Back up power generating door
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Back-up Power Generating Door. Group 21 Kyle Rasmussen Michael Gan Allen Huang. Introduction.

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Back up power generating door l.jpg

Back-up Power Generating Door

Group 21

Kyle Rasmussen

Michael Gan

Allen Huang

Introduction l.jpg

  • This project converts mechanical energy from opening a door into electrical energy for a backup power supply. This green energy solution makes use of an everyday occurrence to protect against intermittent power loss.

Features l.jpg

  • Provides 120Vrms / 60Hz during intermittent power loss

  • Easily deployable on any door fixture

  • Senses power loss and automatically switches to backup power

Block diagram overview of device l.jpg
Block Diagram Overview of Device







dc to ac





Overview l.jpg

  • Mechanical: Transfers wide arc of door swing into spin on a mechanical shaft

  • Generator: Transforms rotation of shaft into electrical energy

  • Charge/storage: Stores energy created from the generator by charging it in a battery

  • Converter: Converts the DC power from the battery into AC power

  • Transfer Switch: Taps into the power from the battery to provide electrical control signals needed for the project to operate as well as controlling to flow of energy between each module

  • Detection: Detects power loss in the main power line and sends the appropriate signal to the transfer switch

Mechanical to electrical introduction l.jpg
Mechanical to Electrical: Introduction

  • This portion utilizes a series of gears to translate the swing of a door into rotational motion.

  • The rotational motion is fed to a generator to convert mechanical energy into electricity.

  • For our device to provide backup power for 15min., each door use must generate 22.5J from the generator.

Mechanical overview l.jpg
Mechanical Overview

  • Capture motion from an opening and closing door

  • Convert Kinetic Energy into Electrical Energy

  • Provide enough energy to charge battery

Capture design l.jpg
Capture Design

  • Mountable with screws

  • Arms made from metal bars

  • Rotates with door for 1.05 rad/sec

  • Changed significantly from original design

Arm kinematics l.jpg
Arm Kinematics

Denavit-Hartenberg Parameters

Gear train and generator l.jpg
Gear Train and Generator

  • Overall gear ratio of 1:128

  • Hand picked gears from local hobby store

  • Placed on machined platforms

  • Generator acquired from power lab

Construction l.jpg

  • Metal Grinder

    • Fashioned arms

  • Customized gears

Testing generator speed with output l.jpg
Testing Generator Speed with Output

Verified rated speed of generator

Determined speed necessary for 14.88V into Buck Converter

Load testing generator l.jpg
Load Testing Generator

Motor-Generator Configuration

Measuring power output in response to different loads

Voltage regulator l.jpg
Voltage Regulator

  • Protects battery from surging generator

  • Must handle voltage swings of +/- 2.5V

  • Limits charging current ripple to +/- 2%

  • Maintains charging voltage at 12V +/- 1%

Voltage regulator16 l.jpg
Voltage Regulator

  • Buck Converter:

    Steps down voltage from generator

  • Hysteresis Controller:

    Feedback control of Buck Converter

  • MOSFET Driver:

    Steps up switching signal from Hysteresis Controller

Voltage regulator buck converter l.jpg
Voltage RegulatorBuck Converter

  • Input voltage ranges from 13.63V to 16.13V.

  • Per specification of the battery, the maximum allowable output current was chosen to be 3.33A.

  • Assuming fswitch = 100kHz, solving for VL = L di/dt and Ic = Cdv/dt yields

    • L = 229uH

    • C = 122.1uF

Voltage regulator hysteresis controller l.jpg
Voltage RegulatorHysteresis Controller

  • Compares Buck Converter output (V-) to Vth

  • Voltage comparator outputs high if V- < Vth

  • Outputs low if V- > Vth

Voltage regulator high side driver l.jpg
Voltage RegulatorHigh-Side Driver

  • Converts output of Hysteresis controller to 18.5V

  • Establishes Vgs > Vth for Buck Converter MOSFET.

Voltage regulator testing buck converter l.jpg

Vin sweep from 12.4V to 17.38V

Voltage RegulatorTesting Buck Converter

Voltage regulator testing buck converter21 l.jpg
Voltage RegulatorTesting Buck Converter

Snapshot of output during testing

  • Conclusions:

    • At the upper level of this sweep, the Buck Converter was still able to keep the output voltage within 1% of the nominal.

