Lesson 7 Tilt-Switch Module

Introduction

The tilt-switch module (as shown below) used here is a ball one with a metal ball inside. It is used to detect inclinations of a small angle.

Components

– 1 * Raspberry Pi

– 1 * Breadboard

– 1 * Network cable (or USB wireless network adapter)

– 1 * Dual-color LED module

– 1 * Tilt-switch module

– 2 * 3-Pin anti-reverse cable

Experimental Principle

The principle is very simple. The ball in the tilt-switch changes with different angle of inclination to trigger the circuit. When the ball runs from one end to the other end due to shaking caused by external force, the tilt switch will conduct and the LED will flash red, otherwise it will break and the LED will flash green.

The schematic diagram:

Experimental Procedures

Step 1: Build the circuit

Raspberry Pi	Tilt Switch Module
GPIO0	SIG
5V	VCC
GND	GND

Raspberry Pi	Dual-Color LED Module
GPIO1	R
GND	GND
GPIO2	G

For C language users:

Step 2: Change directory

 cd /home/pi/SunFounder_SensorKit_for_RPi2/C/07_tilt_switch/

Step 3: Compile

gcc tilt_switch.c –lwiringPi

Step 4: Run

sudo ./a.out

For Python users:

Step 2: Change directory

 cd /home/pi/SunFounder_SensorKit_for_RPi2/Python/

Step 3: Run

sudo python 07_tilt_switch.py

Place the tilt switch module horizontally, and the LED will flash green. If you tilt it, “Tilt!” will be printed on the screen and the LED will change to red. Place it horizontally again, and the LED will flash green again.

C Code

#include <wiringPi.h>
#include <stdio.h>

#define TiltPin		0
#define Gpin		1
#define Rpin		2

void LED(char* color)
{
	pinMode(Gpin, OUTPUT);
	pinMode(Rpin, OUTPUT);
	if (color == "RED")
	{
		digitalWrite(Rpin, HIGH);
		digitalWrite(Gpin, LOW);
	}
	else if (color == "GREEN")
	{
		digitalWrite(Rpin, LOW);
		digitalWrite(Gpin, HIGH);
	}
	else
		printf("LED Error");
}

int main(void)
{
	if(wiringPiSetup() == -1){ //when initialize wiring failed,print messageto screen
		printf("setup wiringPi failed !");
		return 1; 
	}

	pinMode(TiltPin, INPUT);
	LED("GREEN");
	
	while(1){
		if(0 == digitalRead(TiltPin)){
			delay(10);
			if(0 == digitalRead(TiltPin)){
				LED("RED");
				printf("Tilt!\n");
			}
		}
		else if(1 == digitalRead(TiltPin)){
			delay(10);
			if(1 == digitalRead(TiltPin)){
				while(!digitalRead(TiltPin));
				LED("GREEN");
			}
		}
	}
	return 0;
}

 Python Code

#!/usr/bin/env python
import RPi.GPIO as GPIO

TiltPin = 11
Gpin   = 12
Rpin   = 13

def setup():
	GPIO.setmode(GPIO.BOARD)       # Numbers GPIOs by physical location
	GPIO.setup(Gpin, GPIO.OUT)     # Set Green Led Pin mode to output
	GPIO.setup(Rpin, GPIO.OUT)     # Set Red Led Pin mode to output
	GPIO.setup(TiltPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)    # Set BtnPin's mode is input, and pull up to high level(3.3V)
	GPIO.add_event_detect(TiltPin, GPIO.BOTH, callback=detect, bouncetime=200)

def Led(x):
	if x == 0:
		GPIO.output(Rpin, 1)
		GPIO.output(Gpin, 0)
	if x == 1:
		GPIO.output(Rpin, 0)
		GPIO.output(Gpin, 1)

def Print(x):
	if x == 0:
		print '    *************'
		print '    *   Tilt!   *'
		print '    *************'

def detect(chn):
	Led(GPIO.input(TiltPin))
	Print(GPIO.input(TiltPin))

def loop():
	while True:
		pass

def destroy():
	GPIO.output(Gpin, GPIO.HIGH)       # Green led off
	GPIO.output(Rpin, GPIO.HIGH)       # Red led off
	GPIO.cleanup()                     # Release resource

if __name__ == '__main__':     # Program start from here
	setup()
	try:
		loop()
	except KeyboardInterrupt:  # When 'Ctrl+C' is pressed, the child program destroy() will be  executed.
		destroy()