switches & whiskers on the Arduino living with the lab lever arm switches mounted to Arduino © 2012 David Hall

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the switches long lever with three electrical terminals can be wired as normally open (electricity flows only when switch pressed) can be wired as normally closed (electricity stops flowing when switch pressed) used with inch quick disconnect terminals 3 living with the lab

4 wiring when the switch is not pressed, electricity can pass through the normally closed (NC) path when the switch is pressed, electricity can pass through the normally open (NO) path

use a digital input to sense when switch is on or off 5 living with the lab ANALOG RESET 3V3 5V Gnd Vin AREF GND DIGITAL POWER 10k  switch switch status voltage at pin 7 status of digital input 7 0V (no power applied) 5V (direct connection to power) HIGH LOW closed (pressed) open (not pressed) digitalRead(7) check status of pin 7 using...

6 living with the lab why the 10kΩ resistor? ANALOG RESET 3V3 5V Gnd Vin AREF GND DIGITAL POWER 10k  switch using a large resistance limits the current so that we don’t waste electricity... any resistor will do, but there’s no sense in wasting power

7 hooking things up on your robot living with the lab space is tight, and it’s easy to break the quick disconnect terminals (can solder them if desired) connect wires to the common and normally open terminals on the switch

8 tools a wire stripper and some sort of crimping tool are needed (can also crudely crimp using a vise) living with the lab

9 completing the circuit on the breadboard to prevent wires from coming loose to make it easier to see what’s going on (easier to troubleshoot) living with the lab try to keep the wiring tidy... violet leads go to +5V source white and red leads provide digital input one 10kΩ resistor per switch is installed

10 programming this program causes the built-in LED on pin 13 to turn on when the switch is pressed living with the lab int whisker1=0; void setup(){ pinMode(7,INPUT); pinMode(13,OUTPUT); } void loop(){ whisker1=digitalRead(7); if(whisker1== HIGH) // whisker1==HIGH if whisker pressed { digitalWrite(13,HIGH); } // turn LED on pin13 on else { digitalWrite(13,LOW); } // turn LED on pin13 off } this is our first time to use if … else control (see next slide)

11 if / else if/else allows greater control over the flow of code than the basic if statement, by allowing multiple tests to be grouped together arduino.cc living with the lab if (x < 500) { // do Thing A } else if (x >= 1000) { // do Thing B } else { // do Thing C } can use an unlimited number of else if blocks... or none, as in the program on the previous slide