Lesson 9--Microduino "DIY Multimeter"

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Previously, we introduced analogRead() and its return values of 0~1024. In this lesson, we will use the analog port of Microduino-Core to make a multimeter with the range of 0-5 V.

Important: The design of this experiment does not have an effective protection circuit. Please do not use more than two AA batteries and do not use the circuit to measure a lithium battery or any other power supply!



Experiment Schematic



float temp;   // Define a float variable temp to save data.
void setup()
  Serial.begin(9600);     //Set baud rate 9600
void loop()
  int V1 = analogRead(A0);                    
// Read the voltage data from A0 and store it in variable V1. The voltage range is 0-5V and returns values 0-1024. 
  float vol = V1*(5.0 / 1023.0);               
//Convert the V1 to the voltage value and store it in vol
  if (vol == temp)                             
//Use to filter duplicate data, Only the voltage value and the last isn't same then output the value.
    temp = vol;                               //Compared, then store in temp variable "temp"
    Serial.print(vol);                       //Serial output voltage, nowrap  
    Serial.println(" V");                    //Serial output character "V", and wrap
    temp = vol;
    delay(1000);                           //Wait for 1s, use to refresh the data

We didn't use the map() function in this example, but you can try it yourself!


When the measured voltage changes, refresh the data every second. It is normal if there is a difference between two measurements of the same battery. This is because this is still simply a low accuracy test. If you need a high accuracy test, you can take a look at: http://www.hacktronics.com/Tutorials/arduino-current-sensor.html