The Bat Call Data Recorder
( Using an Arduino based platform )

My last bat activity logger became obsolete when the commercially available data recorder it used was discontinued ... after only a couple of years in production. Over 50 of those loggers had been built and deployed, and many seemed to feel they were useful devices. A lot of effort went into keeping the cost that logger down, and yet it still cost $300 to produce. So now the challenge was to see what would be the next generation of bat logger to evolve.

Frank and I had been experimenting with the Arduino platform, and it's potential to be used for logging bat call data and bat activity. We developed the ArduBat, which has been in use for over a year now, and have found it quite capable in terms of collecting bat call information. While the ArduBat is excellent for experimenting with the Arduino, we needed to reduce power consumption, and costs, to make a truly viable bat call data logging system for widespread use. And this time, we would design and construct all the components ourselves ... we didn't want another design to go extinct if the market changed a little again.

The resulting Bat Call Data Recorder ( BCDR ) is composed of two specially designed components ... the Data Recorder Platform ( DRP ), and the Bat Call Sensor shield. The modules are somewhat compliant with design of the Arduino UNO, which provides for a rich development environment that really makes the project more readily achieved.

There is an optional enclosure for the BCDR, but it is also available as a bare boards assembly. I have found that many times researchers prefer to package their own equipment according to how they anticipate deploying it. They may want buried boxes, pole mounted NEMA cases, or just plastic boxes. The system is easily mounted to anything with industrial strength velcro ... just as it is shown mounted to a battery at the left.

The best thing about the simple design is that the total cost for the parts is less than $100 !! So the cost of a bat activity logger drops by two-thirds over the last design !!

The data collected by the Bat Call Data Recorder is defined by the software written for the ATMEGA-328 processor on the DRP. The program I am currently using attempts to record every bit of information that can be gleaned from the pulses that the Bat Call Sensor collects.
To the right is a sample datafile printout from my original program.

Each ten minute period has an activity present graph line that indicates if bats were heard in any of the 10 one minute intervals of that ten minute period.

At the end of ten minutes, the activity for that 10 minute interval is given an Activity Index value ( AI ). Then the lowest, average, and maximum bat call frequency ( Frq ) is printed, followed by the lowest, average, and maximum time between calls ( TBC ) for that period.

At the end of an hour, the hourly Activity Index is calculated and printed, along with the current temperature and battery voltage.

Note: The format of this program's output file was last revised in March of 2016. It is no longer my standard program for the BCDR, but is still available as a special request option.

The start and stop times for recording bat call data are defined in a simple text configuration file on the SD card. That file also has a parameter that defines what voltage level the battery can reach before the logging system is totally shut down. This preserves the battery from failure from over discharging.

The time and date for the RTC is also set by creating a special text file on the SD card, and then running the logger.

UPDATE: March, 2016

I have finished a second program that records data in a single line format that can be easily imported into a spreadsheet program ( I use Excel ). This is now my standard program for the BCDR.

A sample of the output is shown to the right.

All of the configurable program settings are displayed in the first lines of data. If start and stop program times are used, a programmable separator line can be inserted to show the break in time.

Data collection intervals of 1, 5, 10, 15, 20, and 30 minutes are supported. The relative sensitivity of the event counter can also be programmed.

UPDATE: April, 2017

An optional enclosure has been identified for situations where more protection for the BCDR circuitry is required. The enclosure is not waterproof, but it is weather ( dust ) resistant, and will provide robust protection of the electronics.

The enclosure accommodates the BCDR boards with enough room to allow accessing the SD card.

The wire battery leads simply pass into the enclosure through two holes in the back panel, and connect to the screw terminal strip.

The RTC battery is inserted or replaced by pulling up gently on the Bat Call Sensor board and separating it from the Data Recorder board. The front panel of the enclosure will come along with the Bat Call Sensor.

The BCDR circuit boards are mounted into the enclosure with Velcro.


At this point, the program has been well tested. The hardware is finalized. An enclosure has been identified. I think the design is complete !

Please feel free to email me if you have any questions or comments regarding the Bat Call Data Recorder.

Tony Messina - Las Vegas, Nevada - email: T-Rex@ix.netcom.com - First published January, 2015