The Mini Pearl Logger is a powerful and inexpensive device for logging environmental data. It is based on an Arduino Pro Mini in combination with a real time clock and a microSD card reader. Combining these common electronic components allows logging data from multiple sensors for multiple months. Three different kits to build a Mini Pearl Logger are available at the [KAPtery](http://kaptery.com/products/data-and-control). The [Mini Pearl Logger Kit](http://kaptery.com/product/mini-pearl-logger-kit) is a minimal version that requires soldering and runs a sketch that puts the logger to sleep between logging events to conserve battery power. The [Mini Pearl Pro Logger Kit](http://kaptery.com/product/mini-pearl-pro-logger-kit) includes a TPL5110 low power timer which turns the logger off between logging events and maximizes battery life. The [Mini Pearl Snap Logger Kit](http://kaptery.com/product/mini-pearl-snap-logger-kit) includes a TPL5110 timer, a BMP280 sensor, an FTDI converter, and snaps together with no soldering required. [](https://publiclab.org/system/images/photos/000/023/322/original/FeatureTable.PNG) All three kits include a DS3231 real-time clock which has an integrated temperature sensor and timekeeping is automatically corrected for temperature. Data from this sensor can be read and logged. The Mini Pearl Snap Logger Kit includes an additional external sensor for barometric pressure and temperature, and many other sensors (including I²C, 1 Wire, and Grove) can be connected to any Mini Pearl Logger. [](https://publiclab.org/system/images/photos/000/023/319/original/miniGo_20180107-2413.JPG) _Above: The parts included in the Mini Pearl Snap Logger Kit. Everything needed to log temperature and barometric pressure for many months (except three AA batteries) is included. An FTDI converter (red) for connecting the logger to your computer is also included._ This logger is based on Ed Mallon's [Cave Pearl Logger](https://edwardmallon.wordpress.com/2015/10/24/diy-arduino-logger-build-instructions-part-1/) which uses a similar combination of components. Ed has done extensive testing to extend the field longevity to more than a year. [](https://publiclab.org/system/images/photos/000/023/318/original/miniGo_20180107-2448.JPG) _Above: An assembled Mini Pearl Snap Logger. The six components are connected with DuPont wires which slide onto header pins on the PCBs. It takes about 15 minutes to get one finished and logging data._ ###Parts Primary components: - **Arduino Pro Mini**. Pro Minis are available on [eBay from sellers in Asia for under $2.00](https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=Arduino+Pro+Mini&rt=nc&LH_BIN=1). At US retailers prices are between $4.00 and $20.00. Pro Minis come in 3.3v and 5v versions, and the 3.3v version is required. - **Adafruit TPL5110 Low Power Timer**. Available from [Adafruit for $4.95](https://www.adafruit.com/product/3435). - **DS3231 real time clock**. This module is available on [eBay for about $1.20](https://www.ebay.com/itm/Top-1-2PCS-Arduino-DS3231-AT24C32-IIC-Module-Precision-Real-Time-Clock-Memory/182840998778?hash=item2a922c3b7a:m:mkMwmF_bfaCkRIqfFG3yeTw) or from [US retailers for $4.00 to $15.00](https://www.amazon.com/Diymore-DS3231-AT24C32-Precision-Arduino/dp/B01IXXACD0/ref=sr_1_5?s=electronics&ie=UTF8&qid=1513187359&sr=1-5&keywords=ds3231+real+time+clock+module). Some DS3231 chips do not work at temperatures below 0°C, but these are not included in KAPtery kits. - **3.3 volt MicroSD card socket**. These modules are available on [eBay for less than $1.00](https://www.ebay.com/sch/sis.html?_nkw=10pcs+Mini+SD+Card+Module+Memory+Module+Micro+SD+Card+Module+for+Arduino+AVR+ARM&_id=331907413969&&_trksid=p2057872.m2749.l2658). There are many different microSD card modules, and some are better at low sleep current. Also required: - **Battery or battery case** for AA or AAA. The Mini Pearl Logger is a 3.3 volt device. Three alkaline batteries (3 x 1.5v = 4.5v) are adequate or four NiMH (4 x 1.2v = 4.8v). LiPo or LiPoly batteries (3.7v) are also good. - **MicroSD card**. Cards of 1 GB or smaller capacity are best if the logger will be slept (instead of turned off with a timer) because they tend to sleep better and at lower current. - **CR2032 coin cell** battery for real time clock. ###Assembly There are documents with guidance about assembling and getting started with the Mini Pearl Loggers at the [KAPtery Guides page](http://kaptery.com/guides/). ###Software A different Arduino sketch for each version of the Mini Pearl Logger can be downloaded at the [KAPtery Guides page](http://kaptery.com/guides/). Below are some research notes about activities done with Mini Pearl Loggers. Some of these notes include the sketch which was used in the activity described. ## Activities [activities:mini-pearl-logger] ## Questions [questions:mini-pearl-logger] ...
