- Use Case
I'm in the process of closing on a small cabin/cottage up in NH. My use case/requirement is to build inexpensive system to monitor the site/structure when I'm out of town. Of note, the system must be:
- Inexpensive ($15-25) and make use of as many parts on hand as possible
- Capture video and other telemetry (temp)
- Able to push data remote, as in beyond the local network
- Operate off cell data or WiFi (understanding that cell data will be difficult if pushing video)
- Relatively easy to configure
Engineering Steps
After some initial tinkering and prototyping, I figured I'd adopt the following approach:
Let's Build
1. Build prototype and determine board type.
First step is always research. I spent hours considering board types (Arduino, Particle, Raspberry Pi) since I have examples of all of these. I eliminated Arduino early in the game as that solution required additional boards for communications, namely WiFi. My Photon Particle boards came in second. They are about 5+ years old and required some work but they might make due for the telemetry portion of the project. They do not, however, have sufficient processing power to handle video. This left me with the Raspberry Pi. I have several running around the house: Build-A-Pi for Winlink, another for tracking radiosondes launched out of IAD, and another running 24/7 as a FightAware PiAware device.Now, I looked at potentially repurposing the radiosondes receiver since that use is periodic. [Note, I wanted to use this as a project to not only track sondes, but estimate path and retrieve the sondes that might land on terra firma. Still haven't been able to get to this.] There is a Raspberry Pi image specifically devoted to home automation. I burned the Home Assistant image several times but could not get it running.
Instead I bought two Raspberry Pi Zero 2W's. These were, by far, the easiest to configure with the most avail code examples that I could borrow. Plus, the form factor was right on the money.
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| Raspberry Pi Zero 2W |
2. Build video capture app on one board. Test.
I reviewed and tested several applications and images. The most promising, ContaCam seemed only to work with Windows and/or full Linux images.I then tested Motion using several platforms. Motion is installed with the latest RPi images, so the codebase is well adopted and stable. Since I like to operate my devices headless (that is, without installing a monitor and keyboard, but instead remoting into the device), I configured this capability first. Here's a quick tutorial. I then installed/configured Motion NOT as in image, but the program itself (I never could get the slimed down MotionEye OS image to install and work correctly.)
After installing and configuring the motion.conf files, I plugged in an old USB webcam and was off to the races.
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| Camera Livestream |
Once everything was running to my satisfaction, I turned on port forwarding on my router so that I could see the livestream from anywhere with a connection.
3. Build telemetry (temp, humidity) using DHT22 (b/c I have several)
My next requirement was to build something that would allow remote environmental monitoring. I have built several weather stations for the backyard, but I could never solve the power problem (operate off a battery, recharge with a solar cell. Once the temps dropped below 40F, forget about it.) Those stations were based on the DHT11 and its DHT22 cousin sensor. Only three terminals used: +3v3, GND, and Data. Data terminal uses a 10k pull up resistor. |
| DHT11, abt $5 |
In the past, I've used Thingspeak as my data repository. While several IOT repositories have gone by the wayside in the 5-6 yrs since I've messed with this stuff, Thingspeak/Mathlab is still in the business.
After some research, I settled on using the Thingspeak library.
Some helpful tools:
- GPIO Pinout Guide: https://pinout.xyz/pinout/3v3_power
- DHT22: https://learn.adafruit.com/dht-humidity-sensing-on-raspberry-pi-with-gdocs-logging/python-setup
- Thingspeak Integration: https://github.com/fmandal/dht22
I sifted through enormous amounts of complex code and finally settled on my adoption of an IOT Starters version:
import thingspeak
import time
import Adafruit_DHT
channel_id = 1577517 # put here the ID of the channel you created before
write_key = 'LWX0MK4IX0RLBC94' # update the "WRITE KEY"
pin = 3
sensor = Adafruit_DHT.DHT22
def measure(channel):
try:
humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)
tempF=(temperature * 1.8) + 32
if humidity is not None and temperature is not None:
print('Temperature = {0:0.1f}*C Humidity = {1:0.1f}%'.format(tempF, humidity))
else:
print('Did not receive any reading from sensor. Please check!')
# update the value
response = channel.update({'field1': tempF, 'field2': humidity})
except:
print("connection failure")
if __name__ == "__main__":
channel = thingspeak.Channel(id=channel_id, api_key=write_key)
while True:
measure(channel)
#free account has a limitation of 10 min (60 sec * 10 min) between the updates
time.sleep(600)
4. Combine both apps on a single board
Since the telemetry development was freshest in my head, I decided to use the working Motion program and add telemetry on a single card. I then backed up the card as an image in case of crisis.
The next very important step was to add some type of auto-starting. If the power blipped or went out, I would have no way remotely to restart programs. I tried several code samples, but settled on using .desktop files.
Here are the basic instructions from https://learn.sparkfun.com/tutorials/how-to-run-a-raspberry-pi-program-on-startup/all ):
Create a .desktop File
You do not need root-level access to modify your profile's (user's) autostart and .desktop files. In fact, it is recommended that you do not use sudo, as you may affect the permissions of the file (e.g. the file would be owned by root) and make them unable to be executed by autostart (which has user-level permissions).
Open a terminal, and execute the following commands to create an autostart directory (if one does not already exist) and edit a .desktop file for our clock example:
mkdir /home/pi/.config/autostart
nano /home/pi/.config/autostart/clock.desktop
Copy in the following text into the clock.desktop ile. Feel free to change the Name and Exec variables to your particular application.
motion.desktop:
[Desktop Entry]
Type=Application
Name=Motion
Exec=sudo /bin/motion start
thingspeak.desktop:
[Desktop Entry]
Type=Application
Name=Thingspeak
Exec=/usr/bin/python3 /home/pi/DHT22_Thingspeak.py
5. Add web hooks for iot triggers
TBD
6. Harden system/prep for deployment
TBD
