UMass’s Open Source Data Logger: The Minuteman
To further the state-of-the-art in wind resource assessment the Wind Energy Center at the University of Massachusetts has embarked on the development of a modern data logger. All of the features and conveniences expected in current computer networked and remote managed data systems are included in this data logger.
Unit will be enclosed in a water resistant NEMA enclosure. Fiber is preferred over painted steel which corrodes in salt environments.
Source of power TBD. Possibilities include line — 120vac, photovoltaic, wind turbine Two weeks operation from one 20 A-H gell cell is the target. Implication: 30 mA average consumption. If the target is met, a 5 watt PV panel should be sufficient in most instances.
A local display will as a minimum indicate the status of the logger i.e., logging, standby, power good. Primary interface is to be via PC. Web interface desirable. Wireless 802.11 desirable. (no cables, no proprietary software) Password protected.
Plug removable screw terminals such as by Phoenix Contact. Enables fixed field wiring and logger replacement with simple plug disconnection/connection.
- Provision for standard met measurements will be accommodated.
- Barometric pressure, temperature (two channels), dew point or relative humidity, and insolation.
- Six pulse counting inputs suitable for RM Young, Maximum, or other anemometer sensors.
- Three analog inputs for potentiometer based wind direction sensors.
- Two serial ports (RS-232) for serial input data.
- Self-measurement of internal temperature and system power supply voltages.
- Inputs wired to external sensors will be provisioned with static and lightning protection.
- Optional GPS
- LCD or optional VFD(Noritake) display.
- RS-232 Serial port
- Ethernet RJ45 (Lantronix, typical)
- 802.11 WiFi (Lantronix, typical)
- Precision switched 2.5 VDC excitation for sensors
- USB host: logged data archived to dos files (fat16) on USB flash drive
All manner of serial communication will be accommodated. Satellite, Cellular, POTS, direct wire. Communications with the logger enables configuring of the logger and delivery of the data. 802.11x aka WiFi, will be the preferred communication when the user is at the logger.
Daily data files will be e-mailed to the user. The data files will be zip files, so that they may immediately be opened upon retrieval by the operating system software. Zip files are universally recognized by the major operating systems: Windows, OSX, and Linux. Once opened, the files are non-proprietary CSV files, which can immediately be opened with Excel and most other analysis software. A backup of the data will also be stored on a USB flash drive, in dos format.
All sensors sampled a 1 Hz rate
Averaging interval can be set from 1 minute to 1 hour.
Max, min, mean and standard deviation logged for the chosen interval.
All data saved as dos text files, CSV format suitable for opening with excel or other spreadsheet programs (i.e. Open office, open source)
On power-up the system will operate with a default configuration setting. The default will be all channels logged at a one second interval and averaged to 10-minute data. Modifying the logger settings and operation will be performed via a browser interface. Data can be downloaded either by removal of the USB flash memory or via any of the available connections i.e., wireless 802.11, wired Ethernet, phone/modem, or wired serial.
Development Status of The Minuteman
A prototype has been built. The prototype logger is contained on a single circuit board measuring approximately 7” x 11”. It can be seen in Figure 1 below. The prototype hardware contains all the features outlined in the draft features and specifications. The real-time operation and configuration firmware (as well as hardware modifications) are a work in progress. Currently, the logger’s core functions of measuring pulse events from anemometer sensors has been implemented. Local LCD display drives are coded. The system real-time clock has been implemented. Data averaging code has been done. A minimal user interface via a serial connection is complete. Much is yet to be finished.
Of key significance is that the design of the logger is “Open Source.” Briefly, open source means that the entire design of the logger is freely available to any who will abide by the terms of open source. The physical design, the electrical design including schematics, the firmware including source code, and the HTML code will all be freely available. This is contrary to proprietary systems where all the details of the design are withheld from the user. Our hope is that a community of users, engineers, programmers, hobbyists — anyone with something to contribute — will coalesce around this design to criticize, refine, enhance, and improve this initial offering. The implications are that anyone or any organization that so chooses can license, at no fee, this design for manufacture, for private use or for sale. The only conditions of the license are that the same open source nature of the project is continued in all revisions going forward. A very concise summary of the terms of the license along with all the details of the license can be found at the GNU GPL web site.