Solar Monitoring System

ESP-12 based Solar Panel Monitoring System

This system helps you to remotely monitor the power of  your solar panels, batteries and the DC load with a smartphone from anywhere.
It’s based on the Nodemcu ESP-12 WiFi module and Blynk application. The battery and solar voltage with the temperature will be displayed. It’s also possible by using buttons on installed app to decide witch batteries should be charged.

This tutorial try to shows step-by-step how to make it.

  1. The solar panels output up to 35V with direct sun.
  2. The solar panels charger is positive ground controller. (And this provide me a lot problems with negative grounded ESP.)
  3. Two car batteries.

Hardware Requirements

  • ESP-12 WiFi module
  • 2 x VOLTAGE SENSOR (INA219) for Batteries (from 0 to 26 V)
  • VOLTAGE SENSOR (INA229) for Solar (not more needed, replaced with voltage divider)
  • 2 x ACS712 Current sensing Module in 30A (Available in 5A, 20A and 30A)
  • 4 x resistors used as voltage divider
  • 2 x 4 Channels ADS1115 16 Bit ADC Board (I2C, address 0x48)
  • Temperature  Sensor Devices:
    • LM35 Integrated Circuit (range of 0-100°C)  (Not used in version 1)
    • DHT11 Temperature/Humidity sensor (Used to measure the inside temperature around batteries.)
    • BMP280 Barometric Pressure + Temperature Sensor  (Not used in version 1)
    • 1 x DS18b20 Temperature sensors (Used to measure the outside temperature.)
  • Power supply 3.3V for ESP module and 5V for the others such as 2xACS712 modules
  • Two Channel Relays 

The voltage of batteries can be messure by INA229 module. (but I replaced the sensors with voltage divider)
The maximum input voltage for INA219 is 26 V and  for INA229 is limited to 36 V. 
The devices use a 3 to 5.5-V supply and can be assigned to 4 different I2C addresses (0x40, 0x41, 0x42, 0x43).

#include "Wire.h";
#include "Adafruit_INA219.h";

Adafruit_INA219 ina219_B1;
Adafruit_INA219 ina219_B2(0x41);

void setup(void) {
   ina219_B1.begin(); // Initialize first board (default address 0x40)
   ina219_B2.begin(); // Initialize second board with the address 0x41
}

At this moment I’m using voltage dividers to measure the voltages in my project.

To measure the currents I’m using two ACS712 modules (hall effect device) .
One sensor measures the current of battery charger and the other one the current of the load.
The ACS712 has to be fed with 5V and the analog outputs voltage is proportional to measured current on the sensing terminals.

The sensor is bi-directional so it will give 2.5V output even if not current is flowing through it.  (below my calculation to get current values).
The module gives a sensitivity of 0.1V/A in 20A and available in 5A, 20A and 30A.

The ADS1115 is a 16-bit analog-to-digital converter and  I’m using to read the voltage from Hall sensor. 
The ADS1115 can be addressed with one of four I2C addresses. (0x48, 0x49, 0x4a, 0x4b).

ADS1115 6-bit analog-to-digital converter

ADS1115 16-bit analog to digital converter

Voltage Supply (Vdd): 2 ~ 5V
Measurement range: -300mV to Vdd+300mV
Data rate: 8 ~ 860 SPS
Active current: ~150uA (200uA max)

I’m using ADS1115  in two channel and in GAIN_ONE mode.
In GAIN_ONE mode the voltage can be measured up to maximum 4V  and provides a resolution of 0.125mV per bit.  (4.096 volts / 32767 bits )

I calculated the ADC in gain_one program mode together with ACS as followed:

calculation the ADC in gain_one program mode

calculation the ADC in gain_one program mode

We can not connect up to a 3.3V voltage an ADC input!
So we using a voltage divider to bring the voltage between 0V and 3.3V.

