Quick and dirty software
The Python code in the Code 1 block below will monitor pin 16 of the Raspberry Pi and print “Motion Detected” to the screen when the key-fob button is pressed. After the motion detector reset time limit has been exceeded it will print “Motion detector reset” to the screen.
|
#!/usr/bin/env python “”” Wireless Motion Sensor: Quick and dirty keyfob For the Raspberry Pi “””
import RPi.GPIO as GPIO from time import sleep
#main program def main(): GPIO.setmode(GPIO.BOARD) GPIO.setup(16, GPIO.IN) #RF Remote Receiver
motion = False
while True: if GPIO.input(16) == False: #RF key-fob key pressed if motion == False: motion = True print “Motion Detected” else: if motion == True: print “Motion detector reset” motion = False
sleep(.3)
if __name__ == “__main__”: main() |
Code 1 – Quick and dirty wireless motion sensor Python code for Raspberry Pi
Wireless option 2 – Professional
This option is based on CISECO XRF module (figure 7) which has the Texas Instruments CC1110 at its core ($1.50) but CISECO have packaged it on a user friendly 20 pin module with all the software required to send and receive RF signals. CISECO (www.ciseco.co.uk) also have a range of wireless sensors, breakout boards and a Raspberry Pi Inventors Kit making interfacing wireless sensors a trivial task. Both the transmitter and the receiver are the same module except with different software loaded onto them. CISECO provide all the software, however loading the software does require moderate Linux operating system knowledge.
Figure 7 – XRF wireless RF radio UART RS232 serial data module
Professional
Figure 8 is the circuit diagram for the professional wireless motion sensor transmitter unit. As with the quick and dirty option this uses the NPN222a transistor as the electronic switch and the PIR sensor is powered by 2 AA batteries connected in series. The XRF is also powered by the 3V battery pack with the positive 3 volts connected to pin 1 and ground to pin 9. The XRF module needs the button firmware loaded. We’ll be using “type 8” of the button personality which sends a BUTTONON and BUTTONOF message when the PIR switches the circuit on and off. More details on this personality and how to configure the XRF can be found at:
· http://openmicros.org/index.php/articles/84-xrf-basics/215-xrf-firmware-upload-with-a-raspberry-pi
· https://github.com/CisecoPlc/XRF-Firmware-downloads
Figure 8 – The professional wireless motion sensor transmitter
Figure 9 is the circuitry for the receiver that connects to the Raspberry Pi. The XRF pins 1 and 10 go to +3V and Ground respectively on the Raspberry Pi. XRF pins 2 and 3 go to pin 10 and 12 of the Raspberry Pi respectively. Pins 10 and 12 on the Raspberry Pi are the transmit and receive serial interface pins.
Figure 9 – Professional wireless motion sensor receiver
Professional wireless motion sensor software
The Python code in the Code 2 block below will monitor the serial port of the Raspberry Pi and print “Motion Detected” to the screen when motion is detected. After the motion detector reset time limit has been exceeded it will print “Motion detector reset” to the screen.
|
#!/usr/bin/env python “”” Wireless Motion Sensor: Professional using XRF For the Raspberry Pi “””
import serial from time import sleep import sys
defmain(): # loop until the serial buffer is empty currvalue=” # declare to variables, holding the com port we wish to talk to and the speed port = ‘/dev/ttyAMA0’ baud = 9600
# open a serial connection using the variables above ser = serial.Serial(port=port, baudrate=baud)
# wait for a moment before doing anything else sleep(0.2)
whileTrue: while ser.inWaiting(): # read a single character char = ser.read()
# check we have the start of a LLAP message if char == ‘a’: # start building the full llap message by adding the ‘a’ we have llapMsg = ‘a’
# read in the next 11 characters form the serial buffer # into the llap message llapMsg += ser.read(11)
# now we split the llap message apart into devID and data devID = llapMsg[1:3] data = llapMsg[3:]
if data.startswith(‘BUTTONAON’): print“Motion detected”
if data.startswith(‘BUTTONAOF’): print“Motion detector reset”
sleep(0.2)
if __name__ == “__main__”: main()
|
Code 1 – Professional wireless motion sensor Python code for Raspberry Pi
Over to you
So now that you have built your wireless motion sensor you will want to put it into service and notify you, or sound an alarm when motion is detected. At PrivateEyePi we have many more tutorials like this that show you how to build your own alarm system (projects.privateeyepi.com).
For project parts used in this tutorial please visit www.privateeyepi.com/store
Comments are closed.