    • It is clear that the regulator could handle the 2.5V swing expected from the generator.

    • While the ripple voltage was higher than expected, this is mostly due to the switching frequency it was tested at.

Voltage regulator22 l.jpg
Voltage Regulator

  • What went wrong?

    • An unsuccessful transfer of the regulator to the PCB board

    • On proto-board, Hysteresis not outputting

    • This can be fixed with simple debugging

Driver signals l.jpg
Driver Signals

  • 12V provided by main lead acid battery

  • 15V provided by boost converter

  • 6V and 18V provided by external small batteries


12 V

15 V

18 V

Boost converter l.jpg
Boost Converter

Materials Used

  • Power Inductor – Self wound

  • Schottky diode - MBR360

  • Power MOSFET – IRF540

  • PWM Chip - UC2843, High performance PWM controller

  • Capacitors –frequency adjustment and charging output

  • Resistors – voltage divider for feedback

Boosting operation l.jpg
Boosting Operation

On State

  • Switch 1 is On, Switch 2 is Off

  • Inductor charges / current increases

  • Capacitor discharged across load

  • Output voltage decreases

    Off State

  • Switch 1 is Off, Switch 2 is On

  • Inductor discharges / current decreases

  • Capacitor gets charged

  • Output voltage increases





Component selection calculations l.jpg
Component Selection Calculations

  • Selection of R and C connected to the pins. Aiming for Freq = 100K. Looking at the graph for Timing Resistance vs. Frequency, R = 10K and C= 2nF.

  • Need to select voltage divider to bring to the feedback pin. Output is selected at 15V and internal comparator voltage is 2.5V. This means a voltage division of 1/6 is needed. 120K and 20K resistor is chosen

Boost converter output l.jpg
Boost Converter Output

  • Average output voltage is 14.7V. Ripple occurs when MOSFET switches to discharge capacitor in order to lower output voltage.

Testing the boost converter l.jpg
Testing the boost converter

Line Regulation

  • Varied input voltage and fixed load

  • Measure of how well the boost converter handles various input voltages

    Load Regulation

  • Fixed input voltage and varied load

  • Measure of how well the boost converter maintains 15V

Line regulation tables l.jpg
Line Regulation Tables





Load regulation vs load l.jpg
Load Regulation vs. Load

  • Load Regulation is better for higher loads

  • Ideally you want 0% load regulation

  • Why almost 24% load regulation at 3Ω?

Analysis of load line regulation l.jpg
Analysis of Load / Line Regulation



Increase duty cycle of the switch that drives the MOSFET

Gives inductor more time to charge and less time to discharge

  • Line Regulation in 30%s, Load Regulation in the 10%s to 20%s

  • Discontinuous mode operation - current in inductor to drop to 0A between switching cycles

  • Inductor discharges into capacitor prematurely

Dc ac converter objectives l.jpg
DC/AC ConverterObjectives


  • Transform 12Vdc from a battery into 12Vac

  • Voltage waveform at 60Hz

  • Smooth signal and eliminate harmonics with a filter

Dc ac converter general overview l.jpg
DC/AC ConverterGeneralOverview

  • Voltage Sourced Inverter (VSI)

  • Full Bridge Orientation

  • Switches are Power MOSFETs with reverse-parallel diodes

Dc ac converter switching overview l.jpg
DC/AC ConverterSwitching: Overview

Opposite switching signals to each leg

  • Switching signals generated by astable multivibrator

  • Voltages stepped up through MOSFET drivers

Dc ac converter switching generation l.jpg
DC/AC ConverterSwitching: Generation

Astable Multivibrator

  • Incorporates LM555 timer

  • Thresholds established through voltage division

  • Capacitor voltage triggers state changes

  • Conceptual circuit

  • Provide calculations in appendix to refer to

  • Conceptual waveforms

  • Or real if they are available

Dc ac converter switching generation41 l.jpg
DC/AC ConverterSwitching: Generation

  • To realize a 60Hz square wave with 50% duty

    • C = 11.32 μF

    • RA = 120Ω

    • RB = 1KΩ

Dc ac converter switching drivers l.jpg
DC/AC ConverterSwitching: Drivers

  • 4V to 15V conversion

  • Establish VGS ≥ VTH

  • Two High-side:

    • LMD18400N (inv. & non)

  • Two Low-side:

    • MIC4427 (non)

    • MIC4426 (inv.)

