Low power precision analog datalogger with optional LoRa radio
What is it?
A low power wireless datalogger with 6 precision 24-bit analog input channels, 8 MB of flash storage, and ~14 μA sleep current.
Why did you make it?
I really wanted a go-to device for rem…
A low power wireless datalogger with 6 precision 24-bit analog input channels, 8 MB of flash storage, and ~14 μA sleep current.
Why did you make it?
I really wanted a go-to device for remotely monitoring a variety of sensors. I often need to monitor and log data from precision analog sensors like strain gauges, load cells, potentiometers, and thermocouples; as well as digital sensors over I2C and serial. I also usually have to do this in some pretty remote places where power may not be available, or is unreliable.
Generally speaking, doing this properly requires some pretty expensive equipment. I personally am a big Campbell Scientific fan, but if you just need to monitor a hand full of sensors in a remote location, you are going to be shelling out at least a few thousand dollars. For smaller projects, that quickly becomes cost-prohibitive. This is why I decided to create something that can do the job for significantly less cost (and with much lower power consumption).
Basic Specifications
6 differential 24-bit analog inputs with programmable gain amplifier (1 to 128)
Sockets for custom input modules on each precision analog input channel
MOSFET controlled 3.3V output to shut down power to external digital sensors
2.5V Excitation voltage can be enabled/disabled in code to save power with analog sensors.
14 μA sleep current.
4 high speed 12-bit analog inputs (3.3V)
1 x 12-bit analog output (3.3V) (shared pin with AIN0)
Expansion headers
Onboard LiPo charger (with trace-jumper to disable charging to allow for non-LiPo batteries)
Note: This is a 3.3V board, inputs are not 5V tolerant!
Additional Information
A link to initial documentation and example code is below. Input modules for 1/4 bridge strain gauges and thermocouples are coming soon, as well as the info to make your own.
The board is powered by a 250mA LDO regulator. The board itself requires around 50mA when awake and communicating. Additionally the terminals for 3.3V, Switched 3.3V, and the 2.5V excitation voltages are all powered from this regulator. Please keep this in mind if powering peripheral devices.
This board can also be used with the RFM69 radios. I still think they are excellent for many applications, but I don't want to have to keep them in stock just yet. If you would like to use an RFM69 you can either order with no radio and add your own, or send me message before you order. If I have some available at the time, I will install it instead of the RFM95. If there is enough interest in the RFM69, I will add it as an option.
The case bottom is designed with space to hold a 1200mAh LiPo (like this: https://www.adafruit.com/product/258). You can scale down the z axis a bit If you don't need the extra battery space, or scale up to fit a thicker battery.
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