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 scheduleo 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-switchingo PC software application

• Parents will have ability to limit video game console use

• Automation and security are possible target markets

Technical Constraints   

• Real Time Clocko Must operate at all times, under all power

conditions • Timing Schedule Accuracy 

o Must include Years, Months, Days, Hours, Minutes, Seconds

• User Interfaceo PC is required to operate

• Internal Power Supplyo 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 safetyo UL 758 standard for appliance wiring materialo 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 $50o Retail at ~$100o Comparable products retail from $40 to $90o 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

Approach Pros Cons

Computer Based Programming Software

Cheap Easy to navigate Upgradeable

Requires programming cable

Onboard LCD and Keypad

Independent Limited resolution Requires additional power Expensive

Battery BackupApproach Pros ConsLTC690 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

DS1307 - Real Time Clock Calendar IC

Built in low power draw

battery backup dock Only powers RTCC IC

Redundant design

Microprocessor

Approach Pros ConsPIC24FJ64GA002 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

Approach Pros ConsBTA140-600 TRIAC Solid State

Inexpensive Small footprint

Requires a heatsink Requires optoisolator

T90N5D12 Relay Simple installation Expensive Noisy Large

Power Supply

Approach Pros ConsTransformer + Diode Bridge combination

Proven design Multiple parts Weight Expensive

BP5063-5 AC/DC Converter

Compact package Inexpensive

ScheduleDate Deliverables Project

9/8 Problem Statement - Final Order Parts - PIC(s), USB-to-RS232, TRIAC

9/15 Design Constraint - DraftParts Arrive - Start Breadboarding. Design test program to cycle hardware.

9/22 Design Constraint - FinalExtended Breadboarding/Prototyping. Begin Schematic design

9/29 Midterm Presentations Continue working on hardware prototype

10/6 Midterm Presentations Continue working on hardware prototype

10/13 TBA Finalize Hardware

10/20 TBADevelop software breakdown and begin coding PC software interface

10/28Progress Review / Approach Draft Continue software development

11/3 Approach - Final Finish software

11/10Executive Summary Overview - Draft Debugging

11/17 Evaluation - Draft Debugging

11/24 TBA Debugging

12/1 TBA Final Project due

References

    [1] Powercords Online, "IDC Plugs - Standards," [Online]. Availible http://www.powercords.co.uk/standard.htm    [2] "Appliance Wiring Material, UL 758." Underwriters Laboratories. http://ulstandardsinfonet.ul.com/scopes/0758.html. Accessed September 16, 2008.    [3] “Isolé® IDP-3050 Plug Load Control.” WattStopper.  http://www.wattstopper.com/products/details.html?id=74&category=122&type=Commercial. Accessed August 27, 2008.    [4] “Bits Energy Saving Smart Strips.” Bits Limited. http://catalog.bitsltd.us/power_strips/. Accessed August 27, 2008.

Questions ?