Temperature sensors for fridge/freezers

Forums › Gadgets, robotics, home automation, electronics (including wearables) › Temperature sensors for fridge/freezers

nate

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# 165722 18-Feb-2015 13:17

After just about losing a whole fridge worth of stock, I've decided I need to monitor the three fridges and one freezer we have at the cafe.

I don't need anything too fancy, as long as it has an output that I can consume, I can write a program to alert me when they fall outside the norms. Monitoring hardware needs to be WiFi.

Was thinking about these, however, am happy to take suggestions on anything else that people have used.

davidcole

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# 1241677 18-Feb-2015 14:37

What's that thing Ben Gracewood is using. Might be a bit overkill though and prob IOS only (the one and true OS)

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Aredwood

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# 1242046 19-Feb-2015 01:33

What kind of alarm system do you have? As if you have an unused zone input. Connect it up to a thermostat. And configure the panel to contact you if a temperature alarm condition happens.

Also from reading 1 of your blog posts Im guessing you have good coding knowledge? So then the best thing would be to get an Arduino board and a Wifi Shield. That way you will have plenty of inputs so as well as monitoring temps. You can also monitor things like compressor run time, Status of condenser high or low pressure switches, If the power has failed. That way you will know immediately if a refrigeration system failure has occurred. Instead of only finding out when temperatures are out of range.

nate

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# 1242084 19-Feb-2015 08:27

Aredwood: Also from reading 1 of your blog posts Im guessing you have good coding knowledge? So then the best thing would be to get an Arduino board and a Wifi Shield.

Sounds like an awesome idea, I'm assuming I'll also need some sort of temperature sensor to plug into the Arduino?

timmmay

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# 1242092 19-Feb-2015 08:43

Seen this?

Aredwood

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# 1242347 19-Feb-2015 14:39

nate:
Aredwood: Also from reading 1 of your blog posts Im guessing you have good coding knowledge? So then the best thing would be to get an Arduino board and a Wifi Shield.

Sounds like an awesome idea, I'm assuming I'll also need some sort of temperature sensor to plug into the Arduino?

Either get https://nicegear.co.nz/sensors/10k-precision-epoxy-thermistor-3950-ntc/ Which will need 1 analogue input per sensor to work. Or https://nicegear.co.nz/sensors/waterproof-ds18b20-digital-temperature-sensor/ These with the right code can be daisy chained together. So lots of sensors on 1 I/O pin. (and have plans to add more)

I have a system running with 9 of the DS18B20 sensors on just 1 I/O pin. Although if you only need a small number of sensors then use the thermistor sensors instead.

richms

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# 1242410 19-Feb-2015 15:25

Stick with the DS sensors. I got several off ebay that are nicely potted into a piece of stainless that I have in my aquarium to keep an eye on it. I pulled the Pi off it as I wanted to use it somewhere else but there are a crapload of python tutorials on using them on the pi and then hitting up servers with the readings.

The thermistor ones have issues with the odd really out reading from noise when I tried one, like it would be 28, 28, 29, 28, 70, 28 when reading periodically. The DS ones dont seem to do that.

Richard rich.ms

Niel

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# 1242669 19-Feb-2015 22:20

Thermistors will be prone to noise pick-up (as Richms said), but not if you use proper (hardware) filtering and (appropriately) shielded wire. The DS sensors however are just so much better in being calibrated and digital.

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nate

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# 1323362 12-Jun-2015 13:25

I ended up with these from Wireless Sensor Tags. Cost me around NZ$250 for 5 sensors and a base station.

Pretty impressed so far, you can set alarms if the temp goes outside a particular range. Also has a nice mobile app. I'll try and blog it about when I get a chance.

linw

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# 1323410 12-Jun-2015 14:17

Interesting collection of sensors.