Arduino Meet Raspberry Pi

• 24/9/2016
• 2-minute read

While at the electronics store the other day, I noticed they had motion detectors on sale for only $4. I decided with my latest obsession of electronic tinkering, picking up a OSEEP Passive Infrared Sensor (PIR) Module might be fun.

I guess I should have done a little more reading on the packaging; by the time I was home, I noticed this sensor reported in analog , not digital. This was an issue as the Raspberry Pi only reads digital input.

Lucky for me, I also picked up an Arduino UNO Starter Kit awhile back. I decided this would be a great time to learn more about converting analog signals to digital (one great thing about the UNO is that it has both digital and analog input/output pins).

As an extra, I learned the Nexcon Solar Charger 5000mAh I bough for hiking and camping works great as a Raspberry Pi

power source, in theory I can have a portable motion detector :D

The wiring is rather basic, there is no need for resistors or capacitors, just direct connections.

* Connect motion sensor to the Adruino’s

5v power

and ground. * Connect motion sensor’s signal pin to Analog

A0 pin

on Adruino * Connect Adruino’s Digital

2 pin

to Raspberry Pi’s

GPIO 18

* Connect Andruino’s ground to Raspberry Pi’s Ground Once we are wired up, we can compile and upload the Arduino UNO code using Arduino Studio . Arduino

/*
OSEPP Motion detector analog to digital convertor
https://nessy.info
*/

int analog = A0;
int digital = 2

void setup(){

 // set our digital pin to OUTPUT
 pinMode(digital, OUTPUT);
}

void loop()
{

 // read value from analog pin
 int analog_value = analogRead(analog);

 // send digital signal when motion detected
 if (analog_value > 0) {
   digitalWrite(digital, HIGH);
 } else {
   digitalWrite(digital, LOW);
 }

 delay(100); // slow down the loop just a bit
}

This Arduino code will read analog input from our motion detector, and any time more than 0v is detected it sends a signal to digital pin 2. Raspberry Pi (Python)

import time
from datetime import datetime

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.IN)

def detect():
  while True:
    if GPIO.input(18):
      print '[%s] Movement Detected!' % datetime.now().ctime()
    time.sleep(1)


detect()  # run movement detection

On the Raspberry Pi side we will listen for signal on GPIO pin 18, and print out a little message, and timestamp. From here we can do all sort of things, Happy Hacking!