Technion – Israel Institute of TechnologyDepartment of Electrical EngineeringHigh Speed Digital Systems Lab

Project performed by: Safi Seid-AhmadEmile Ziedan

Project supervised by: Michael Itzkovitz

Building a prototype of a device that is capable of detecting object colors for the use of blind people. The system informs the user of the color by a voice message.This device should be:

• Simple to use.

• Portable.

• Inexpensive.

There are various representation models for colors.

We are dealing with RGB model.

The idea behind this model is simply that every visible color can be represented as a combination of 3 basic colors: Red, Green and Blue.

For example:Red Green Blue

Orange 255 128 64

Yellow 255 255 0

Light Source

Light Source Driver

Light Analyzer

Driver

Light

Analyzer

RGB Calculation

Red -Freq

Green -Freq

Blue -Freq

ColorDetermination

Red

Green

Blue

VoiceMemory

Speaker Analog signal

Voice Memory

Driver

Object

OrangeSpeaker driver

Microcontroller

When the user presses the operation button, The light source emits light on the object to be reflected towards the light sensor.

The sensor is controlled by the PIC in order to perform 3 measurements; for Red, Green and Blue components of the object color.

How can the PIC detect the color?

The PIC calculate RGB values by comparing the output of the color sensor to min and max frequencies which have been already measured (see Calibration process).

The RGB values are compared to colors inside a look table, according to that the PIC finds the color with the closest RGB values to the calculated RGB of the object.

How would the user be informed?

The user is informed of the color by a voice message. Messages declaring the colors in the table are stored in a voice memory controlled by the PIC microcontroller.

When using the TCS230, it is necessary to do a ‘white calibration’ before taking any readings to counteract any offsets or environmental effects.

For instance, if your light source is white but has a blue component to it, then it will give a higher reading on the blue channel.

This can be calibrated out in the TCS230 by having the sensor stare at a white target and bringing the values of each of the channels to maximum.

One option is the TCS EVM: Which is an evaluation module for the TCS230. It consists of a board with TCS230, and a microcontroller.

Advantages:

There are two white LEDs placed beside the sensor for lightning the aria which is right under it.

Disadvantages:

1) It is expensive : about 150$.

2) BasicStamp programming envirument is not present in the lab.

Second option is the PIC DEM 2 PLUS :

This is a programming environment for PIC. It is available in the lab and is being used in other projects.

The PICDEM 2 Plus can be used stand-alone with a programmed part, with an in-circuit emulator

The programming of the PIC is done in a c-like language, this is better than programming in BasicStamp because it is a higher lever language.

Finally we will use this board.

In choosing the chips we considered the following:

•They all can operate at approximately low power supply,this is important for portability requirement.

•The micro controller I/O pin number, for controlling the light analyzer and the voice memory chips and to communicate with the voice memory…

•The protocol for communication between the micro controller and the voice memory.

•All the chips should be inexpensive.

Light Analyzer:

We chose the new TAOS TCS230 programmable color light to frequency converter since it is suitable to our goal. For each measurement the sensor’s only output is a square wave with frequency directly proportional to light intensity.

The light-to-frequency converter reads an 8 x 8 array of photodiodes. Sixteen photodiodes have blue filters, 16 photodiodes have green filters, 16 photodiodes have red filters, and 16 photodiodes are clear with no filters.

The result is that we can measure the intensity of the red, green and blue components of color.

Voice memory:

It is used to describe the color in a voice message to the user. We will use the Winbond ISD4002 chip which has enough memory and record/playback features.

The ISD4002 supports SPI protocol for communication with a micro controller.

Storing messages in the ISD is done in a circuit used for recording. This circuit includes also a micro controller and a microphone.

Micro controller:

We chose the PIC18F252 which has all the features we need, an interface to communicate with the other chips, enough memory, low power, etc… (see specifications section).

In addition, this micro controller is compatible with SPIProtocol.

TCS230

PIC18F252

ISD4002

Light Source

MicrophoneSpeaker

TAOS TCS230:

•A programmable color light-to-frequency converter

•Vdd = 5 V

•Idd = 2 mA (Power-on mode)

7 uA (Power-down mode)

MICROCHIP PIC18F252

•High Performance, Enhanced FLASH Microcontroller

•Vdd = 5 V

•Idd = 0.5 – 1.5 mA

•Supports SPI protocol

•Memory:Flash 32 KB

On-chip RAM 1536 B

Dat EEPROM 256 B

WINBOND ISD4002:

• Single-chip voice record/playback solution

• Vcc = 3 V

• Icc = 15 mA (Playback)

25 mA (Record)

• Isb = 1 uA (Standby)

• 120 seconds duration

• SPI interface

What have been already done:

•Searching the internet for info on color detection

•Choosing and ordering chips.

•Studying the datasheets.

•Whole system design.

•Building a test circuit for TCS230.

•Solving the sensitivity problem by moving the TCS into an optical mouse package.

Technical problems:

We haven’t received ISD4002 chip yet.

We were supposed to get our own PIC demonstration board, but there is no available one. Only next week we will start to share a board with another group.

There were two major problems in dealing with the TCS230 (the color sensor):•The TCS230 is very sensitive to the environment light condition, so it should receive the light that is only reflected from the object.

•Since it is very sensitive, we need a light source that is as stable as possible, and contains almost all the visible spectrum of the light.

The solutions that we have chosen are (we had already implemented):

•We are using the package of a PC optical mouse, since it is suitable to our purpose – we put the TCS230 instead of the mouse light sensor…

•We used a WHITE LED – it is the ultimate choice we have seen…

Period Project Process Comments

01.01 – 07.01

Working with PIC and it’s development environment + Finalizing testing of

TCS230

We are supposed to

get Env. Board this week

08.01-15.01

Programming the PIC for color detection with TCS230

16.01-23.01

Building a recording circuit for ISD + Programming it by the PIC

We did not get the ISD yet.

24.01-30.01

Integration

1.02- 24.02

Exams period

25.02- …

Debugging + Documentation Final report and presentation