Electric Energy Cost Monitor (For Energy Conscious People)

1
Electric Energy Cost Monitor(For Energy
Conscious People)

• Team
• Patrick Townsend (EE)
• Tim James (EE)
• Clay Thompson (CPE)
• Chris Reeks (EE)
• Nidhi Singh (CPE)

Advisor Dr. Noel Schulz
2
Abstract

• Design a product that allows any residence to
  check status of their energy usage
• Ensure easy installment of EECM without outside
  aid
• Make available a simple alternative to
  understanding future energy bills

3
Design Constraints

• Non-invasively measures current up to 200 Amperes
• Has physical interface for user to input cost per
  kilowatt hour (cost/kWh)
• Accurate within 2 of actual energy consumed over
  a 1 month period

4
Hardware Flow Chart
User Interface
Sensor
Signal Conditioning
Micro- Processor
Display
5
Previous Semesters Obstacles

• Power (heat) dissipation in the conditioning
  circuit
• Voltage drop inherent in rectifier
• PIC communication with display
• No floating point operations in PIC
• PIC communications with conditioning circuit

6
Semesters Improvements

• Redesigned old circuit
• Button functions now work properly
• Performs floating point calculations in PIC
• Upgraded pic for more memory

7
Original Conditioning Circuit
8
New AC Current to DC VoltageConditioning Circuit
9
Advantages of New Circuit

• Eliminates need for large resistors
• - Less power lost
• - Less heat dissipated
• - No voltage lost over rectifier
• Corresponds better with pic processor
• - Sends less distorted signal to pic
• - Use of buffer to ensure safety of pic
• Increased accuracy with separation of circuits
  and calibration

10
Power Dissipation Calculations

• Worse Case (max load)
• I 5A, R .1?
• Power Dissipated VI (.5 V)(5 A) 2.5 W
• Actual Worse Case (80 max load)
• I 4A, R .1 ?
• Power Dissipated VI (.4 V)(4 A) 1.6 W
• Average Case (31 load)
• I 1.55A, R .1 ?
• Power Dissipated VI (.155 V)(1.55 A) .24 W

11
Money Lost to Power Dissipation

• Actual Worse Case (80 max load)
• P .0016 kW
• t 8760 hr/yr
• C 0.0654 cost/kWhr
• (Pt) C cost per year
• 0.91 per year
• Average Case (31 load)
• P .00024 kW
• 0.14 per year

12
De-bounce Circuit for Interrupt
Need T ? .25 ?s Because of 4 kHz clock
speed Obtained T .2 ms
13
Switch Circuit for LED Back-Light
Display
14
Previous EECM Display
Running Cost Running Time
Previous Cost Previous Time
15
Advantages of New Programming

• Displays time reference for both cost totals
• Decreases chance of accidental setting changes
• Allows cost per kWh to change with a tap of the
  button or held down
• Increased accuracy because of floating point
  calculations

16
Business/Economics
17
Leading Competitor

• Energy Monitor Logger (EML) 2000
• 219.00
• It can monitor up to two 120V loads up to 200A.
  It can be programmed with the local utility cost
  per kWh, and will calculate the cost of energy
  used.
• Cost Difference 19.00

18
Work Still to Come

• Long term analysis
• Test with split core CT
• Program display changes
• Test circuit board
• Package product

19
References

• Triger, L., The Universal Electrical Meter,
  IEEE Instrument and Measurement Technical
  Conference, Boulder, USA, Mar., 1986.
• Microprocessors a Programmer View, Robert B. K.
  Dewer Mathew Smosna, McGraw-Hill Publishing
  Company, NY, 1990 
• Computer Organization and Design, John L.
  Hennessey David A. Patterson, Morgan Kaufmann
  Publishers, Inc., 1998
• Matty, T.C. , Advanced Energy Management for Home
  Use. Westinghouse ABB, Pittsburgh, PA, USA,
  Consumer Electronics, IEEE Transactions,
  Rosemont, IL, USA, August 1989, pp. 584 588.
• Design and Implementation of a Microprocessor-Base
  d Intelligent Electronic Meter, Lai, M.F. Wu,
  Y.P. Hsieh, G.C. Lin, J.L., Department of
  Electrical Engineering, National Taiwan
  University, Taipei, Taiwan, Industrial
  Technology, 1994., Proceedings of the IEEE
  International Conference, December 5 9,
  Guangzhou, China, 1994, pp. 268 272.