Calibration error in ZMPT101B i didn"t get the sine wave using arduino

[ashwin21]

Hi everyone
Initially i CALBRIATE the value in first step.. so didn"t get proper sine value while i turning 100k pot also
Connection Arduino to zmpt101b
5V TO VCC
A1 TO OUT (I Checked here in multimeter 2.53v in zmpt101b)
GRD TO GRD
product link zmpt101b

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

  // Set analoge pin to input
  pinMode(A1, INPUT);
}

void loop() {
  // Read analog input
  Serial.println(analogRead(A1));
  delay(20);
}

Here i should get the sinewave but inot geeting properly

please help me to crack this guys and thank you so much

[jim-p]

Try this

void setup() {
  Serial.begin(115200);

  // Set analoge pin to input
  pinMode(A1, INPUT);
}

void loop() {
  // Read analog input
  Serial.print(analogRead(A1));
  Serial.println();
  delayMicroseconds(800);
}

[jim-p]

Which IDE version are you using?

[Wawa]

@ashwin21

delay(20);

What do you think that does.
delay(20); // wait a full 50Hz sine wave, and measure at the exact same point of the wave
Successive voltage sample will be almost the same as the first one, being at the top of the wave or at zero crossing.
Leo..

[ashwin21]

im using Arduino idle1.8.19 older version

[johnerrington]

@ashwin21

Serial.begin(9600);

are you really using a teletype? if not why not use a faster baud rate?

Have you considered how many samples you need to take in 1 cycle to get a sensible wave shape?
(HINT - its NOT 2)

skillbank: Introduction to Data conversion

[JohnLincoln]

Ashwin21,
In order to show you the issues mentioned in Johnerrington's post #7, I've modified your code slightly to turn a pin high just before your analogRead, and low again after the analogRead, so that the analogReads can be seen on an oscilloscope.
I used direct port manipulation for negligible effect on the timing of the code.

int monitorPin = 12;

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

  // Set analoge pin to input
  pinMode(A1, INPUT);
  // Set monitor pin to output
  pinMode(monitorPin, OUTPUT);
}

void loop() {
  // take monitor pin high
  PORTB = B00010000;
  // Read analog input
  Serial.println(analogRead(A1));
  // take monitor pin low
  PORTB = B00000000;
  delay(20);
}

Here are the results on an oscilloscope .
The yellow trace is a 50Hz, 4V peak to peak sinewave.
The red trace is the serial printing (decoded below the trace).
The blue trace is the pin that is high during the analogRead.

You can see that you only take one reading/sample for each cycle of the 50Hz signal. The sampling point is slightly later each cycle. This can be seen on the decoded serial printing: 575, 610, 645.

And here are the results of jim-p's code modified in the same way.
You can see that Jim takes multiple samples in each cycle of the 50Hz signal.

Here are the results on the Serial Plotter.
Your code:

This plot appears to show 7 cycles in a time of approximately (500 x 20ms) = 10s.
This corresponds to an 'apparent' frequency of just over 1.4Hz - not the actual 50Hz input frequency. This is the aliasing that John Errington mentions.

Here is jim-p's code on the Serial Plotter:

The horizontal scale is now different, but correctly displays 27 cycles in just over 540ms.

[JohnLincoln]

@johnerrington

are you really using a teletype?

I remember using a teletype at University to talk to the department of Electrical and Electronic Engineering's digital computer.
As an undergraduate we never actually saw the computer itself. (I was shown it briefly, during my interview for going there.)

Five years later there were computers in schools.