# What is the proper and up to date method for multiplexing digital inputs?

So Im following the diagram here for wiring up a MC14067BCP: http://fluidforms.eu/docs/MultiplexedArduinoWiringDiagram.pdf

The only difference being that I am doing one set of 16 sensors and not four. Additionally, my sensors are 5k - 250k LDRs (light sensitive resistors) that I have connected to ground on the end opposite of those connected to the connections shown in the diagram above.

When I run my sketch, the serial line shows output that is similar to what would be shown if no wires were connected to my analog in at all. (see the question here to see what I mean by that: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1238854387) This is really stressing me out and it would be amazing if someone could enlighten me as to what is going on.

Here is my code:

int CONTROLpin1 = 2;
int CONTROLpin2 = 3;
int CONTROLpin3 = 4;
int CONTROLpin4 = 5;
int analogPin = 0;

// Variables:

void sendCommand(int value) {
Serial.println(value);
}

void setup() {
//  set the states of the I/O pins:
pinMode(CONTROLpin1, OUTPUT);
pinMode(CONTROLpin2, OUTPUT);
pinMode(CONTROLpin3, OUTPUT);
pinMode(CONTROLpin4, OUTPUT);
pinMode(analogPin, INPUT);

Serial.begin(9600);
}

void loop() {
int i;
for (i=0; i <16; i++) {

// set control pins on the multiplexers

Serial.println(i); // print which pin we are on
sendCommand(actualSensorValue);

delay(1000);
}
}


Additionally, I have tried cutting it down to the bare minimum and only wiring up a single sensor. When looking at the output, there appears to be no change. Here is a picture of the bare bones wiring:

(but to be clear my end goal is still the diagram at the top of this post).

• Please post a schematic of your setup – clabacchio May 2 '12 at 8:20
• @clabacchio it's the first link – bradleygriffith May 2 '12 at 8:24
• Can you post a schematic of your single sensor setup ? – Rocketmagnet May 2 '12 at 8:27
• will a picture do? i.imgur.com/IaTD1.jpg – bradleygriffith May 2 '12 at 8:30
• That's the schematic you are trying to reproduce, but you are making changes, so I was asking the actual schematic. A picture may do, but the schematic is better – clabacchio May 2 '12 at 9:01