Lesson 9--Microduino "DIY Multimeter"

Language	English

Objective 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! Equipment Microduino-Core Microduino-FT232R Other hardware equipment 1x AA Battery 1x Box of breadboard jumper wires 1x Breadboard 1x 1kΩ resistor 1x USB Data cable Experiment Schematic Program 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" } else { 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! Result 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 Video https://www.youtube.com/watch?v=bhaj_QhRE-Q