Tutorial

raspberrypi.org/magpi The Official Raspberry Pi Projects Book 107

WINE SAVER: ROOM TEMPERATURE MONITOR

Language

>C AND BASH

DOWNLOAD:

magpi.cc/2uBzlR4

of the configuration file with sudo nano
/etc/ssmtp/ssmtp.conf.

Wine Room Monitor settings – for gmail

hostname=wineroom
[email protected]
mailhub=smtp.gmail.com:587
FromLineOverride=YES
AuthUser=your gmail name (leave out the @
and stuff after that)
AuthPass=your gmail password (no quotes
needed here)
UseSTARTTLS=YES
UseTLS=YES
AuthUser=LOGIN

Now save the file and exit. As we will run the
monitor program with crontab, we must also change
the /etc/ssmtp/revaliases file or authentication errors
will occur. So, sudo nano /etc/ssmtp/revaliases
and add the following line:

root:[email protected]:smtp.gmail.com:587

Now reboot.

The program
Log back into the Pi. First, create a directory called
wineroom and move into it:

mkdir wineroom
cd wineroom

Download the ds18b20.c file from GitHub
(magpi.cc/2uBzlR4) and customise it for your email
address and your alarm temperature levels. To compile:

gcc ds18b20.c –o ds18b20 –Wall -std=gnu99

Hardware setup
Take the wine bottle cork and cut it to half its length
with a hacksaw. Carefully clamp it and use a ¼′′ bit
to drill a hole lengthwise through the centre of the
cork. Next, push the DS18B20 sensor's stainless steel
through the cork so that it is protruding from the other
end – this is why we cut it in half. Wetting the sensor
may make insertion easier. Now rinse the wine bottle
with hot water and fill it nearly full of water. Wet the
cork and push it carefully into the bottle, then put the
bottle on its side to check for leaks. You may need to
add a bit of silicone to seal around the sensor.
On the stacking header, solder a 4.7 kΩ resistor to
the 3V3 and GPIO 4 pins. Solder the sensor red wire to
3V3; the white wire to GPIO 4; the black wire to GND.
Now plug the header onto the Raspberry Pi (make
sure it’s off!), being careful to get the location of pin 1
(3V3) correct. Boot the Pi up, log in, and test it with:

cd wineroom

sudo ./ds18b20 &

Look at the file in your /home/pi/wineroom directory

called wine.log. There should be one entry. You are way

over the temperature range and should get an email

showing an alarm or alert. This will test whether you’ve

got the email settings correct. If you don’t get an email

in a few minutes, take a look at /etc/ssmtp/ssmtp.conf

again to see whether there are any errors.

Now we create a short script to rename the log file and

add the year and month to the log file name at the end

of every month. Of course, since we run it on the first

of the month, we need last month’s date. Download

logupdate.sh from GitHub, edit it to incorporate your

email address, then make it executable:

chmod +x logupdate.sh

Next, we automate things with crontab by editing

with sudo crontab -e and adding two lines to the

end of the file. The first line runs the code at five

minutes after the hour, every hour of every day, and

the log file renaming happens at four minutes after

midnight on the first of the month.

5 * * * * /home/pi/wineroom/ds18b20

4 0 1 * * /home/pi/wineroom/logupdate.sh

Save the file, then to get the new crontab

entries working:

sudo service cron start

sudo update-rc.d cron defaults

Use some Velcro on the bottom of the Raspberry

Pi Zero W case to attach it to the cooler unit. If there

is no power plug inside the wine cooler, remove a

bit of the sealant around the cooler and run a micro

USB power cable through. Then replace the sealant to

close the system back up, power it up, and let it run!

USE BITVISE

Use Bitvise

instead of

PuTTY (same

developers) to

check on the

temperature at

any time.

Place the wine bottle sensor below the top of the rack

CREATE A

UNIQUE GMAIL

Create a

brand new

Gmail account

just for this

purpose. A

unique Gmail

account for

the wine room

prevents a lot

of spam.