I’ve been blogging about my experience in Road Test reviewing the Ultimate Raspberry Pi Bundle. As a part of this Road Test I’m creating a Fridge/Freezer Temperature Alarm system for our local food shelf, Channel 1. You can see where this Road Test started for me here
Last Christmas vacation, I volunteered for a local food shelf called Channel One. I was chatting with the warehouse manager and he mentioned that their large freezer and cooler rooms are protected by commercial monitoring systems, but he’d really like a temperature monitor for their walk-in display-case cooler and freezer. The food shelf is closed from Friday Noon until Monday at 8am, they’ve had several cases where the unit has blown a fuse and food has been ruined. My goal was to use the Ultimate Raspberry Pi Bundle to build a low cost temperature monitoring system that can send free text messages when the temperature in the fridge or freezer is outside of the acceptable range.
Monitor the temperature of the Freezer and the Fridge Unit – the valid temperature target is 33F in the fridge unit, and -10F in the freezer unit. However, during business hours, the doors are opened by customers and stocking personnel, so the the fridge could possibly fluctuate to 60F. So allow for a wider temperature range during Business Hours vs Off Hours.
Audible temp range alarm. Make some noise when the temperature is out of range.
Snooze Alarm – If the temperature range is out of whack, support a button that stops the noise.
Text message – when the temperature is out of range, send a text message to someone who can either fix the problem, or move the food.
LCD Temperature display -make the unit wall mountable, we’ll mount it outside of the cold of the fridge/freezer unit but the temperature will be visible to staff.
Adafruit RGB Positive 16×2 LCD+Keypad Kit for Raspberry Pi: This new Adafruit Pi Plate makes it easy to use an RGB 16×2 Character LCD. We really like the RGB Character LCDs we stock in the shop. (For RGB we have RGB negative and RGB positive.) Unfortunately, these LCDs do require quite a few digital pins, 6 to control the LCD and then another 3 to control the RGB backlight for a total of 9 pins. That’s nearly all the GPIO available on a Pi! Read more.
Waterproof DS18B20 Digital temperature sensor + extras: This is a pre-wired and waterproofed version of the DS18B20 sensor. Handy for when you need to measure something far away, or in wet conditions. While the sensor is good up to 125°C the cable is jacketed in PVC so we suggest keeping it under 100°C. Because they are digital, you don’t get any signal degradation even over long distances! These 1-wire digital temperature sensors are fairly precise (±0.5°C over much of the range) and can give up to 12 bits of precision from the onboard digital-to-analog converter. They work great with any microcontroller using a single digital pin, and you can even connect multiple ones to the same pin, each one has a unique 64-bit ID burned in at the factory to differentiate them. Usable with 3.0-5.0V systems.
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Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.