LED bar graph script not working

Question

I have LED bar graph on pins 2-11. Eventually I want to use a voltage divider to figure out the amount of voltage left in a power supply. Currently, this script should set the number of LEDs on the bar graph based on round((v_actual/v_reference)*10), I am just using some placeholder numbers in the mean time to test this portion of the script e.g. v_actual of 5 and v_reference of 10. However, the convert variable keeps printing 0. I've checked that the other variables were passing and they are. What is the issue here?

#include <Wire.h>
int ledBarNum = 10; // # of leds
int vref = 10; // max voltage of power supply
void setup(){
 pinMode(2, OUTPUT);
 pinMode(3, OUTPUT);
 pinMode(4, OUTPUT);
 pinMode(5, OUTPUT);
 pinMode(6, OUTPUT);
 pinMode(7, OUTPUT);
 pinMode(8, OUTPUT);
 pinMode(9, OUTPUT);
 pinMode(10, OUTPUT);
 pinMode(11, OUTPUT);
}
void loop() {
 ledBarSetup(5);
}
void ledBarSetup(int v) {
 // logic vref=8; vactual or v = 4; (4/8)*10 = 2 
 // e.g. number of leds we need to light up to represent the total amt left
 Serial.println(v);
 Serial.println(vref);
 int convert = round((v/vref)*10);
 Serial.println(convert);
 ledBar(convert);
}
void ledBar(int n) {
 int startingPin = 2;
 for (int thisPin = 2; thisPin < ledBarNum; thisPin++) {
 if (thisPin <= n) {
 digitalWrite(thisPin, HIGH);
 } else {
 digitalWrite(thisPin, LOW);
 }
 }
}

• Gerben: In integer math, 5/10 is equal to 0.

Answer 1

Both v and vref are integers, which means that integer division will be performed. if v is ever less than vref then the result will be 0. Multiply first, then divide.

• Alex: ah yes I suppose I should have looked up the diff between int and float in arduino. Was completely unaware of this. Doing the multiply then divide method! (v*10/vref)