Programming with Arduino

Exercise 1—Using a Push Button

Switches complete your circuits:

Using a NO (normally on) push button, add the following to your breadboard:

These little switches are a 1/4" on each side, and can plug directly into a breadboard. These mechanical devices have 4 legs, which may make you think that there are 4 wires that are switched on and off, but in fact, two on each side are actually connected together inside. So really, this switch is just a 2-wire switch.

Normally, the two wires are disconnected (normally open) but when you press the little button on top, they are mechanically connected.

To get the buttons to sit better in the protoshield, you may want to straighten out the legs (just squish them with a pair of pliers) so that they look like the button on the left.

Adding the Microcontroller

Now connect the led and the switch to the chip:
NO Push button

The Arduino chip has uncommitted inputs. That is, when an I/O pin is not connected and acting as an input, it cannot be assured to be either HIGH or LOW. Pull-up and pull-down resistors are needed to commit the input to the non-active (open) state for switches.

When the button IS NOT pressed (open), P10 will sense Vss (0V, LOW, 0) because it is pulled-down to Vss.
When PB1 IS pressed (closed), P10 will sense Vdd (5V, HIGH, 1) making it Active-High.

/* using a push button*/
int LED1=8;
int BTN1=10;
void setup(){
    pinMode(LED1,OUTPUT);
    pinMode(BTN1,INPUT);
}
 void loop(){
 if (digitalRead(BTN1)==0){
        digitalWrite(LED1,LOW);
     } else if  (digitalRead(BTN1)==1){
        digitalWrite(LED1,HIGH);
     }
 }

This code can be rewritten:

/* using a push button*/
int LED1=8;
int BTN1=10;
void setup(){
    pinMode(LED1,OUTPUT);
    pinMode(BTN1,INPUT);
}
 void loop(){
 if (!digitalRead(BTN1)){
        digitalWrite(LED1,LOW);
     } else if  (digitalRead(BTN1)){
        digitalWrite(LED1,HIGH);
     }
 }

or:

/* using a push button*/
int LED1=8;
int BTN1=10;
void setup(){
    pinMode(LED1,OUTPUT);
    pinMode(BTN1,INPUT);
}
 void loop(){
     digitalWrite(LED1,digitalRead(BTN1);  
 }

Instead of a push button create a custom button (water, penny, stapler, sheets of metal, etc).