Background

The WebTransmitter has been developed to copy data from the WEB seamlessly into a control system as a 4-20mA signal. Once in the control system, the data can be either merely displayed on the Human Machine Interface (HMI) or used in logic as a Process Variable (PV).

Originally, this system was developed to provide the Alberta Electric System Operator (AESO) System Marginal Price (SMP) to facility operators due to the high volatility of the electricity price. Additionally, the Natural Gas Exchange (NGX) AECO price was also provided so that the operator would be able to compare the operating costs of the two common energy sources, electricity and gas. Note that the end user has to have an account with NGX in order to obtain the gas price.

The original systems included a pc computer with custom software and an ethernet enabled logic solver. With advancements in ethernet enabled Single Board Computers (SBCs), a simple but powerful system has been developed to do this with a single device - the WebTransmitter!

Features

The WebTransmitter has the following features:

  • Input power can vary from 15Vdc to 30Vdc
  • Two (2) isolated 4-20mA loops
  • One set of 5A 30V dry contacts that, by default, close each time the Internet is queried to monitor the health of the system
  • Remote reset capablity
  • External LCD display to provide status information
  • WEB configurabile settings
These features make the WebTransmitter a powerful tool to monitor energy prices and provide information so that one can optimize the facility for cost effective operations.

Links

Included is a short list of related sites that relate to the WebTransmitter:

 

Version History

Version 0.1.S - In Progress
  • Serial output for diagnostics via DB9 connection.
Version 0.1.R - February 18, 2010
  • Corrected minor bug where WebTransmitter required initial reset after total loss of power (including battery).
Version 0.1.Q - December 16, 2009
  • Update default network configuration settings.
  • Change default settings for port B to be E+3 and 20mA=$1000.
Version 0.1.P - May 21, 2009
  • Add capability to read the three hour forecast price for the AESO electricity price.
Version 0.1.O - May 5, 2009
  • Update internal WEB server and firmware to provide mechanism to calibrate each of the two 12 bit DACs.
Version 0.1.N - April 27, 2009
  • Ensure device only polls internet once when both the outputs are selected to the same source.
Version 0.1.M - April 25, 2009
  • In config mode, the IP address can now be displayed via the 4-20mA outputs.
Version 0.1.L - April 25, 2009
  • Update internal WEB page.
  • Allow functionality to choose output type for each of loop A and B (SMP and/or NGX).
  • Add ability in config mode to drive 4-20mA outputs to 0%, 50%, and 100%.
Version 0.1.K - April 3, 2009
  • Detection of 4-20mA power blocks DAC output; correct so that DAC signal is blocked for correct port.
  • Correct so that SW5 properly puts board into config mode.
Version 0.1.J - March 16, 2009
  • Utilize close connection in HTTP GET to improve speeds.
  • Compile with DC10.50.
Version 0.1.I - March 14, 2009
  • Updated for version 1.1.x of the motherboard.
  • Minor bug fixes.
Version 0.1.H - January 14, 2009
  • Updated for version 1.0.x of the motherboard.
  • Minor bug fixes.
Version 0.1.G - October 6, 2008
  • Re-direct "exit" on WEB config to WebTransmitter.com site.
  • Minor bug fixes.
Version 0.1.F - October 4, 2008
  • Add exit page to WEB configuration.
Version 0.1.E - October 3, 2008
  • Implement WEB based configuration.
Version 0.1.D - September 24, 2008
  • Alpha release.