Tuesday, March 22, 2011

Andrew Week 8 Progress Report

Over the past two weeks Ashley and I have been working on callibrating the ADE7763 chip's measurement for RMS voltage.  We began by studying the datasheet's steps for callibration.  Initially we had minimal success but after correcting some code we are now obtaining stable consistent voltage measurements.  Ashley and I plan to continue working with the RMS voltage measurements on Thursday.

To help our callibration efforts I built an accurate current source using a 200W lightbulb.  By using an industry built clamp meter I have verified that the source draws 1.79amps.  This source will help us in our callibration efforts of the rms current using the accurate source method described in the ADE7763 datasheet.

Finally I began constructing the ethernet portion of the circuit.  I used the Ethernet Arduino shield which utilizes the W5100 chip.  To provide the required voltages I also had to install a 3.3voltage regulator (MCP1827S-3302E.)  Also in my design I am not using the regular Arduino device so with the help of Prof. Curry I matched schematics of the Arduino Ethernet Shield and regular arduino to determine necessary connections and any compatability issues.  Shown below is a schematic of the circuit as designed thus far.


Currently I am leaving the SPI portion of the ethernet disconnected because connecting it without modifying the micro controller code will cause an error in communication between the ADE7763 and Atmega 328P.  The ethernet can be connected if the chip selects for both the W5100 and the SD Card located on the board are set high.  So far these two pins are designed to be PB1 and PB0.  Shown below is a picture of the circuit as currently constructed.




Before Thursday I plan to use a signal transformer so that we can very the AC voltage to determine how accurate our VRMS measurements are over a wide range of values.  I also plan to begin looking into the power supply design because three seperate sources will be needed.  These sources will mainly supply a voltage of 5V except the ethernet board which requires 3.3V.  The three sources are required because of isolation between the SPI bus and the ADE7763.  There also needs to be seperate analog and digital sources provided to the ADE7763 for higher accuracy and less noise.  The schematic has been updated to reflect these changes.  There are three different ground symbols.  One looks like an upside down T, one is the standard parallel line upside down cone and the third is an upside down arrow.

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