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--- amc2022:grouph:link [2022/08/10 12:30] – created gustavo001
+++ amc2022:grouph:link [2023/01/05 14:38] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 ===== Build ======
-===== Code ======
+{{ :amc2022:grouph:voltage_divider.jpeg?nolink&400 |}}
-===== Description ======
+| //**figure 5.1**// Setup showing the connections for battery voltage reading on ESP32 |
+===== Schematics =====
+{{ :amc2022:grouph:batt_schematics.png?nolink&400 |}}
+| //**figure 5.2**// Schematic for battery voltage reading |
+===== Code & Description ======
+<code c++>
+*//Reading of voltage is done by the Analog Pin reader.
+*//Because the max input voltage on the pins is 3.3 V we cant directly read the 9V battery voltage.
+ int potPin = A0;         // Analog pin has to be ADC 1, because ADC 2 are used by wifi and wont work
+int potValue;
+float voltage =0;         // float because its a decimal number not integer
+float battery_percent;
+void setup() {
+  Serial.begin(115200);
+  {
+  potValue = analogRead(potPin);
+  float voltage = (3.3/4095.0) * potValue * 2.73;
+  *//Resistors and other components can have a varying number of outputs, although they are usually minimal
+  *//additional calibration has to be done in order to get accurate readings
+  *//We have found that the use of a multimeter will help in determining the values that will provide best outcomes
+  *//Because we have different boards, resistors and setups, the final code could have alterations in the calibrating numbers
+  Serial.print("potValue:");
+  Serial.print(potValue);
+*//While the serial monitor output can be changed, we are more interested is in the overall result which is transmitted
+*//to Grafana for easy access
+  Serial.print(" Voltage:");
+  Serial.print(voltage);
+  Serial.println("V");
+  battery_percent = mapfloat(voltage, 3.0, 9.0, 0 , 100); // min value cut off at 6V and maximum voltage is 9V
+  if (battery_percent > 100)
+  {
+    battery_percent = 100;
+  }
+  if (battery_percent < 0)
+  {
+    battery_percent = 0;
+  }
+*//For the conversion between the actual Analog reading to a percentage we use a mapFloat function
+*//It uses the input range from the analog sensor to produce another set of useful values
+*//float values will allows to get decimal numbers and a more accurate reading
+*//We use a the min voltage value, then max voltage value, and min percentage and max percentage
+*//Then we ask the program to give us the corresponding percentage value within the parameters
+  Serial.print("Battery Percentage = ");
+  Serial.println(battery_percent);
+  if (voltage > 7.0 && voltage < 8.2)            // THIS VALUES HAVE TO CHANGE ACCOrDING TO SOURCE
+  {Serial.print("Low bat");                      // USE VOLTMETER TO FIND THE ACCURATE VOLTAGE
+  }
+  if (voltage <6.5)                              //cut-off value is at 5.4V according to specification , we use 6V
+  {Serial.print("Replace Battery");
+  }
+  delay(1000);
+*//We have included a notification that will tell us what is going on with the voltage and overall battery status
+*//We include a parameter that will produce 2 warning signs:
+*// LOW BAT means that our battery is within 7 to 8.2V
+*// REPLACE BATTERY means voltage has dropped below 6.5V, number obtained from data sheet
+}
+}
+ float mapfloat(float x, float in_min, float in_max, float out_min, float out_max)
+{
+  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
+}
+*//here we include the parameters and equation that will serve as the backbone for the mapFloat function above.
+void loop()
+{
+}
+*// NO LOOP NEEDED,,, ONE VALUE WITH WARNING SHOULD BE DISPLAYED ON GRAFANA
+</code>
+===== Issues & Characteristics ======
+The actual voltage will not be 100% accurate because the ADC pins have a non-linear behavior. This means according to the Figure # down below that, above a certain threshold the reading will produce equal inputs, thus we consider that from 3 to 3.3V the battery is at a 100% charge.
+Additionally we can see that the discharge behavior of the battery we are using, which is a model 6F22 is a curve that has a specific equation, we could find the curve's equation and use it to better represent the discharge values, however since we plan to upgrade our battery system we purposely used a simpler version in our code to achieve good enough results.
+^ {{ :amc2022:grouph:9v_battery_.png?400&nolink }}  ^ {{ :amc2022:grouph:adc_behaviour.png?nolink&600 |}}  ^
+|  //**figure 5.3**// Graph depicting battery discharge for battery model 6F22 9v Source:https://www.mega-piles.com/im/PANASONIC-6F22-9V-CARBONE-ZINC_550.pdf                                                 | //**figure 5.4**// Graph depicting ADC voltage VS reading behavior for ESP32 micro controller. Source:https://microcontrollerslab.com/adc-esp32-measuring-voltage-example/                                                     |
 ===== Results ======
+{{ :amc2022:grouph:voltage_divider_serialmonitor.png?nolink&400 |}}