Temperatures in Pizzeria freezers

General
1

I’m searching for a solution to log temperature values of refrigerators & freezers in restaurants.

I’d like to ask for any suggestions, what:

  • devices,
  • nodes
    work fine with node-red ?

The problems with this request are:

  1. Temp value range. (Most devices can not handle -40 °C)

  2. Freezers are shielding too well
    (so maybe the devices should go outside, but the sensor inside with thin/flat cable?)

  3. The owners are running Win7 / Win10 systems.

PS/Edit:

... there are other considerations that can complicate the job. Here more here...

2

Hello Pizza

I solved a similar problem at a radio station after 50 kg of bacon went off after a circuit breaker tripped on a long weekend

I used a 1 wire solution using SMNP

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we just made a small hole in the seal and had 1 sensor per freezer

as far as an OS.. you could put a cheap NUC running Linux or PI there running node-red

Some would disagree but node-red runs more stable under linux

Hope this helps

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3

I believe the ds18b20 sensors can work down to -55C.

They are easy to set up as it has a 1-wire interface , and the stainless steel probe versions are tough and practically hermetically sealed.

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4

Can you please give a bit more info about it?

  • what’s that black device exactly on the picture? (manufacturer + model)
  • what type of 1-Wire sensors did you use?
  • which node-red node are you using? (this one?)
5

This is the one I actually used but they are basically all the same

This is all the sensors you can get

I used the standard SNMP node.. you can also get it to send email, send custom TCP data

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6

That is correct. And they are widely and cheaply available in a standard waterproof package. Also widely supported by software and firmware.

Not sure about more stable but certainly easier to set up and maintain.

Of course, if you already have a server you can use and are happy to run MQTT on it and if it has reliable Wi-Fi, I'd say use a cheap ESP32 to connect the sensor to and output to MQTT.

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7

The WebRelay module looks quite expensive >$200, so unless you need PoE, Celluar and Relay Output functionality - you might be able to implement a cheaper DIY solution like this...

The ESP32 supports 1-wire using Micro-Python or Ardunio.

The DS18B20 devices can be daisy-chained together as they have a 64-bit unique serial code.

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8

Though obviously depends on the customer. They might prefer the more expensive, commercial model as an all-in-one solution.

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9

Agreed.
As an avid DIY enthusiast, the list price of the WebRelay put me off.

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10

Thank You all, very much for all the infos! :slight_smile:

A few additional thoughts:

  • Yes, cheap prices would be nice, because in my country nobody would pay $200+ for a device.
  • But sadly I do not have much time and all the equipments to solder and box everything together 10-20-100 times.
  • Also most of those 5-10+ fridges are far away from each other, so it would be hard to daisy chain all of them together!
  • In most cases even wiring + drilling wholes is complicated for most of the restaurant owners, and they will not pay me enough to travel 50-800Km to do it for them.

(Not to mention they are open every each day, from ca 07AM - to 23:30PM … so any drilling + wiring is impossible in that time while people are cooking food there!)

So I’m looking for some kind of “golden middle way”.

11

M5 Stack have pre-build ESP32 devices that might fit the bill. Wiring in a DS18B20 would be simple.

While access to MQTT would be good, you could instead just create a simple Internet-facing API (Or better still a local one using existing on-prem servers) that the unit could call if temperatures were outside the correct range.

They have a range of packaged controllers some with small screens in case you wanted people to be able see the temperature locally as well.

Even something like the Atom Matrix could be used to give a quick visual indication of temperature as well as sending alerts wirelessly:

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12

I have found on this forum so far only one possibility:

Here are 433MHz wireless temp readers.
This one is $20 and supports -40°C

But I haven’t found any USB dongle yet to receive the data. Also it seems to work on Linux only.

one more consideration:

it would be nice (and logical) for the gateways to store those values for a while, if the PC/Tablet is offline or there is something wrong with the internet.
15sec reading = 24 * 60 * 4 * (4+8) byte = 70 KiB / sensor / day

13

Cool !!! This could be it :+1:

Sadly a “simple warning system” is not enough. Logging of data is a must to comply National Food Chain Safety Office.

14

I'd probably go with something that is off the shelf and easier to integrate - something like this ZigBee device: Sonoff Waterproof Zigbee LCD Smart Thermometer (Probe Version)

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15

It looks like with all of those the sensor module communicates wirelessly from inside the freezer?

Maybe their batteries will still work down to -40° but in any case, don't the freezer cabinets block the signal?

  • How modern are these freezers? Do they already offer external temperature reporting to comply with regulations?

  • Can you rely on there being a working wireless network at each location 24/7?

  • Can you rely on a power supply such as USB being available nearby?

It's tempting to imagine a DIY solution with ds18b20 sensors and ESP32 or Raspberry Pi but neither the inside of a freezer nor a restaurant kitchen are friendly environments for electronic components. How to adequately seal everything?

16

Thank you very much for the link!

This device seems to comply every standard I wished for.
The Zigbee dongle is cheap too, and Windows compatible.
Also like the idea of an iHost or Zigbee Bridge.

The only thing I haven't found yet, is the "repeater device", so mesh can network work on wide areas too. Or are those thermometers also repeaters?

Starting to dig into Zegbee now...

17

Ah, you didn't say Zigbee would be acceptable. Sonoff was the first place I looked but I discounted their Zigbee range.

You will probably still need access to an MQTT server of course.

18

Off the self and with multiple communication protocols, you could look at shelly devices,

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19

If you are going to use Zigbee, then this would be one of the best solutions to bridge to MQTT.

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20

I would check if the freezer has exposed controller + temp sensor already. If it has, then hijack the controller or sensor signals with another controller and some wiring.