog pin.

what is the part of filter v and filter i in the program do?? im getting all mixed up..

//Filter variables
double lastFilteredV, lastFilteredI, filteredV, filteredI;
double filterTemp;

double shiftedV; //instantaneous voltage saved

double sqI,sqV,instP,sumI,sumV,sumP; //calculation of power using the variables

void setup()
{
Serial.begin(9600);
}

void loop()
{

for (int n=0; n {

//Used for offset removal
lastSampleV=sampleV;
lastSampleI=sampleI;

//Read from analog in for sample of current and voltage
sampleV = analogRead(PinV);
sampleI = analogRead(PinI);

//Used for offset removal
lastFilteredV = filteredV;
lastFilteredI = filteredI;

//Digital high pass filters to remove 2.5V DC offset.
filteredV = 0.996*(lastFilteredV+sampleV-lastSampleV);
filteredI = 0.996*(lastFilteredI+sampleI-lastSampleI);

//Phase calibration goes here.
shiftedV = lastFilteredV + PFCAL * (filteredV - lastFilteredV);

//Root-mean-square method voltage
//1) square voltage values
sqV= filteredV * filteredV;
//2) sum
sumV += sqV;

//Root-mean-square method current
//1) square current values
sqI = filteredI * filteredI;
//2) sum
sumI += sqI;

//Instantaneous Power
instP = shiftedV * filteredI;
//Sum
sumP +=instP;
}

//Calculation of the root of the mean of the voltage and current squared (rms)
//Calibration coeficients applied.
Vrms = V_RATIO*sqrt(sumV / Samples);
Irms = I_RATIO*sqrt(sumI / Samples);

i just cant understand anything :/

im sry if im causing any trouble

can someone explain to me these two lines of code??
#define AC_WALL_VOLTAGE 122
#define AC_VOLTAGE_DIV_RATIO 11

hey guys,
if i chose r3 and r4 to be 10 k.....then which sizes are best for r1 and r2 in the voltage sensor part...
many thanks

may i ask.. which reasoning you followed in order to come up with the two circuits shown above?is there any principles to follow
thanks a lot

if I chose a 560 ohms burden resistor..than both the rvd's how much should they be??

the electronics of sensing current and voltage are both connected with the same arduino?? and which type of arduino they are connected to?? thanks

What is the best way to Join 2 efergy CT sensors in Series for Monitoring 2x 110V lines simultaniously ? Can I just have 2x 3.5mm female jack and join them like a series circuit. Also do I need to change the Burden resistor values to accomodate the fact that I have joined the CT sensors together ?

Hi. I have found this to be a great resource for getting me started monitoring power in my house. I have a few questions though:

I was planning on installing 24 of the "Non-invasive AC current sensor (30A max)" from seeedstudio to monitor each circuit. I would use some 4051 analog multiplexing chips so one arduino could monitor everything. Do you think I would be able to use one voltage divider+cap to bias the AC voltage coming from the CT's to bias all of the CT's?

Additionally, with regard to the bias circuit for monitoring current. I assume that you would want to bias the AC such that the bottom of the waveform is zero? For example, if the CT's I am looking at at 3v AC, I would want to bias those with 3v DC?

Thanks!

Hi,

Im planning to add one of these to my house, but have a quick question.

The burden resistor, can the value of this be less than 56R to allow measurement higher than 47Amps? (44ohm for 60Amps for example?)

Should I worry about the power rating of the burden resistor?

Cheers, and very impressive project!

Scott

Hi !

This is interesting and just what I have been looking for.

Where have you got (purchased) the CT sensor(s), shown in the Image 1 ?

Hi Trystan - A couple dumb questions from me about the arduino sketch...

1) What's the magic 0.996 value in the digital highpass filter? Could use a comment. :)

2) I'm thinking there should be a "nominal" VCAL just as a sanity check; assume I have XXX VAC at the wall, YY VAC coming out of the adapter, and YY/11 VAC in the middle of the voltage divider ... there should be some known/nominal VCAL given the wall voltage, the AC stepdown voltage, and the voltage divider properties, right?

We want to turn the arduino analog read value into the instantaneous Vac at the wall... So we have to scale it back up by all the factors involved.

(below assumes we've filtered out the DC offset already)

a) multiply by arduino scaling 5/1024 to convert the value read to the voltage read at the arduino.
b) multiply by voltage divider scaling (R1+R2)/R1 to get to the value at the AC adapter output
c) multiply by AC adapter scaling - (measured Vwall/Vadapter ratio) to get to the current wall value.

So, to go from (value read) to (wall voltage) I think we need to multiply by:

(Vwall/Vadapter)*((R1+R2)/R1)*(5/1024). For my case of 120VAC wall, 12VAC adapter, and 1/11 (10:1) reduction voltage divider, this would give me about 0.537 as a VCAL starting point, does that sound right?

If that all sounds right, maybe it'd be nice to have variables for the above values in the sketch, and scale by that initially, then let VCAL do the final tweaking; IOW VCAL would usually be closer to 1.0

(However, above only works if PHASECAL is 1.0 ... OTOH Vrms should be whatever it is, regardless of the phase calibration, right? So not quite sure how/why PHASECAL affects the measured Vrms, I guess it's because we're sampling over time and have to "scale" the voltage in the loop to accomidate the net effect of the phase shift...?)

Thanks,
-Eric