Computing stuff tied to the physical world

New HYT131 sensor

In Hardware, Software on Jun 30, 2012 at 00:01

The SHT11 sensor used on the room board is a bit pricey, and the bulk source I used in the past no longer offers them. The good news is that there’s a HYT131 sensor with the same accuracy and range. And the same pinout:

DSC 3353

This sensor will be included in all Room Board kits from now on.

It requires a different bit of software to read out, but the good news is that this is now standard I2C and that the code no longer needs to do all sorts of floating point calculations. Here’s a test sketch I wrote to access it:

Screen Shot 2012 06 30 at 00 23 28

And here’s some sample output (measurements increase when I touch the sensor):

Screen Shot 2012 06 28 at 15 39 55

As you can see, this reports both temperature and humidity with 0.1 resolution. The output gets converted to a float for display purposes, but apart from that no floating point code is needed to use this sensor. This means that the HYT131 sensor is also much better suited for use with the memory-limited JeeNode Micro.

It’ll take a little extra work to integrate this into the roomNode sketch, but as far as I’m concerned that’ll have to wait until after the summer break. Which – as far as this weblog goes – will start tomorrow.

One more post tomorrow, and then we “Northern Hemispherians” all get to play outside for a change :)

Update – I’ve uploaded the datasheet here.

  1. Nice chip :-)

    Now what is this outside you speak of, and where can we download it?

  2. Neither RS or Farnell know about it – is there a data sheet around?

  3. You should update the shop too! (and maybe even the price if you want to do that)

    • I’ve added a note – more substantial changes planned for later this summer.

  4. Neat device – unfortunately the spec disallows sustained use in the steamy tropics here where the humidity sits often at 85% plus ! The automated weather stations here usually fall back to a modernised version of the wet/dry bulb thermometer method, complete with a requirement to top up with distilled water periodically.

  5. Humm… this board is very handy for a project. Hope it appears soon. I’ve currently done with a my own PCB mixing things,and now i’ve pirs to add to the project. As i can seen this has space for temp sensor/pirs/ldr and humidity on the board.

    Maybe after jcw summer vacations we can have some!!

  6. Is it just as power efficient as the SHT11? I could only find “Low power consumption” in the datasheet?

  7. To avoid any float, I suggest:

    Serial.print(temp/10, DEC); Serial.print(“.”); Serial.print(temp%10, DEC);

    • Yep, good suggestion. In this case, since it was just a demo, I went for the easy way out.

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