Published October 22, 2018 © GPL3+

Raspberry Pi Zero W Scary Halloween Ghost

It has a ultrasonic sensor to detect people presence. When it detects people, it jiggles, makes a random scary sound, and flashes a RGB LED.

IntermediateFull instructions provided10 hours1,191

Raspberry Pi Zero W Scary Halloween Ghost

Things used in this project

Hardware components

Raspberry Pi Zero Wireless

Speaker: 0.25W, 8 ohms

Can use any small speaker, for example, from a old toy

Maxbotix ultrasonic sensor

RGB LED

Servo Module (Generic)

LM386

Story

Start by preparing your SD Card. Flash Raspbian latest release: https://www.raspberrypi.org/downloads/raspbian/ I used Lite version.

Next prepare a PCB for audio. I made mine like this:

Audio low-pass filter and LM386 based amplifier

Next wire everything: Servo, ultrasonic sensor, speaker and RGB LED

The resistors are soldered directly in the wires

After verifying that everything works, it's time to put RaspberryPi and the PCB in a enclosure

Next step is to hang it somewhere and start scaring people: https://www.youtube.com/watch?v=F30RjWSvE70

Code

ghost.py

import RPi.GPIO as GPIO
import time
import sys
import threading
from subprocess import call
import random
import wave
import contextlib

GPIO.setmode(GPIO.BOARD)

servo = 37
sensor = 18
red = 11
green = 13
blue = 15

sensorCount = 0
sound = 0
soundLen = 0.0

GPIO.setup(servo, GPIO.OUT)
GPIO.setup(sensor, GPIO.IN)
GPIO.setup(red, GPIO.OUT)
GPIO.setup(green, GPIO.OUT)
GPIO.setup(blue, GPIO.OUT)

p = GPIO.PWM(servo, 50)
p.start(0)

call(["gpio_alt", "-p", "18", "-f", "5"])


def readSensorDistance():
	pulse_end = 0
	pulse_start = 0
	
	while GPIO.input(sensor) == 0:
		pulse_start = time.time()
	
	while GPIO.input(sensor) == 1:
		pulse_end = time.time() 
	
	return round(((pulse_end - pulse_start) * 6500.0) * 2.54, 2)


def doMotorMovements():
	global soundLen
	elapsedTime = 0.0
	startTime = 0.0
	endTime = 0.0
	while elapsedTime < soundLen:
		startTime = time.time()
		p.ChangeDutyCycle(9.5)
		time.sleep(0.1)
		p.ChangeDutyCycle(12.5)
		time.sleep(0.1)
		endTime = time.time()
		elapsedTime = elapsedTime + (endTime - startTime)
	p.ChangeDutyCycle(12.5)


def playSound(i):
	auxStr = "/home/pi/ghost/" + i + ".wav"
	print auxStr
	call(["aplay", auxStr])


def allColorOff():
	GPIO.output(red, 0)
	GPIO.output(green, 0)
	GPIO.output(blue, 0)
	
	
def doColor():
	global soundLen
	tOn = 0.05
	tOff = 0.05
	elapsedTime = 0.0
	startTime = 0.0
	endTime = 0.0
	while elapsedTime < soundLen:
		startTime = time.time()
		
		GPIO.output(red, 1)
		time.sleep(tOn)
		allColorOff()
		time.sleep(tOff)
		
		GPIO.output(green, 1)
		time.sleep(tOn)
		allColorOff()
		time.sleep(tOff)
		
		GPIO.output(blue, 1)
		time.sleep(tOn)
		allColorOff()
		time.sleep(tOff)
		
		GPIO.output(red, 1)
		GPIO.output(green, 1)
		time.sleep(tOn)
		allColorOff()
		time.sleep(tOff)
		
		GPIO.output(red, 1)
		GPIO.output(blue, 1)
		time.sleep(tOn)
		allColorOff()
		time.sleep(tOff)
		
		GPIO.output(green, 1)
		GPIO.output(blue, 1)
		time.sleep(tOn)
		allColorOff()
		time.sleep(tOff)
		
		GPIO.output(red, 1)
		GPIO.output(green, 1)
		GPIO.output(blue, 1)
		time.sleep(tOn)
		allColorOff()
		
		endTime = time.time()
		elapsedTime = elapsedTime + (endTime - startTime)

	
def getSoundLen(i):
	auxStr = "/home/pi/ghost/" + i + ".wav"
	with contextlib.closing(wave.open(auxStr, 'r')) as f:
		return f.getnframes() / float(f.getframerate())
	

while True:
	try:
		#print readSensorDistance()
		if readSensorDistance() < 130.0:
			sensorCount += 1
		else:
			sensorCount = 0
		#print sensorCount
		if sensorCount >= 3:
			#print "doing scary stuff"
			sound = random.randint(1, 9)
			soundLen = getSoundLen(str(sound))
			threading.Timer(0, doColor).start()
			threading.Timer(0, doMotorMovements).start()
			playSound(str(sound))
	except KeyboardInterrupt:
		GPIO.cleanup()
		sys.exit(0)
	except:
		print sys.exc_info()