Dc ac converter switches drivers l.jpg
DC/AC ConverterSwitches: Drivers

Signal to Switch 1,1

Signal to Switch 1,2

Signal to Switch 2,2

Signal to Switch 2,1

Dc ac converter inverter output l.jpg
DC/AC ConverterInverter Output

  • Leg one

  • Leg two

  • Signal across load

Signal 1: Inverter output voltage

Signal 2: 555 output voltage

Dc ac converter inverter output45 l.jpg
DC/AC ConverterInverter Output

Measured over 3Ω load

  • Signal 1: Voltage out of Inverter

  • Signal 2: Current out of Inverter

Dc ac converter inverter output46 l.jpg
DC/AC ConverterInverter Output

As the power drawn from the battery

increases, so does the power loss

over the inverter.

However, for the range of loads tested,

the losses turn out to be relatively

proportional, and the overall efficiency

of the inverter remains around 2/3.

Dc ac converter inverter output47 l.jpg
DC/AC ConverterInverter Output

Factors in Power Loss

Pg 473 of Krein

Need datasheet of MOS

Dc ac converter output filtering l.jpg
DC/AC ConverterOutput Filtering

  • Originally attempted to use LCR series resonant filter

  • Balanced Q with L

  • Given Q = 3.4

    • L = 7.633mH

    • C = 921.8 μF

Dc ac converter output filtration l.jpg
DC/AC ConverterOutput Filtration




  • 7.1ohm load (Vrms = 7.87)

  • 3.55 ohm load (Vrms = 4.96)

  • 1.1 ohm load (Vrms = 2.56)

Dc ac converter output filtration50 l.jpg
DC/AC ConverterOutput Filtration

What went wrong?

  • Not Core Saturation:

    • Inductors within volt-sec and amp-turn limits

  • ESR:

    • Inductor had an ESR of 0.69Ω

    • Increased power output meant greater voltage drop

  • Additional Inductance

    • Transformer introduced unaccounted for inductance

    • Filter ceases to be resonant (XL> XC)

Transformer overview l.jpg

  • Step up voltage from inverter to 120Vrms

  • From testing we know

    VPrimary = 8.8Vrms

  • Turns ratio is 8.8:120

Transformer output l.jpg



For 1050 ohm load

  • 1 Inverter output (Vrms = 9.9, Arms = 3.35)

  • 2 Transformer output (Vrms = 130, Arms = 122mA)

Transformer output53 l.jpg

High transformer efficiency implies:

Minimization of Eddy current losses

Minimization of Hysteresis losses (i.e. small Hysteresis loop)

This makes sense, since we are operating at only 60Hz

Transfer switch l.jpg
Transfer Switch

Signal from Inverter (+)(-)

Output (+)(-)

Battery (+)

Battery (+)(-)

Inverter (+)

Battery (+)

Batter Charger (+)

Switch positions no power loss l.jpg
Switch Positions – No Power Loss

  • Main line power is fed through to output

  • Inverter is disconnected from battery so it does not discharge it when it is not needed

  • Battery charger linked to battery to charge it

Switch positions power loss l.jpg
Switch Positions – Power Loss

  • Main line power is disconnected from the output

  • Inverter is allowed to draw power from the battery and feed it across the output

  • Battery charger is disconnected from battery

Relay switching scheme l.jpg
Relay Switching Scheme

Power Loss Detection Relay

Main Line

Main Line


From Charger (+)

12V control Signal

From Battery (+)

High Power Switching Relay

High Power Switching Relay


To Inverter (+)

To Battery (+)

Transfer switch relaying test l.jpg
Transfer Switch Relaying Test

Switch 3

Switch 2

Switch 1

Conclusion l.jpg

  • Project derailed by unforeseen complications in both design and manufacturing

  • End result was a backup power supply