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Measure any AC current with ACS712 and Arduino + LCD / OLED

 

PLEASE BE CAREFUL IF YOU’RE USING THE POWER LINE

       Hello, and welcome to another tutorial, this one is about measuring Alternating Current (AC), using ACS712 I’m using the 30Amps version which is ACS712 30A, and our lovely Arduino Uno board, I tried to add an OLED screen but unfortunately ended up breaking it while shooting the tutorial so I switched to the LCD, but below you’ll find the wiring and codes for both versions.

And by “Any AC…” I mean that we gonna see a code/library that works for all signal types not only sinewaves one, and our Ammeter will be able to calculate the TRUE ROOT MEAN SQUARE. And note that the sensor uses the Hall Effect (production of a voltage difference across an electrical conductor, transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current)

You can combine this project with this one: Easy measure of AC Voltage using Arduino and ZMPT101B

Tests will be done on an incandescent light bulb, controlled by a light dimmer in series with a reference multimeter and the ACS712 current sensor module.

Wiring all

Here’s the plan:

  • First we need to interface our module with the Arduino board and check the signal shape when the dimmer is ON – Full Cycle – Half Cycle.
  • Then we gonna chech a simple code that doesn’t require any library, but it works only with Sinewaves signal (it will be tested).
  • After that we gonna see the code that will measure the TRMS of the AC, and use the LCD.

Parts

Please be carfeul when chosing the ACS712, don’t try to play it safe like I did (by purchasing a 30Amps version), this will just give big fluctuation when you try to use it for a domestic use or small amps applications, so here for me a 5A or 10A version would have been fine.
Also note that 30A or 20A … will affect your calibrations too, but it’s explained how to calibrate in video and in codes comments.

Those are the parts I used, you can replace the UNO with any compatible board, or that LCD i²c with an OLED or any display you prefer.

Test 1

Wiring

 

test 1_bblolz.png
Direct test

Code

/*This code works with ACS712 Current sensor, it permits to read the raw data
  It's better to use it with Serial Plotter
  More details on www.surtrtech.com
*/

#define Current_sensor A0  //The sensor analog input pin

float i;


void setup() {

Serial.begin(9600);
pinMode(Current_sensor, INPUT);

}

void loop() {
  i = analogRead(Current_sensor);
  Serial.println(i);
  delay(100);                     //Modifying or removing the delay will change the way the signal is shown 
                                  //set it until you get the correct sinewave shap

}

 

 

Results

Upload the code and launch the serial plotter, you should be able to see a sinewave like signal, the red line shows when I turned down the dimmer and the current started having that shape that you usually find in a triac.

Test_1
Direct wiring and show of the serial plotter

Test 2

Now if you want to measure the current using the code above only, you’ll get values around 512 – 511, they don’t reflect the RMS value at all. So to measure the signal RMS value we gonna keep the same wiring as above but now we need another code that can calculate the RMS.

Code

Here you can download the second code from Drive: Download code .ino here

(I can’t write all the code here, because it won’t display well, and will give you errors if you try to copy and compile it).

Results

Test_2

As you can see the values on the left (RMS) are the same as the value measured by the multimeter, on the right those are Peak to Peak values, and note that the dimmer is at full cycle as I’m using 75W bulb and 230VAC/50Hz.

!!!!!!!!!!!!!!!!     BUT   !!!!!!!!!!!!!!!!!!!!!

Test_3

Here I turned all the way down my light dimmer, which means I’m approximately around 1/4 of a cycle, the multimeter is giving me 0.21A but my code gives me 0.36A, the code still measures from Peak to Peak, but as you can see above my signal is not linear when I turn the dimmer all the way down.

And that’s the difference between a TRMS measuring and a measuring that works only with sinewaves signal.

Test 3

Now you see the problem of the code above, but fortunately there’s a library to the rescue, I really appreciate that library for all the work it does because as you know if you want to calculate a RMS value you need to use Integral Calculus, and that’s way difficult to achieve on an electronic development board, you can check the library cpp file to see what methods are used like the “Average” “Sigma”… Things related to statistics/probabilities ….

Library

Here you can download the Filters library: Download the library here.

Wiring

For the wiring we can keep everything the same as above.

Code

Here you can download the Code I used: Download the code here. The code contains a lot of comment to make it easy for you.

Results

The correct results are on the middle, the left ones are without calibration, and the right ones are used to demonstrate how to calibrate (check the video)

Test_4_1
At full cycle
Test_4_2
At 1/4 of a cylce the code doesn’t have any problem to measure non linear signals

As you saw the huge difference between the two codes response to a non linear signal but the second one act as a TRMS multimeter.

Test 4

Here we keep the same things all we do is instead of using the serial monitor we can use LCD or OLED

Wirings

 

test lcd_bb
Using the LCD

 

test oled_bb
Using the OLED

Codes

Here you can download the codes :

Libraries

OLED i²c display Adafruit libraries: – https://github.com/adafruit/Adafruit_SSD1306

https://github.com/adafruit/Adafruit-GFX-Library

LCD i²c library you can Download it here.

Result

Test_5

This is the only test I could do because I broke my OLED screen while trying to shoot the video tutorial 😦

Overall this works the same way as we saw before it just displays it on a LCD i²c screen.

That’s all folks, I hope you like this tutorial don’t forget to like the video tutorial and subscribe to surtrtech channel to show support, thank you very much.

Yassine View All

Automation and Electrical Engineer, Electronics amateur trying to share my little projects.

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