4051 demux pots, double readings?

Using Arduino Programming Questions
1

Hi,

i've used this 4051 many times before with the same code and it has always worked fine.
until today, i finished the wiring on my latest project and only half of the pots work.
i've checked the wires and i cant seem to find the problem there.
but maybe somebody had had this problem before so i thought i should ask.

what happens is that when i turn pot 1, it will show the exact same value in the serial monitor for pot 1 and pot 4. pot 4 doesn't work.

if i turn pot 2, it will show the exact same value in the serial monitor for pot 2 and pot 3. pot 3 doens't work.

any ideas?

int MuxPin1=2; 
int MuxPin2=4;
int MuxPin3=3;
int AnaInPin1=0;
int AnaInPin2=1;

//Declare variables
int MuxVal1 = 0; 
int MuxVal2 = 0; 
int MuxVal3 = 0; 
int BinVal = 0; 
int N = 0; 

//BinPat is used for figuring out the High / Low (1/0) values of the MUX control pins
int BinPat [] = {000, 1, 10, 11, 100, 101, 110, 111};

//The PotValues array is used for storing the 16 vlues read from the potentiometers
int PotValues [] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};

void setup()
{ 
  //Initialize digital pins and serial communication speed
  pinMode(MuxPin1, OUTPUT);
  pinMode(MuxPin2, OUTPUT);
  pinMode(MuxPin3, OUTPUT); 
  Serial.begin(9600);
} 

void loop() {
  readPotValues();
  sendPotValues();
  delay (10);
}

void readPotValues()
{
for (N=0; N<=7; N++) 
    {
      BinVal = BinPat[N];      
      MuxVal1 = BinVal & 0x01;
      MuxVal2 = (BinVal>>1) & 0x01;
      MuxVal3 = (BinVal>>2) & 0x01;
      digitalWrite(MuxPin1, MuxVal1);
      digitalWrite(MuxPin2, MuxVal2);
      digitalWrite(MuxPin3, MuxVal3);
      PotValues[N]=analogRead(AnaInPin1) / 4 ;
      PotValues[N + 8]=analogRead(AnaInPin2) / 4;   
    }  
}

    

void sendPotValues()
{
for (N=0; N<=14; N++) 
    {
      Serial.print(PotValues[N]);
      Serial.print(',');
    }  
    Serial.println(PotValues[15]); 
}
2

Your "BinPat"s are in decimal. Make them binary constants for better effect:

int BinPat [] = {000, 1, 10, 11, 100, 101, 110, 111};

should probably be:

const byte BinPat [] = {0b000, 0b001, 0b010, 0b011, 0b100, 0b101, 0b110, 0b111};

which is the same as:

const byte BinPat [] = {0, 1, 2, 3, 4, 5, 6, 7};

which means that "BinPat[N]" is equal to "N" so it isn't of much use.

3

johnwasser:
Your "BinPat"s are in decimal. Make them binary constants for better effect:

int BinPat [] = {000, 1, 10, 11, 100, 101, 110, 111};

should probably be:

const byte BinPat [] = {0b000, 0b001, 0b010, 0b011, 0b100, 0b101, 0b110, 0b111};

which is the same as:

const byte BinPat [] = {0, 1, 2, 3, 4, 5, 6, 7};

which means that "BinPat[N]" is equal to "N" so it isn't of much use.

Thanx for the hint. :slight_smile: i've been checking my wiring the last 3 hours and it seems there is some kind of short some where, but i can't find it.. i'll keep you posted...