R1 = 10k, R2 = 20k
R2/(R1 + R2) => 0.66 => 1/0.66=1.51
ADC(MaxVin) = 0.66 * 5V = 3.3V
The ACS sensor have zero current by 2.5V.  This corresponds to the voltage 1.65V at ADC and also 13200 bits.
So I can calculate the current as followed:
multiplier = 0.000125F; /* ADS1115 @ +/- 4.096V gain_1 (16-bit results) */
aMultiplier = multiplier * ( 1/0.66)
Now we read the input AIN2 digital value of 16 bits ADC

adc = ads.readADC_SingleEnded(2);   
current = (adc - 13200 ) * aMultiplier ) / (2.5/20)); // in Ampere

#include "Wire.h";
#include "Adafruit_ADS1015.h";

Adafruit_ADS1115 ads48(0x48); // use for the 16-bit
Adafruit_ADS1115 ads49(0x49); // use for the 16-bit

void setup(void) {
   // ads.setGain(GAIN_ONE);  // 1x gain +/- 4.096V 1 bit = 2mV 0.125mV
   ads48.begin();
   ads49.begin();
   ...
}
...
int16_t adc = ads48.readADC_SingleEnded(2);
float volt = (adc * 0.125) / 1000 * 4.4;
Serial.print("Battery Voltage:"); 
Serial.print(volt); Serial.println(" V");

High temperature can damaged the batteries.

BME280 Barometric Pressure

BME280 Barometric Pressure

The purpose to use DHT11 or DS18B20 temperature sensors is to enable us to compare the battery temperature with the environment temperature.
I’m using one sensor for environment and one for battery.
The mobile app will display the temperatures and humidity.

BME280 Barometric Pressure + Temperature Sensor
BME280 is the next-generation digital temperature, humidity and pressure sensor manufactured by Bosch.
The operating voltage of the BME280 module is from 3.3V to 5V
The default I2C address of the BME280 module is 0x76 and can be changed to 0x77 with the solder jumper on the chip.

#include "Wire.h";
#include "Adafruit_Sensor.h";
#include "SparkFunBME280.h"
#include "math.h"

BME280 bme;

void setup(void) {
  Serial.begin(115200);
  Serial.println(F("Initialize BME280 with 0x76."));
  bme.settings.commInterface = I2C_MODE;
  bme.settings.I2CAddress = 0x76;
  bme.settings.runMode = 3; //Normal mode
  bme.settings.tStandby = 0; // 0, 0.5ms
  bme.settings.filter = 0; //0, filter off
  bme.settings.tempOverSample = 1;
  bme.settings.pressOverSample = 1;
  bme.settings.humidOverSample = 1;
  Serial.println(bme.begin(), HEX);
  ...
}

float T = bme.readTempC();
Serial.print("Temperatur: "); Serial.print(T,1); Serial.println(" °C");
float pH = bme.readFloatPressure()/100.0;
Serial.print("Atmospheric pressure at current location: "); Serial.print(pH, 1); Serial.println(" hPa");
float H = bme.readFloatAltitudeMeters();
Serial.print("Altitude: "); Serial.print(H,1); Serial.println("m");


The whole system (The draft version have problems with them positive ground charger)

Schematic Diagram (Voltage sensors are replaced by voltage dividers)

Schematic Diagram (Voltage sensors are replaced by voltage dividers)

– It’s also nice to have a light sensor to read the daylight intensity.
I’m still working on it.
I will test it as soon as weather will be kind with me :) and hop to able some photos of assembly.

Schematic and Wiring Diagram: (next generation)

Common Positive Solar Charge Controller

My controller is positive-grounded. It means the positive of solar, battery and load are hard-wired together inside the unit which makes my life hard.
Therefore, you should not use the USB charging ports to power the ESP-12 board.

I removed INA219 and INA226 sensors and replaced them with voltage divider and don’t longer use the small USB charging of regulater to power the ESP-12 board. To power the board, I’m using a 12/24 volt to 5/3.3 volt step down module.

You are welcome to download or review the program code (ESP-12E/Solar Monitor System) from here.
The code is working fine since 2 weeks with a good result.

Visualizing the data on a Blynk Android App
The system is accessible through a Blynk app.
The switching the batteries will sent from app by using virtual pins and the data can be easily access on app.

The chart of the data

The chart of the data

Blynk Interface

Screenshot of Smartphone Blynk Interface

Complete circuit diagram for Solar Monitoring is given below:


Continue …


Installing the ESP8266 Arduino Addon
To begin, we’ll need to update the board manager in Arduino,
A- Go to the File > Preferences and add the URL
http://arduino.esp8266.com/stable/package_esp8266com_index.json”  into the “Additional Board Manager”
B- Navigate to the Board Manager by going to Tools > Boards > Boards Manager. and look for esp8266 then select Install.

 NodeMCU 1.0 (ESP-12E Module)

Continue …

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