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Description: The SparkFun Photon Weather Shield is an easy-to-use add-on board that grants you access to barometric pressure, relative humidity, and temperature. There are also connections on this shield to optional sensors such as wind speed, direction, rain gauge and soil readings!

These Weather Shields utilize the Si7021 temperature/humidity and MPL3115A2 barometric pressure sensors. Each shield comes with two RJ11 connectors (for optional hookup of rain and wind sensors) and a 3-pin soil temperature and moisture hookup. Finally, each Weather Shield can attach effectively and easily to your Photon in no time at all!

The Particle Photon is a tiny WiFi development kit for creating connected projects and products. Sporting a 120MHz ARM Cortex M3 and built-in WiFi, the Photon is not only powerful but easy to use. The small form factor is ideal for IoT projects with cloud connectivity.

Get Started with the Photon Weather Shield Guide


  • Humidity/Temperature Sensor — Si7021
  • Barometric Pressure — MPL3115A2
  • Headers and Connectors Pre-Soldered
  • Compatible with the Photon and the Core


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Customer Comments

  • Worked like a champ for me. Also had the Battery Shield, big-boy LiPo, nice size Solar Panel, and of course the weather gizmos'. The Photon sends the data to the cloud and my local html reads the data and populates some really cool controls and indicators. Extremely fun project. I call it MANFRED for …









  • legoadk / last month * / 1

    Hello SparkFun, I see you switched from the HTU21D (without protective cover) to the Si7021 (with protective cover). I made the same switch on my old-version Photon Weather Shield when the HTU21D died, too. I desoldered the chip and installed a Si7021 w/cover. An excellent choice, and it definitely helps to keep this board running more reliably.

    But I would like to also inform users that both of these chips have a built-in heater that exists solely to prevent excessive condensation on the sensor in extreme humidity conditions. I deduced that what actually killed my HTU21D was a combination of 1) not being shielded/protected by the cover that the Si7021 has and 2) an extended period of fog - which caused sensor readings in excess of 110% humidity for a few days in a row, non-stop. The sensor could not cope with this condition.

    My code, which was—at that time—based off the code provided by SparkFun, also did not make any use of the heater to prevent this sort of damage, although the provided library does have methods to turn it on and off.

    I suggest using the SparkFun library’s heaterOn() when the humidity rises above 100%, and heaterOff() when the humidity comes back down to something reasonable, like 95 or 98%. Also make sure that you turn the heater off in setup(), just to make sure that you put it in a known state when the unit boots up.

    This also means that you will see temperature fluctuations on the Si7021 of up to two degrees Celsius while the heater is on. For that reason, I suggest switching your primary source of temperature data to the barometric pressure sensor’s built-in temperature sensor, as it is unaffected by the heating element (it’s on a separate IC).

    • Oh cool I’m going to try that. My HTU21D failed and unfortunately I just bought a new board last week, wish I knew about the new change. I was going to try putting Teflon tape over the HTU21D, but now I’ll try both. Also I was going to try to replace the bad HTU21D on the old board. It sounds like the Si7021 is footprint compatible and perhaps I can install an Si7021 on my bad board without any other changes?

      • You are correct, the Si7021 is a drop-in replacement for the HTU21D. You should be able to hot-air the HTU off and add the Si7021 no problem.

        • Awesome, I’ve needed a reason to blow the cob webs out of my hot air nozzle :)

          Also, from the new Library code it looks like the only difference is the ID value from the ID register, other than that they work the same, is that correct?

    • Very good advice. Thank you for that information. I will look into adding that functionality into the library example.

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Related Tutorials

Photon Development Guide

August 20, 2015

A guide to the online and offline Particle IDE's to help aid you in your Photon development.

Photon Weather Shield Hookup Guide V11

March 2, 2017

Create Internet-connected weather projects with the SparkFun Weather Shield for the Photon.