Temperature Monitoring Hardware

I currently us Siemens Logo to measure some temperatures at pipework; I now want addtional points where I measure temperature that are remote from the Logo. I know I can do it with the Logo; but if there some cheapish devices that are node red compatible, but can be used to measure temp. Multiple readings from one device is fine but I have multiple locations I want to read temps. Ethernet is fine......wireless fine also.

Any ideas?
Regards,
Ant

A battery powered ESP8266 (Wemos D1 Mini) with a 1-wire DS18B20 temperature sensor would give you a cheap solution. ESP Easy as software or Tasmota. Data over MQTT to Node red.

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Just off the top of my head if it's only for temperature... you could use a DS18B20 and a Wemos.

The Wemos D1 Mini is an 8-bit WiFi-enabled microcontroller that costs less than ÂŁ2.
You could use ESP-Easy or Tasmota firmware.
I'm in the UK so I'm quoting UK suppliers.

You can purchase these inexpensive items from China if you are not in a hurry.

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Would I need anything else than a Wemos D1 mini and the DS18B20? Are they battery powered and 1 per temp monitor? So if I need 5 temps at on location I would need 5 x the WEMOS? Any suggested suppliers?

Cheers,
Ant

The Wemos D1 Mini runs off of 5V. It has an onboard 3V3 regulator to power the ESP8266 chip.
Like the Raspberry Pi, the I/O pins are 3V3 (so don't think about connecting 5V logic to them) !!!
Depending on what I'm doing I run my Wemos modules off of 5V mains adapters, 5V power blocks or a Li-Ion rechargeable battery in my solar powered weather station.

Although I've not tried it, you should be able to use a number of DS18B20s with a single Wemos.

Regarding the question about suppliers... where are you located in the world??

Based in the UK. I don't want to buy the wrong thing, to get going. Looks a really interesting little module, perfect for what I'm after.

Thanks,
Ant

I can't see them on Amazon at the moment. You can probably find them on e-bay.

If your're not in a hurry (two-weeks delivery) then you can get them for ÂŁ1.52 from Ali-Express.
Get the D1 Mini v3 version (if you can).

Ali-Express also stock the DS18B20 sensor for 78p !!!!

I've only used ESP-Easy firmware which has all the device-drivers built-in, so it is very easy to use.
Other people on the forum have used Tasmota (which I think is just as easy to use). Depending on your experience, you could also use Arduino code or C++

While they are great because they have built-in USB power supplies, you cannot compare D1-mini's to a Siemens industrial sensor.

In particular, be very wary of fake devices that may fail rapidly (often because of cheap FLASH memory that will only take a few writes before failing).

Having said that, like many on the forum, I run a few of these around the house and they are mostly pretty stable. I think I've only had one actually fail completely in a few years of use.

If you need really low-power for battery life though, look elsewhere because the electronics in the power supply isn't tuned for really low-power use. You can tweak the ESP settings but it isn't absolutely ideal.

To weigh in, I've used the ds18's and like them, there is also the dht 11 and dht 22 which I like, although there are different opinions on the dht sensor, there are numerous other sensors to be sure but on the ones I've mentioned, I've used dozens of them over the years, easy to program, quite reliable if designed properly and reasonably accurate

As Julian said... the Wemos is not really suited to battery operation as it takes about 140mA when it is transmitting via the WiFi. However you can put the device into DeepSleep which reduces the current consumption dramatically. So for example, you could take a temperature reading once every 15-minutes or so, so the battery should last a lot longer.

Please don't use the DHT sensors, they really are rubbish and very much out of date. Not only are they not terribly accurate to begin with, they drift off over time. Best to use one of the newer generation sensors from Bosch or Sensiron. They are now just as cheap anyway.

Either way, the DS18's are better for just temperature sensing and generally come built into a waterproof housing.

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Dave, I had one of these cheap DS18B20 waterproof probes as an outside temperature sensor. It didn't last a year. Last week it failed completely.

I stripped away the shrink tubing and pulled the sensor out. It was wet and one of the legs on the DS18B20 was corroded through. The potting compound (silicone) was really badly done too.

I would recommend paying a bit more if you need a reliable waterproof sensor.

For measuring pipes it might be easier to used ordinary DS18B20's attached to the pipe with a cable tie and a bit of thermal compound to ensure good readings.

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Yes, sounds like a cheap knock-off.

To be fair, we don't know what kind of environment the pipes are in. Nor do we know what type of pipe (e.g. plastic or metal) or whether the OP wants to measure from the inside or outside. Nor do we know whether this is an industrial question or a consumer one.

All of these things would potentially make a difference to the answer. :grinning_face_with_smiling_eyes:

For example, if I were measuring the temperature of the contents of a pipe from the outside, I would insulate the outside of the sensor anyway and in doing so, would likely use insulation that would seal the device if that were needed.

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To offer a different view on the ds waterproof. I've had three in a very hostile environment for over three years and mine are working great. Maybe mine are the exception. And here we go again on the dht sensors. With all respect to differing opinions, I like them and the several dozen or so I've used over the years have lasted well.

I am just doing some work on a remote Temperature/Humidiy device (SHT30)and using the deep sleep mode on the Wemos then wake up and send a reading over MQTT the current draw in deep sleep mode is only 3mA so it should be fine using a battery pack.

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Some random hopefully useful pages

A doc someone put together with a load of ESP32 (big brother of ESP8266) boards on - useful thing being some have battery charging circuits built in. ESP32 Boards Comparison - Google Sheets

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OK, well that's fine if you find them useful. :grinning_face_with_smiling_eyes:

It is just better to steer others towards better and more reliable sensors. I still have a bunch of the DHT sensors and they were all well over 10% off for temperature and 20+% off for humidity even when new. They are known to drift over time as well. In addition, they don't handle >90% humidity well (common in bathrooms for example). I'm currently using a mix of BMP/E and Si7021 sensors. Last time I looked, the DHT sensors from AliExpress were actually coming out more expensive as well.

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48d with an 18650 isn't so good if you end up with a hundred of them scattered through a factory or even 1 that is the other end of the country :slight_smile:

Yes, of course it is perfectly possible to configure for low-power, I'm just saying that there are potentially better options if you really need to optimise them. Again, we don't know from the question just how far the OP needs to go.

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The BME/P-280 is one of my favourites especially if you want to measure humidity and pressure as well as temperature.

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Apart from the terribly confusing naming that Bosch insist on - I have to look it up every single time! Which has pressure and which has humidity? :rofl:

The Si7021's are just as good as far as I can tell. All about the same price last time I looked.