This is a testing site only. See the live Public Lab site here »

Mini Pearl Logger

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]( The [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]( includes a TPL5110 low power timer which turns the logger off between logging events and maximizes battery life. The [Mini Pearl Snap Logger Kit]( includes a TPL5110 timer, a BMP280 sensor, an FTDI converter, and snaps together with no soldering required. [![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. [![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]( which uses a similar combination of components. Ed has done extensive testing to extend the field longevity to more than a year. [![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]( 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]( - **DS3231 real time clock**. This module is available on [eBay for about $1.20]( or from [US retailers for $4.00 to $15.00]( 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]( 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]( ###Software A different Arduino sketch for each version of the Mini Pearl Logger can be downloaded at the [KAPtery Guides page]( 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
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 » almost 5 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 » about 5 years ago
cfastie "Fig. 6 was created using Fritzing ( The annotations and some editing were then done in PhotoShop. " | Read more » about 5 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 » about 5 years ago
cfastie "The first two times I tried the Rev. P wind sensor, I also tried the Rev. C sensor. The Rev. C sensor did not work as well as the Rev. P, so I focu..." | Read more » about 5 years ago
cfastie "It’s fairly straightforward to use the Modern Device Wind Sensors with either a Mini Pearl Logger or a Nano Data Logger. I had great success with t..." | Read more » about 5 years ago
warren "@cfastie, what do you think? The AREN folks are asking us for some that'd be relatively quick to plug in and start logging on a kite, that could be..." | Read more » about 5 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 » about 5 years ago
xose "Master! Unmeasurable amount of work to get this. Thanks a lot @cfastie!! " | Read more » over 5 years ago
xose "@xose awards a barnstar to cfastie for their awesome contribution! " | Read more » over 5 years ago
xose "Amazing Christian!!! " | Read more » over 5 years ago
warren "@warren awards a barnstar to cfastie for their awesome contribution! " | Read more » over 5 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 » over 5 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 » over 5 years ago
donblair "Great question re: whether powering the Feather on the 3V line really does work well ... I don't really know. But: looking at a schematic for one ..." | Read more » over 5 years ago
cfastie "That's a really good point that the En pin on the Feather can disable the regulator and reduce power consumption. We need a table of all the featur..." | Read more » over 5 years ago
donblair "Thanks Chris -- this is incredibly useful. So important for folks to have a sense of the trade-offs and considerations when choosing solutions in ..." | Read more » over 5 years ago
liz "@cfastie here's the link to the known bug currently affecting the display of replications on the original activity:" | Read more » over 5 years ago
zengirl2 "@cfastie thanks for pointing out that I used the new small SD card module. Your comments about energy savings are also very helpful. Fascinating th..." | Read more » over 5 years ago
cfastie "Leslie, it's really good you got this working. Thanks for troubleshooting the RTC library. It looks like the library I have been using is the MrAlv..." | Read more » over 5 years ago
warren "Wow, super!!! " | Read more » almost 6 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 » almost 6 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 » almost 6 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 » almost 6 years ago