Programmable Power Relay Mid-semester presentation

Introduction What’s the PPR supposed to do? Control device power using schedule Prevent schedule tampering Minimize need for user input after schedule is set +

Problem Current power strips have few features o No programmable timing schedule o No interactive user interface Few methods to exercise parental control over electronic devices.

Solution "Smart" power strip with enhanced features o Programmable Timing Schedule for AC-switching o PC software application Parents will have ability to limit video game console use Automation and security are possible target markets

Technical Constraints Real Time Clock o Must operate at all times, under all power conditions Timing Schedule Accuracy o Must include Years, Months, Days, Hours, Minutes, Seconds User Interface o PC is required to operate Internal Power Supply o Must supply power to internals from 120VAC Switching Power Rating o Must operate up to 120VAC at 15A (NEMA 5-15 Standard) [1]

Practical Constraints

Health and Safety Must conform to Underwriters Laboratories (UL) standards for safety o UL 758 standard for appliance wiring material o Within the UL 758  Construction  Performance  Thermal and Chemical property tests  Electrical and Flame properties  Manufacturing  Labeling  Production [2]

Economic Must be manufactured for less than $50 o Retail at ~$100 o Comparable products retail from $40 to $90 o Must be able to compete at a reasonable price [3], [4] Isolé® IDP-3050 Plug Load Control Smart Strip Power Strip

Technical Approach

User Interface ApproachProsCons Computer Based Programming Software  Cheap  Easy to navigate  Upgradeable  Requires programming cable Onboard LCD and Keypad  Independent  Limited resolution  Requires additional power  Expensive

Battery Backup ApproachProsCons LTC690 μProcessor Supervisor IC  Effective battery switchover during loss of primary power.  Low current pass-through rating  Unnecessary features  Powers entire μProcessor on battery backup TPS2111 Power Multiplexer IC  High current pass-through (1A).  Powers entire μProcessor on battery backup  Relies on voltage thresholds when switching between power supplies DS Real Time Clock Calendar IC  Built in low power draw battery backup dock  Only powers RTCC IC  Redundant design

Microprocessor ApproachProsCons PIC24FJ64GA002  Inexpensive  Onboard Real Time Clock and Calendar  Unneeded features  No method for powering just the RTCC off of a battery backup.  Inefficient - 4.1mA at 3.3v running at 4Mhz PIC18F2420  Streamline features  Small device footprint  Efficient - 1.3mA at 3.3v running at 4MhZ  Expensive

Power Switching ApproachProsCons BTA TRIAC  Solid State  Inexpensive  Small footprint  Requires a heatsink  Requires optoisolator T90N5D12 Relay  Simple installation  Expensive  Noisy  Large

Power Supply ApproachProsCons Transformer + Diode Bridge combination  Proven design  Multiple parts  Weight  Expensive BP AC/DC Converter  Compact package  Inexpensive

Schedule DateDeliverablesProject 9/8Problem Statement - FinalOrder Parts - PIC(s), USB-to-RS232, TRIAC 9/15Design Constraint - Draft Parts Arrive - Start Breadboarding. Design test program to cycle hardware. 9/22Design Constraint - Final Extended Breadboarding/Prototyping. Begin Schematic design 9/29Midterm PresentationsContinue working on hardware prototype 10/6Midterm PresentationsContinue working on hardware prototype 10/13TBAFinalize Hardware 10/20TBA Develop software breakdown and begin coding PC software interface 10/28 Progress Review / Approach DraftContinue software development 11/3Approach - FinalFinish software 11/10 Executive Summary Overview - DraftDebugging 11/17Evaluation - DraftDebugging 11/24TBADebugging 12/1TBAFinal Project due

References [1] Powercords Online, "IDC Plugs - Standards," [Online]. Availible [2] "Appliance Wiring Material, UL 758." Underwriters Laboratories. Accessed September 16, [3] “Isolé® IDP-3050 Plug Load Control.” WattStopper. mmercial. Accessed August 27, mmercial [4] “Bits Energy Saving Smart Strips.” Bits Limited. Accessed August 27,

Questions ?