Background
During a recent visit to my in-laws, who own and operate a commercial kitchen, I noticed as part of the morning opening procedure the observation and recording of the cool-room and other fridge and freezer temperatures. My curiosity kicked in and asked why the recording of the temperatures to be told it is a council requirement to log temperatures as it is to do with their food handling licence. Whilst this process took only about 5 minutes of a staff members time, my inner geek started to think of more efficient ways to complete such a trivial task.
So it happens, and as Murphy’s Law always does, the next morning was meet with a scramble of staff and a tirade of phone calls to suppliers - during the previous afternoons close down, the cool-room door had inadvertently been left ajar. Not a huge dilemma, until it became evident the now over worked cool-room compressor had failed during the night and with the door ajar, didn’t leave much coolness by 7am.
So with expense of the cool-room repair, the additional staff hours cleaning and disposing of thousands of dollars of now wasted food products and on top of that a limited menu and loss of income due limited food supplies I decided to come up with a system that would hopefully reduce the chance of such losses and provide an automated process of reporting.
Concept
After a discussion with the in-laws, they agreed it would be a huge benefit to them and together we came up with a concept that I think will tick all their needs.
The completed design should include a display module that is capable of displaying both the local Fridge / Freezer and remote sensor data. There should be a indication on the display of current alarms. Automated reports should be emailed which include minimum and maximum daily temperatures and any alarms that occurred during the period.
Alarms! Alarms are to include “Over Temp” and “Under Temp” alarms, with the over temp alarm to be notified by a phone call that requires acknowledgement. Under temp and “Data Loss” alarms, which could indicate a power failure or WiFi outage should be reported by a notification SMS. It was decided not to include the addition of a door alarm but to include an “Above Temp” notification which should accomplish the same task by getting staff to check the fridge / freezer state when activated.
As the location has excellent WiFI coverage, that is the preferred method for relaying data between the remote units and master unit - resulting in being a perfect case for both Raspberry Pi 3 and Raspberry Pi Zero W systems.
Key Hardware
Being that the design contest is primarily based on the Raspberry Pi 3, definitely expect at least one of these to be used. Due to the requirement in the environment I plan to implement, I will be using DS18B20 Thermo Sensors. Being I2C interfaced, I can have more than one sensor to each Raspberry PI. In addition, I plan to also use Raspberry Pi Zero W as remote sensors due to the reduced cost and less hardware requirements.
If I do decide with an onsite backup process, I will need to include a 4G Modem and battery supply (with monitoring). Alternatively, A remote server (such as another Raspberry Pi 3 located externally to provide data backup and data loss notification.
Data will be able to displayed locally on the Raspberry Pi 3, using the 2.4” Screen Hat.
Of course, this is just the theoretically concept so actually hardware may change as the build progresses.
Key Software
I plan of using Raspbian Stretch as the OS. I have a good understanding of the Linux OS so using Raspbian should not prove to relatively easy to get up and running.
On top of the Raspbian, I will try to using packages available using the Raspbian apt repository to allow it easier for other to follow in my steps. Packages I plan on using will include:
lighttpd - a light weight but more than capable web server
php - I am more familiar with php web programming so even though it is probably over kill, it works
sqlite3 - again a lightweight database often using in embedded devices
asterisk - a more than capable VoIP server
Though out the design process, I will try my best to include default settings and show script and configuration changes alas, feel free to point something out if I miss anything. Again, the software may change depending on further investigation and what is more suitable.
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