Best temperature sensor for IOT projects in 2020

Thread Starter

zazas321

Joined Nov 29, 2015
668
Hey. I am planning to build a temperature sensor network using esp32 devices. I am wondering what are the best sensors to use (most accurate, fastest response and overall) for the IOT projects.
I have read about BMP180/BMP280
DS18B20
LM35
DHT22

Myself, I have only tried DHT22 sensor but was quite dissapointed with the results. The response time was extremely slow (im not sure whether thats how temperature sensors supposed to work), but when I take this sensor from indoors to outdoors (10 degrees celcius difference) it takes like 5 minutes to reach the outdoors temperature.

I am planning to maybe grab one or two DS18B20 sensors and see how they behave.

From your own experience, what would you use for IOT projects? Do you have your personal favourite when it comes to measuring temperature>?
 

atferrari

Joined Jan 6, 2004
4,090
How fast the sensor detect changes, depends a lot of how you actually apply them to sense the place / piece you are interested on.

I used the LM135 in my very first project many many years ago, making close contact, tightly inserted in a metallic jacket full of termal grease. More than enough.

If willing to write the code you could even use a lot of diodes (1N4148) of the same batch as sensors, once you manage to know the curve of Vf variation against temperature. Did intensive testing of it, more than maybe 25 or 30 years ago. Warning, they are NOT linear and the curve had no good symmetry. Constant current is an important detail.

While writing this, I recalled that still have a small lot of LM135 in metallic packaging. :oops:

The last time I used the same LM135, was as sensor for a small temperature PID control loop; it was tightly attached to the part being warmed up with no noticeable delay. Tight contact was key there. If you read the datasheet, learnt how to correct the readings to get actual temperature values. Correction is simple. Again, use constant current if you aim to some kind of valid measurement.

When writing the code to handle DS18S20s, found them quite responsive. If precise or not, cannot say; verifying that takes a proper comparison that I could not make at the moment. The datasheet is a must read, of course.

I am rather far from any experience on HVAC but to sense temperature in a room, the location of sensors IS relevant. Example: the place where I am right now is always cold even in summer. Today we are having around 24° C outside but the floor and walls inside are incredibly cold. A sensor quite close to any of them would be lying.

Five minutes is rather bad but make sure to not expect a faster response than what you actually need; pretty much like newbies planing to build their 1st power supply from 1 to 50 V able to provide up to 30 A when in practice, later, they won't go any further of few hundreds of mA at 12V in the worst case.

Buena suerte.
 

Irving

Joined Jan 30, 2016
1,006
DS18B20 is my sensor of choice, they are pretty accurate and respond quite quickly, not seconds but certainly not as slow as DHT22, which is fine for something like greenhouse control.

The version I use is housed in a 50mm long metal probe. which makes contact measurement easy. The last project I used them for was to make differential temperature measurements of the feed & return water flow on heating radiators so I could balance the system (Arduino Nano, 2 x DS18B20, OLED display and a 5v USB powerbank).
 

gramps

Joined Dec 8, 2014
83
I have numerous DS18B20 sensors in use. I find them easy to use with an Arduino or ESP8266. They respond quickly enough for my needs. The ones I use to measure temps in my pond respond to changes in just a couple seconds. Those measuring air temps, maybe 15 seconds or so. If you get a few DS18B20's to try, be sure to use a reputable supplier. Mouser, Digikey etc. Ebay and such is flooded with out of spec sensors.
 

Thread Starter

zazas321

Joined Nov 29, 2015
668
Thanks for all the replies!
Lm35 are good for 0.5+/-C accuracy, 10mV per degC ,easy to interface wide ranging voltage supply, .
What about the self heating problem for the LM35? It is very well known for BMP180 and BMP280 sensors. As they heat up, they slowly deviate from the actual temperature by 2-3 degrees C
 

atferrari

Joined Jan 6, 2004
4,090
Thanks for all the replies!

What about the self heating problem for the LM35? It is very well known for BMP180 and BMP280 sensors. As they heat up, they slowly deviate from the actual temperature by 2-3 degrees C
Use low (constant) current. Read the datasheet in full. There are reccomendations there.
 

Reloadron

Joined Jan 15, 2015
5,646
All things considered for just general temperature measurements I like the DS18B20 temperature sensor. I have also used the DHT 22 and DHT 11 sensors. That said when I choose a sensor I choose it based on application so things like range, environment and other factors are all considered. If I am doing a furnace survey I sure would not consider a DS18B20. :) You choose a sensor to meet the application. That's about it. Considering price buy a few and see if you think they are what you want for your projects. They are economical enough.

Ron
 

andrewmm

Joined Feb 25, 2011
572
Can I ask
what temperature range you looking at measuring
liquid / gas / plasma / solid material ?

There are sensors for all environments,
 

Irving

Joined Jan 30, 2016
1,006
All things considered for just general temperature measurements I like the DS18B20 temperature sensor. I have also used the DHT 22 and DHT 11 sensors. That said when I choose a sensor I choose it based on application so things like range, environment and other factors are all considered. If I am doing a furnace survey I sure would not consider a DS18B20. :) You choose a sensor to meet the application. That's about it. Considering price buy a few and see if you think they are what you want for your projects. They are economical enough.

Ron
Agreed. for most 'human' measurements the DS18B20 is the best allrounder IMHO, but below -30C or above +125C the K-type thermocouple probe + MAX31856 breakout board (which works with other types of thermocouples too) is my goto solution, as used in my aluminium casting furnace.
 

Reloadron

Joined Jan 15, 2015
5,646
Just thought about something:

Best temperature sensor for IOT projects in 2020

May want to rethink that for 2021. We seem to be running out of 2020. :)

Ron
 

Janis59

Joined Aug 21, 2017
1,221
I am using NYMO TSYS 01 and 02 - very good except the difficulty to solder with feet up. One droplet of epoxy on the pcb and with 0,06 mm wire solder to pcb tracks. That is more handy than solder with feet down and let the heat flow via the via, long through the pcb thickness. 01 have 24 bit and 02 have 16 bit sensitivity.
 
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