Design and concept

Software layers

The whole system consists of 3 essential layers:

• External systems, which handles
  • the data acquisition or
  • the data analysis
• PVLng as core component
• A database for data storage (at the moment only MySQL via PHP mysqli module)

External systems

The most data storage work must be done by external scripts. They obtain the measuring data from e.g. sensors and push them via API into the system.

In these scripts are simple to use functions defined, which pushes the data and handles errors.

Scripts to push your data to other sides are also available, for photovoltaic plants I recommend PV-Log or PVOutput.

Web frontend

The web frontend consists mainly of

• Channel administration
• Organization of channels in the channel hierarchy
• Charts module for simple visualizations.

PVLng

The system is build (bottom-up) by

• Models handles a very special kind of data/sensor
• Channel types implements a set set of predefined sensor types, each based on a model
• Channels represent concrete sensors, each based on a channel type
• Channel groups handles special needs about grouping or calculation/transformation

Database

The database have mainly 3 tables for channel organization, 2 tables for readings and some helper tables and views.

Data flow

The general information and data flow is like this: