Wireless Home Automation


5 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

56 εμφανίσεις

Wireless Home

Douglas Brown

Eric Livergood

Chris Lotysz


The short term goal of this project was to use a
computer to turn on and off a light, as well as
monitor a door, via wireless communication

The real objective was to create a basic
framework for a home monitoring system. New
devices can easily be added to the system. Only
new hardware for different sensors/controllers
would need to be designed.

Original Design

Base module that communicates to the
computer via serial connection, as well as with
all the external devices

Light control device that reports light status, can
turn a 120 VAC light on and off, as well as to a
dim setting

Door monitor reports open/closed status of the

User interface controls the system and gives the
commands/requests to the rest of the system

Original Design


2.4 GHz Wireless Transceivers (Nordic 24E1)

Basic ACK/NACK Protocol

Frequency Hopping

Original Design

Base and Device General Layout

User Interface

Multithreaded Java Swing GUI


changes can be made with
a single click

Real time updates of wireless devices
statuses as they are collected

Easily expandable code to include future
devices and controls

Control Loop

Device Communication Thread

Check Event Queue for new actions to

Perform actions, as needed

Gather all Light Statuses

Gather all Door Statuses

Serial Communication

To perform any action or request, the
program sends 2 bytes

Byte 1: Address of device

Byte 2: Command/Request

Wait for confirmation from base station

Response will always be 1 byte containing the
status of the device request/command was
made to


Serial Port Interrupt:

When data is sent, a flag is set to true to tell
control loop to begin waiting for response

When data is available on the serial port, a
flag is set to tell control loop to read response

Event Interrupt:

When the user clicks an action, an interrupt
occurs and the user’s action is added to the
event queue


Timeouts are coded into two places in the

The base station reports a timeout back to the
computer if it does not hear back within 200 ms from
the device it is communicating with

The control loop will report a timeout if it does not
hear from the base station within 1500 ms

Prevents timeouts from creating major delays in the
system response

Wireless Communication

Base serves as a dummy module to PC

Underlying communication protocol
transparent to PC

Device modules transmit only when
directed to

Wireless Communication

PC to Device


Success+Status OR Fail

Wireless Communication

Device to Device: Instruction

Wireless Communication

Device to Device: Request For Data

Wireless Communication


Light ON: 0x00

Light OFF: 0x01

Get Light Status: 0x02

Get Door Status: 0x10

Dim Light: 0x4X (X indicates the level of dim)

Wireless Communication

packet.address = GetChar();

packet.operation = GetChar();




//Any calculations or base operations



//Any calculations or base operations

status = SendRequestForData(packet);



System Response

Steps taken to decrease response time:

Increased resolution of checking for data

Decreased the number of bytes sent between
the devices

Only refreshed user interface screen when
changes have been made

Created separate thread to handle serial


Objectives: Wireless communication,
microcontroller, reliable power supply,
interrupter sensor, digital switch control of

nRF24E1 programmer board was chosen
to simplify the blending of wireless
communication with microcontrol

Hardware Con’t

Battery power supply and wall delivered
power supply both necessary.

Battery power for remote, sensor based
modules (door)

Wall power for base station and for
modules with available wall power (light)

Base Station

Power Supply and Transceiver

Wall delivered power instead of 9v

Serial communication from transceiver
board to PC

Light Module

Digital Control of Light with multiple dimming

Light Module Con’t

The relay chosen determines the resistive
path taken and thus the voltage delivered
to the gate of the Triac.

The Triac turns on allowing current to flow
to the light bulb when the gate voltage is
sufficiently high.

The relays are DC controlled via I/O pins
from the transceiver board.

Door Sensor Module

Uses a photo interrupter to determine the door’s
status then transmits its status via the
transceiver board

Door Module Con’t

9V battery supplied power.

Sensor used the 3V regulated power and
the straight 9V battery power.

When door is closed power consumption
is minimal, however when the door is open
the sensor dissipates much more power

Power Analysis


Transceiver sinks 18mA at 3V or 54mW

Always putting out 24Vs on the relays(or120V)

Off(24VAC On(120VAC)

Relay1: 13.4K


42.3 mW

1.0746 W

Relay2: 13K


44.3 mW

1.1077 W

Relay 3: 12.4K


46.4 mW

1.1613 W

Only one relay on at a time

Additional power loss in the triac itself. Heat created and leaked
through a heat sink


Transceiver only ~ 54mW wall delivered

Power Analysis Con’t


9v Alkaline Battery supplied power

600 mAh per 9v ~ 5400mWh

3v regulated and 9v unregulated (Vcc)

Transciever ~54mW


Diode ~40.5mW Open ~ +40.5mW

Life when door is open: 40hrs

Hardware Testing

The dimming resistances were
determined experimentally by controlling a
triac with a potentiometer

Power circuits were constructed and
tested with a voltage meter. No testing for
consistency was conducted, but repeated
checking of voltage showed the voltage
regulator to be reliable

Testing & Development for PIC

7 Phases

Serial Communication

Timer Setup

Simple Wireless Communication

Complex Wireless Communication

Integration of Serial + Wireless

Protocol Implementation

Testing with PC

Software Testing

Created a PIC Simulation

Two computers, one with user interface, the
other with PIC Simulation

Output to console each step

Output the data being sent, the data received,
how the data was interpreted

Ran program with one or all devices off to
ensure timeouts would be handled


Communication interference less than
expected, frequency hopping unnecessary

A very open
ended, easy to use
framework developed for expansion of




Power consumption


Ethical Considerations

Introduction of another potential
surveillance system

Potential for unwanted outsider control

Creating a safe system


Nordic Semiconductor


Professor Scott Carney

Ishaan Gupta

Tim O’Connell