RaspPiTempFan

Raspberry Pi Temperature control of a wall fan to control temperature of garage

OVERVIEW

This project uses a raspberry Pi to check the temperature inside a garage and ambient outside temperature and turn on a wall fan that will blow hot air out of the garage and suck in cool air to cool the garage.

By having a temperature sensor outside, the program running on the raspberry pi will decide whether venting the garage makes sense. IE, if it's hotter outside than inside, then it doesn't make sense to vent the garage.

PARTS

RaspberryPi or Similar (TBD)

RaspberryPi

3.3Vdc Input 120/10A Output Relay Solid State Relay

Icstation 3V 1 Channel Relay Power Switch Module with Optocoupler

DataSheet

How much current?? The gpio pin is connected to the input of an optical coupler on the relay board. Mine drew 0.15mA from the GPIO pin and 78mA of power from the 3.3v power rail in the on state.

How to setup? My working configuration is:
gnd = gnd pin from pi + external 3.3vdc -
Signal = output pin from pi
VCC = external 3.3vdc +
Jumpers = on

Temperature Sensor DS18B20

Aideepen 5pcs DS18B20 Waterproof Temperature Sensor Digital Thermal Stainless Steel Tube Probe 1 Meter

Output lead:
Red- VCC
Yellow- DATA
Black-GND

HiLetgo DHT11 Temperature and Humidity Sensor Module (Not Implemented)

HiLetgo 5pcs DHT11 Temperature and Humidity Sensor Module Unfortunately, this sensor has not been added to the c-code and is slated for a future release. The impetus to include this is to monitor humidity in the garage. The real need is to monitor temperature, which is being done with the DS18B20, so this is an add-on slated for future implementation. See the RefLinks.md for DHT11 info.

10 Inch Shutter Exhaust Fan

Iliving 10 Inch Variable Speed Shutter Exhaust Fan, Wall-Mounted

KB Electronics Variable Speed AC Motor Control

KB Electronics 8811012 Solid State Variable Speed AC Electric Motor Control, 5.0 Max amp, 115V, # K177-1005

RASPBERRY PI SETUP

Raspberry Pi

Prerequisite is to have a running Raspberry Pi with Stretch or stretch-lite installed. I used a Raspberry Pi 3 Model B v1.2.

uname -a Linux autopi 4.14.34-v7+ #1110 SMP Mon Apr 16 15:18:51 BST 2018 armv7l GNU/Linux

SETUP SSH

Not covered in detail, but you might want to setup SSH and a remote terminal to talk 'headless' to the raspberry pi. I do this so that I don't need a separate 'workstation' with a monitor, keyboard, and mouse connected directly to the raspberry pi. This way, I can setup the raspberry pi, plug it in and connect to it remotely from my latptop where I usually do most of my computer work.

The internet has many examples - google how to setup SSH. If using windows, install PUTTY. Also, WinSCP is a useful Windows install that allows you to transfer files to and from your remote raspberry pi or any linux OS computer for that matter.

Lastly, to find your RaspPi on your network, a nice tool is Angry IP Scanner that allows you to scan your network (ie 192.168.0.0 to 192.168.0.255) to find any computers connected to the network.

SETUP STATIC IP ADDRESS

I never used to setup static IP Addresses on linux boxes, but it makes sense so that you don't have to run Angry IP Scanner to find the IP address or login in directly to the computer to find the IP Address. The latter is problematic because because it means I need to take the RaspPi to a monitor, keyboard, and mouse and boot it. Too much futzing around...

Here are 2 resources for setting up static IP Addresses:
http://www.circuitbasics.com/how-to-set-up-a-static-ip-on-the-raspberry-pi/
https://www.modmypi.com/blog/how-to-give-your-raspberry-pi-a-static-ip-address-update

PRO TIP - Create a file backup before modifying important files

Example below referenced from here.
sudo cp -n /etc/dhcpcd.conf /etc/dhcpcd.conf.orig

If for some reason you want to revert to original settings, just run the command below in terminal:
sudo mv /etc/dhcpcd.conf.orig /etc/dhcpcd.conf

Static IP Address Setup Tips/Notes

The example at circuit basics shows how to find your default gateway IP with:
route -ne

And, the IP addresses of your domain name with:
cat /etc/resolv.conf

Then, modify your dhcpcd.conf (make backup as shown above)
sudo nano /etc/dhcpcd.conf

Then, reboot:
sudo reboot

Use Putty to ssh into the new static IP address. I made sure to setup my wifi (wlan0) ip address to a static address so I could work on my rasppi anywhere in the house where it was plugged in and could reach the wifi.

TEMPERATURE TEST AND SETUP FOR DS18B20

Started off by following this tutorial. I checked the data sheet for the DS18B20 (References Folder) and it can accept 3.3vdc or 5vdc input.