| Author | Comment | Last activity | Moderation | ||
|---|---|---|---|---|---|
| komugi | "Were you ever able to see how the TDS data given by the sensor compared to the actual TDS level of your water? " | Read more » | over 4 years ago | |||
| cfastie | "Low power operation: To run your data logger for a long time on small batteries, you can put the Arduino and other components to sleep between log..." | Read more » | over 5 years ago | |||
| pdhixenbaugh | "@cfastie I have 6 weeks (weekends) to get this set up and running for the lake at my summer camp. I don't have the low power timer, but I am going ..." | Read more » | over 5 years ago | |||
| marsh_jasonh | " Oh, that's awesome - That gives me the info I was looking for, thank you very much, really helpful! " | Read more » | over 5 years ago | |||
| cfastie | "The specs for the TPL-5110 timer IC say it can time intervals up to 7200 seconds (2 hours). It seems unlikely that it could be extended beyond that..." | Read more » | over 5 years ago | |||
| marsh_jasonh | " Obviously kind of an old article, but I am just getting into arduino and electronics in general. My question is I have a similar project to this ..." | Read more » | over 5 years ago | |||
| liz | "This is so useful! Another imaginative concept brought to real world utility by Chris Fastie. If I ever have a well, I will install this to learn a..." | Read more » | about 6 years ago | |||
| warren | "Tremendous! :tada: " | Read more » | over 6 years ago | |||
| MadTinker | "Just a quick update on the status of this project. Willow Creek is going through a couple of serious events. First, the stretch of the stream where..." | Read more » | over 6 years ago | |||
| MadTinker | "@cfastie FWIW I used a Kalman filter algorithm for my TDS analyses with data from a similar setup data logger setup. I believe that my original im..." | Read more » | over 6 years ago | |||
| cfastie | "What do you guys think, is it okay to use the mean instead of the median? @pdhixenbaugh, @MadTinker, @Shanlter, @rockets " | Read more » | over 6 years ago | |||
| hpprinter1995 | "Nice And Informative Website. Please Keep Continue Such Kind Of Effort. Contact Us And Get On-Site HP Printer Support & HP Scanner Support. Our..." | Read more » | over 6 years ago | |||
| pdhixenbaugh | "I'm also looking to measure Conductivity, and I have a Riffle. So you have any advice for what sensor to buy, with the memory constraints and other..." | Read more » | over 6 years ago | |||
| Paquicamus | "I have done many calibrations to correlate Conductivity vs TDS. One thing that I have found out it will only work for one Creek, river or any surfa..." | Read more » | over 6 years ago | |||
| cfastie | "Fig. 6 was created using Fritzing (http://fritzing.org/home/). The annotations and some editing were then done in PhotoShop. " | Read more » | over 6 years ago | |||
| overwriter | "@cfastie Cool project. I'm try to create a diagram similar to Figure 6. How did you go about creating that? " | Read more » | over 6 years ago | |||
| warren | "Oh no! I recycled the sour cream containers. We'll have to go eat some sour cream now. :-) I'm hoping it'll be possible to attach these to a stake..." | Read more » | almost 7 years ago | |||
| xose | "Amazing Christian!!! " | Read more » | almost 7 years ago | |||
| cfastie | "Yes, I agree that this is a different approach to an issue that has had a lot of effort directed at software solutions. This is a purely hardware s..." | Read more » | almost 7 years ago | |||
| warren | "Wow, this is really cool. I'm thinking about how to break out some of this info into a low-power-data-logging section or something. Would it be hel..." | Read more » | almost 7 years ago | |||
| cfastie | "The Mini Pearl Logger in the compost pile stopped logging today when the battery voltage dropped too low. Four AAA eneloops ran the logger for 13.5..." | Read more » | over 7 years ago | |||
| cfastie | "I checked on the Mini Pearl logger in the compost pile today and swapped SD cards. It was still logging after 7.5 days, so that's a new record. I n..." | Read more » | over 7 years ago | |||
| EdMallon | "I found that pulling up the three lines usually helps the cards sleep faster. Unfortunately this is completely controlled by the sd controller circ..." | Read more » | over 7 years ago | |||
| cfastie | "Thanks Ed, I disabled the LEDs and deployed the Mini Pearl Logger in the compost pile again. The batteries lasted 6.5 days instead of 2.3 days. So..." | Read more » | over 7 years ago |