Cave Pearl Data Logger: A Flexible Arduino-Based Logging Platform for Long-Term Monitoring in Harsh Environments
- Built from a small number of low-cost, readily available components
- Supports a wide variety of analog and digital sensors
- Non-proprietary software and file formats
- Removable microSD storage media
- User-adjustable operating parameters, such as sampling interval
- Operating life span > 1 year using alkaline AA batteries transportable on most airlines
- Rugged, chemically resistant environmental housing for submerged or buried deployments
2. Data Logging Platform and Principles of Operation
3. Environmental Housings
4. Sensors, Communication Protocols & Resolution
5. Data Logger Software
6. Power Considerations for Maximum Run-Time
6.1. Optimizing Sleep Current
6.2. Optimizing Run-Time Power
6.3. Comparison of an Event Logger Duty-Cycle, without and with Run-Time Power Optimization
- Sensing an event: triggered when a drip impacts the housing (Figure 9a). An intermediate delay is required for damping of the vibrations before the movement threshold alarm can be re-enabled;
- Time Series event: At the end of each sampling interval the RTC alarm triggers a reading of the ambient temperature and writes that with the time-stamped count data to the EEPROM (Figure 9b);
- Transferring all buffered data from the EEPROM to the SD card, which occurs when the memory chip on the RTC module is full (Figure 9c).
- Delay statements were replaced with brief processor sleeps
- PRR settings disable all internal peripherals except Timer0
- The I2C bus clock was accelerated to ~400 kHz
- SPI transfer speed was doubled when initializing the SDfat.h library.
6.4. Power Considerations: Conclusion
7. Case Study 1—Monitoring Vadose Zone Hydrology Using Drip Counters
7.1. Nature of the Problem
7.2. Drip Counter Construction
7.3. Field Deployment
7.4. Performance and Validation
8. Case Study 2—Tracking Water Flow in a Flooded Cave System
8.1. Nature of the Problem
8.2. Flow Meter Construction
8.3. Field Deployment
8.4. Performance and Validation
Conflicts of Interest
|Data Logging Platform|
|Generic 3.3v 8MHz Pro Mini clone [328P]||eBay||$2.00|
|DS3231 & AT24C32 I2C RTC Module||eBay||$1.25|
|CR2032 RTC battery||eBay||$0.50|
|(2) 12mm M2 nylon standoffs for RTC||various||$0.40|
|microSD card adapter for Raspberry Pi||eBay||$1.00|
|128-256Mb microSD (Nokia, Sandisk) (used)||eBay||$3.00|
|3xAA series, or 3 single AA plastic battery holders||eBay||$1.00|
|Deans T-Style Battery Connector||eBay||$1.00|
|4 inch or 2 inch Oatey Test Cap||Menards [#39103/#6893208]||$0.50|
|(2) WSD1241 Micro 4B Plug||Advantage Hobby||$3.00|
|Misc parts: wire, caps, resistors, LED, etc||various||$1.50|
|Total in US Dollars:||$15.15|
|Drip Sensor Housing (Case study #1)|
|FERNCO QWIK Cap, 4 inch||Menards [#QC-104]||$3.90|
|4 inch PVC Drain Cap||Zoro Tools [#G6182477]||$1.25|
|Charlotte 4-in dia PVC Test Cap||Lowes [#23408]||$2.05|
|ADXL345 accelerometer module (w 3.3v input)||eBay||$2.00|
|Total in US Dollars:||$9.20|
|Flow Sensor Housing (Case Study #2)|
|(2) 2 inch Formufit white table caps||Home depot [#F002ECT-WH-4]||$4.50|
|(1) Formufit End Cap, 2 inch Slip fit||Home depot [#F002EEC-WH-10]||$1.60|
|(6 inches) Formufit 2 inch Sch. 40 PVC pipe||Home depot [#P002FGP-WH-5]||$1.50|
|2 inch Schedule 40 PVC slip fit coupling||Menards [#K00955T]||$0.50|
|(2) 1/2 inch NPT Threaded PVC Plug Sch. 80||Zoro Tools [#G2988937]||$2.80|
|332 O-Ring, EPDM, 3/16 dia.||Zoro Tools [G2506561]||$1.00|
|(3) 3-1/2 inch, 1/4-20, Nylon 6/6 Hex Bolt, Slotted||Amazon||$1.00|
|OR: Threaded Rod 1/4-20 x 4 ft, Nylon||Zoro Tools [#G0540757]|
|(3) Black 6/6 Nylon Hex nut, 1/4-20||Zoro Tools [#G2205567]||$0.25|
|Epoxy, Loctite Hysol 30-CL, 50mL||Zoro Tools [#G2233901]||$1.50|
|GY-511 LSM303DLHC Module||eBay||$3.00|
|Total in US Dollars:||$17.65|
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|Techniques for Optimizing Sleep Current||Approximate Reduction|
|Put the microcontroller into the deepest power down modes between readings||5 mA|
|Disconnect ‘always-on’ indicator LED’s on the Arduino and on sensor boards||~5 mA each|
|Choose 3.3 V sensor IC’s with low-power sleep modes||0.05–0.1 mA each|
|Power the RTC from an Arduino output pin, rather than the 3.3 V rail||0.09 mA|
|Remove power from sensors/devices via a transistor controlled by a digital pin||sensor dependent|
|Test and select SD cards with the low sleep current||0.05–0.1 mA|
|Select an Arduino that uses a more efficient MCP1700 series regulator||20–25% savings|
|When combined, these techniques can reduce a data logger’s sleep current to ~0.1 mA.|
|Techniques for Optimizing Run-Time Current||Approximate Reduction|
|Put the processor to sleep while waiting for sensor readings||5 mA × Δt|
|Use higher bus speeds to accelerate sensor communication||5 mA × Δt|
|Select sensors that use less power while taking a new reading||Up to 5 mA × Δt|
|Use green indicator LEDs with large limit resistors||2 to 5 mA × Δt|
|Disable on-chip peripherals with Power Reduction Register settings||0.01–1.0 mA × Δt|
|When combined, these techniques can reduce average run-time currents by up to 90%|
|Charge required (mAs)||0.2324||0.4056||5.980|
|Charge required (mAs)||0.0050||0.0403||2.496|
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Beddows, P.A.; Mallon, E.K. Cave Pearl Data Logger: A Flexible Arduino-Based Logging Platform for Long-Term Monitoring in Harsh Environments. Sensors 2018, 18, 530. https://doi.org/10.3390/s18020530
Beddows PA, Mallon EK. Cave Pearl Data Logger: A Flexible Arduino-Based Logging Platform for Long-Term Monitoring in Harsh Environments. Sensors. 2018; 18(2):530. https://doi.org/10.3390/s18020530Chicago/Turabian Style
Beddows, Patricia A., and Edward K. Mallon. 2018. "Cave Pearl Data Logger: A Flexible Arduino-Based Logging Platform for Long-Term Monitoring in Harsh Environments" Sensors 18, no. 2: 530. https://doi.org/10.3390/s18020530