Enter the SHT30

tmpFF8AThe SHT30 is a chip able to measure temperature and humidity and it is very tiny. It is available on a “shield” board for as little as £1.76 including shipping – and will work with any system able to handle I2c – such as my own ESP8266 kitchen-sink code.

Now, ask yourself,  why would we want yet another temperature/humidity chip?

Don’t we already have the DHT11 and similar? Read on.

So first things first. For temperature we have the excellent Dallas DS18b20 – a 3-pin device (power, signal, ground) which can even run on parasitic power and hence be classed as a 2-pin device. We have the DHT11 and DHT22 and others, able to measure temperature, humidity and when it comes to the BME chips - even pressure (and incidentally ALL of this are already working on my ESP8266 software.

Well, limiting the conversation to those chips/boards able to handle both temperature and humidity, the DHT11 is rubbish – it’s the blue unit you see on many of these kits featuring a million sensors. It does not last long, is cheap and nasty and not very accurate.  The DHT22 on the other hand, lasts longer and is accurate. It is also nearly (or more than) twice the price of the SHT30.

Claimed accuracy for the SHT30 is +=3%RH and +-0.3C -  hence as I’ve done elsewhere I’ve limited reporting to the nearest integer – something I’ve always found just fine for heating systems and other applications.

Nothing new to learn here if you’re familiar with my code – the new number is 5 – that is {temp_type:5} and you are up and running.

A couple of things to note. This particular board has no regulator and so in my case, not using a WEMOS ESP, I used ground, 3v3 and D1 and D2.  Please note that they seem to have screwed up SCL and SDA – because when using this with the larger WEMOS ESP8266+SSD1306 display board, I had to cross over D1 and D2 to get the board to show up on the system. No matter. I have a command {i2c_scan} for that.

If you are doing your own thing note that this chip is particularly easy to drive, fire two values out to the I2c and read  back 6 values – and you only need 4 of them. There is a 0.5 second delay between starting the chip off and reading values… I get around that delay by only using it the first time I take readings – from there on the LAST thing I do is trigger the sampling – so that it is ready and waiting for the next time around. This also works well for the Dallas chip. See also support for the BMP and BME I2c chips – the latter is lovely – but not cheap.

For more info on the ESP8266 software see the Home Control 2017 blog entry. There is a “library” here for Arduino/ESP8266 people – but really – very simple…

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19 thoughts on “Enter the SHT30

  1. Please note - any question on this chip - you might want to consult our friend Google as I'm travelling for the next few days (but with a pile of interesting post expected late in the week!).

    1. I am at a total loss as to how it is that the Italian site is often cheaper than the main international site - but you are correct. £1.35 including postage to the UK - amazing - and ordered...

    1. Yes, indeed, much smaller... very handy. Cost is always critical though because you're competing with other similarly priced items. At under £1.50 that first one may not be as pretty - but it seems unbeatable.

        1. For clarification:

          BMP280 = pressure (based on altitude) and temperature
          BME280 = temperature, humidity and pressure
          SHT30 - temperature and humidity
          DHT22 - temperature and humidity
          DALLAS - temperature

  2. I had some problems using the WEMOS SHT30 shield with the WEMOS D1 Mini Board under the SHT30: it produced a lot of heat, so the SHT30 measurements where about 2 degrees higher than expected. Sadly the humidity values are influenced by the temperature, so they are also somehow wrong.

    So before using that combination, check the results against another temperature probe nearby and calibrate the SHT30 readings in software. I ignored the possibly wrong humidity values, because I don't know the correct relation between temperature and humidity.

    1. I make good use of the double and triple WeMos base boards so that I can mount the ESP8266 module to one side of any sensor rather than above/below as I too originally had issues with WeMos sensor shields getting warm, especially when mounted in an enclosure.

      Dual Base: -

      https://www.aliexpress.com/item/WEMOS-D1-mini-Dual-Base-Shield-Double-Socket-NodeMCU-ESP8266-Board-for-Arduino-Wholesales-in-Stock/32744703872.html

      I can't find a link to the recently introduced triple base right now (not sure if they are genuine WeMos items either as there are a lot of clone boards and shields out there).

        1. Ahh well spotted. I bought quite a few when I first spotted them for sale and I buy so much stuff from both Banggood and AliExpress and constantly price compare that I forget which stuff I bought from which Chinese site!

          The triple boards are my favourite as it means you can have an ESP, a sensor and a small OLED all side by side in a project.

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