This is a great way to include the HTU21 temp/humidity sensor in a project. The HTUxx sensors are widely used temp/humidity sensors with lots of information out there on how to use them with various micros. But they come in the difficult-to-deal-with surface-mount package so putting it on a breakout board makes it accessible to us "normal" makers. I like that they set this up for i2c but the one complaint I have is the solder jumper. I understand that including the pull-up is a convenience feature so the designer doesn't need to do it but a lot of boards already have the pull-up on the i2c bus so you have to de-solder the jumper pads on this thing to use it in these cases. And man... does that suck. The pads are so close to each other that you really need to suck all the solder off of them to make sure there isn't still a thread there. Even with a premium desolder wick it was a challenge. It would have been a lot nicer, in my opinion, to leave those pads clean and let me solder them if I needed the pull-up instead of defaulting it to on.

This review is not only about the HTU21D breakout board, but about SparkFun as a whole.

I was starting to learn electronic (thanks to Arduino) when I fell upon SparkFun and it's been my crush for 2015. I like everything of it, from the website, to the quality of the pieces provided, going through the persons that answer emails, the articles, the lessons..

And all of that with a lighthearted, humorous tone, which make learning as fun as easy.

I am the kind of person who ask lots of question and its always been the an excellent costumer service. Now about the HTU21D piece itself, once the header are soldered and the linked to your Arduino, just launch the example and everything is working.

I bought a breadboard with the same chip on it from elsewhere (can't remember from where though) and it's been a real pain to make the library work. The one from SparkFun works on first try.

Thanks again for all the information, great products, great service. To all, have a great day.

I've now used 3 of these for my weatherstation here in Hilo, HI, where it rains more than 100" per year and the humidity usually hits 100% for at least a few hours per day. In all cases, the sensor has worked fine for about 6 months and then experienced a fairly sudden shift where it would saturate at humidity 118% unless the real humidity went down to 60% or so. This includes sensors that were wrapped in teflon tape, at Nathan's suggestion, and even after I desoldered the chip and replaced it with the version that has a built-in waterproof membrane.

The data sheet claims the sensor is ok with 100% condensing conditions, so it's unclear why this is happening. (Although I noted that the SHT15, another humidity sensor, has this in their data sheet: "Long term exposures to conditions outside normal range, especially at humidity >80%RH, may temporarily offset the RH signal..." It appears this one experiences a similar behavior.)

Very easy to interface using the example code and connection circuit. Well labeled board.

Some discrepancy regarding the necessity of resistors in series when using a 5V I2C. The example code on GitHub recommends a 330Ω resistor in series for 5V, the description in the Hook Up Guide states that one doesn’t need to level shift, and the example code link from the Hook Up Guide makes no mention of the resistors. Still, Five Stars to the SparkFun Team for a clearly marked board and well written connection guide. I really had to dig deep into old files before i found the one file that confused me.

Compared with the recently calibrated equipment at the lab. The temperature appeared very accurate (±0.5˚F) at room temperature. The humidity was less accurate (±5 %RH) at 20%RH. For the price, I am happy with this device! Saving the one last star for a device with more accurate humidity. Maybe the SHT15 will do that for me.

Thank you and Happy New Year!

Hardware & software worked as advertised.

Conflicting information on the hook-up guide. Code and bullet points in hook-up guide say need 10k resistors on datalines for 5V circuit, while further down diagram and text says resistors not required. I tried hooking up the circuit with 10k resistors inline initially with no results using the Arduino Uno R1. I removed the resistors and it started working immediately. Once it was working I am getting good and fast response values. I still need to verify if the reading is accurate but it's good enough for my application.

Haven't had any problems with it so far. Easy to use and provides fairly accurate temperature and humidity readings.

Own two, but only one works.

Plugged it in and got good data, THis was nice compared to the TMP36

I added headers, hooked it up, dowloaded the examples and it worked perfectly. I added a Thing and light sensor and am streaming that data to data.sparkfun.com. No problems!