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Power Gnome... never generate kilowatts of power alone.
Fri. May 04, 2007: Final
State University of NY
at Buffalo
EE: 494
Capstone Design
Spinelli, Yore
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Mandate for design
UB Green under Walter Simpson are developing a solar powered exhibition trailer.
Specification: April 30th 2007Construction: Fall 2007
Photovoltaic power production to reach 2.8 kilowatts / hourConsumption will vary
But how do we keep track of it all…..?
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…. The POWER GNOME!
A autonomous datacenter that monitors:
PV array voltage
the main power bus voltage
PV array current output
Charge controller output current
Main power bus output current
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PV Trailer Power Layout
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Characteristics
• Real-time oscillo-graph display
• Automatic time/date stamped logging– Open format/Excel
readable
• Practical Validation of PV power production
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Education
• ‘How Efficient Am I?’ template– Visitor estimation of home power use and potential
savings• PV Sizer
– Allow visitor psudo-design of PV system• PSPICE
– Visitor demo of EE design software
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Entertainment
Spool Multimedia playlist to PV trailer PA system
Queue conservation and environment action
videos
Able to display a 640x480 video and maintain normal
operations
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State of Charge Monitor
• Sample half-rail voltage
– 60% depth of discharge, audible alarm
– 80% depth of discharge, cut off all power
• Obviously, also disables power to the Gnome, but reserve monitor continues to function
Final product has built in Hysteresis (relay pull-in vs. drop-out)
Power returns at 40% depth of discharge
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Bringing the Gnome to Life
• PV environment dictates extreme low power• VIA C3 Eden embedded microprocessor @ 11 watts
– Carbon Neutral item @ Pentium III / Gen 1 P4 performance
• Complete item nominal @ 34 watts
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Design Highlights
Current flow measurements @ the mV level
Utilize operational amplifiers to ramp into a 0 to 5 volt
working range .
Inverting Differential design implemented for PV
panel output current & charge controller output
current.
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Design: Sensory Drivers
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Design: State of Charge Monitor
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Programming Highlights
MS-Dos Batch configuration of bootup, system
maintenance, etc.
Modified initialization files for ‘Tracer DAQ’.
Autolaunch with predefined trace configuration and
logging parameters.
How-To guide for ‘quick-n-easy’ startup.
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Known Issues:
[1] - Tracer DAQ suffers buffer overflow
- Solutions:
a- MCC SDK
b- further analysis of initialization routine to rectify
issue.
** Gnome will be ready for practical use after this is
addressed.
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Demonstration
Startup
Real-time display
Log system
How Efficient am I?
PV Sizer (region 695 = WNY)
State of Charge Monitor