Wire sensor to the Rasperry Pi by adapting from Blinkio

Setup of the one-wire interface

There are a few tutorials easily found on the web to interface a Raspberry Pi to the DS18B20 temperature sensor. But, usually they simply tell you how to connect, but may or (usually) may not tell you what you're doing behind the scenes. A little googling found a few resources, of which have been cut and paste into text files and saved in the References Folder:
https://www.kernel.org/doc/Documentation/w1/w1.generic
https://jumpnowtek.com/rpi/Using-DS18B20-1-wire-Temp-Sensors-with-the-Raspberry-Pi.html

Using this example, here are the following steps:

Let's backup config.txt

sudo cp -n /boot/config.txt /boot/config.txt.orig

If for some reason you want to revert to original settings, just run the command below in terminal:
sudo mv /boot/config.txt.orig /boot/config.txt

Update /boot/config.txt:

Update the config.txt file by opening the file:
sudo nano /boot/config.txt

Add the following line:

dtoverlay=w1-gpio,gpiopin=26
The gpiopin changes the dtoverlay from default gpio 4 to gpio 26. I'm using gpio 26 because gpio 4, gpio 5, and gpio 6 are used from blinkio. If you want to use the default gpio pin 4, do not use the gpiopin=26 and only add the following line:
dtoverlay=w1-gpio

Reboot

sudo reboot

Check for Connected Devices

cd /sys/bus/w1/devices
ls
Response: 28-01143c62f7aa 28-01143fb265aa 28-01143fc657aa w1_bus_master1

Get the Sensor ID

Each sensor has a unique ID beginning with 28-00000xxxxxxx. Check the temperature by issuing the following commands:
cd 28-00000xxxxxxx
ls
cat w1_slave

The Output looks like...

(Display output here...)

LET'S CODE

In order to expedite code, I borrowed the base code from https://github.com/floppydisk525/blinkio. I already had a breadboard setup for an input, output LED, and heart beat timer. Seems logical to use those items as a precursor for this project. Ultimatley, I would like to have an input button to act as an override from the Raspberry Pi control and turn it on manually.

I renamed the code to tempio.c (from blinkio.c) and placed it in the cprog folder of this project. Also, I updated the header text to indicate the change in the tempio.c file.

Note that GPIO is setup the following way:
GPIO 4 - pushbutton input
GPIO 5 - Output LED triggered by Pushbutton
GPIO 6 - HeartBeat

Let's start by customizing the new tempio.c program for temperature setup. Before we do that, we need to be able to compile and run the program.

Compile and Run c program tempio.c

Compile the c program tempio.c:
gcc -o tempio -l rt tempio.c -l bcm2835

Run the c program:
sudo ./tempio

Program Additions for Temperature

We need to add a few functions (c terminology for a subroutine or c# method) for reading the temperature and are utilizing code from Brad's c-program, and saved that program for reference in the file Temp1sensor.c in the cprog/Ref folder.
The additions include:
Global Variables for Reading Temperature
DS18Setup () Method to setup 1-wire devices
DS18ReadCheckTime () Method that checks the temperature in a pre-defined interval in seconds DS18ReadTemp () Read the 1-wire DS18B20 device.

The main program calls the DS18ReadCheckTime () method and when the desired number of seconds elapse, the method calls DS18ReadTemp() method to actually read the one-wire device.

Does anything go easily in programming? Strings, pointers, and 2d Array's in c code. Also, clang (cl) vs. gcc...

I now see why python is the scripting quick programming choice! Ever try to work with an array of strings in c code? Yeah, well, strings and string arrays don't exist like they would in C#. What you need is a 2d char array. Sounds easy, but try to send that 2d char array to a function. Further complicating the fun is that the microsft c compiler clang would not compile a program I got to compile in gcc on the raspberry pi. Not liking compiler warnings in general and being the perfectionist freak that I am, I wanted my code to compile on both clang and gcc without warnings. It was a small task, but I needed to learn how to declare a 2d char array and send it to functions. One thing to point out is that a a char array, which is just a string in C#, can be setup and used with a pointer. But, if you haven't used pointers before, it can get confusing quickly. The idea isn't that confusing but the syntax can be tricky to figure out the first time using it. Two resources helped with this issue:

A function that creates and returns a 2d array:
https://www.quora.com/How-can-I-declare-a-2-dimensional-array-of-char-in-C
A working program that compiles in clang or gcc can be found in \cprog\Ref\ArrayTest called arraytest2.c. Download it, compile, and run it...

Also, the 1988 c Programming K&R 'bible':
https://www.dipmat.univpm.it/~demeio/public/the_c_programming_language_2.pdf
I just started reading sections that I needed on pointers, malloc, and other topics and this aided greatly in understanding. I will admit I'm still weak on pointer syntax, but considering I don't live this everyday, I'm very happy with getting my code to work. Maybe python for my next program...

RELEASES

Release v0.01 tests the addition of the read temperature code and the second timer method, but doesn't actually read the temperature.
Release v0.02 adds the reading of temperature for qty 1 1-wire device.
Release v0.3.0 adds multiple 1-wire devices. Note that button and heartbeat functionality are TOO SLOW. Need pthread.

FUTURE RELEASE STRATEGY

Release v0.3.1 to add pthread to improve button and heartbeat functionality. Release v0.3.2 to add offsets to DS18B20 temp readings (ie single point calibration).
Release v0.3.3 to add storing values in sqllite DB.
Release v0.4.0 to add simple/basic fan control based on outside and garage temperature Release v0.x pthread to remove lagginess from push button (This is nice to have for this project). See RefLinks.md file for web links to example.
Release v0.x DHT11 sensor connectivity. Currently not implemented.
Release v0.x PID control.

RESOURCES