Sonar Sensor Project Polaroid Sonar Sensor Measuring Distance with Sound Waves Overview of the...

Sonar Sensor Project Polaroid Sonar Sensor

Measuring Distance with Sound Waves Overview of the Sensor Module

Details of the Project Sonar Circuit and Processor Concept of Handshaking Sensor and Processor FSMs Calculation of Velocity

ECE 3450 M. A. Jupina, VU, 2013

Particulars of the Sonar Sensor

• Range is six inches to 35 feet

• 16 cycles at 49Khz

• Listen for return pattern

• Sound travels ~0.9 ms/ft

• Timer on DE2 determines distance

Transducer Transmitter/Receiver


Ultrasonic Transducer and Circuitry

Sound waves above the audio range (20 Hz – 20 KHz) are transmitted and received by the sensor so as to ascertain thelocation of an object.


Speed of Sound

Sound waves travel at

330 meters-per-second or

1082 feet-per-second or

1.082 feet-per-millisecond or

~0.9 millisecond-per-foot.


Using Sound Waves to Measure Distance

SensorObject

X

The transmitted and reflected sound waves travel a total distance 2X.

Therefore, total travel time = (0.9ms/ft)(2X)


Polaroid 6500 Sonar Ranging Module


Circuit Diagram

Tra

nsdu

cer


Schematic Equivalent Circuits of Polaroid Module’s Inputs and Outputs

The echo output is an open collector transistor output and requires a 4.7 K pull-up resistor between VCC and the output.


Ultrasonic Source/Detector


Detector Sensitivity versus Frequency

Polaroid detector has a maximum sensitivity at ~50 KHz.


Ultrasonic Detection – Highly Directional

Transducer

Object

At 0o : detected signal = -3dB = 0.5 source signal At 30o : detected signal = -20dB = 0.01 source signal

Transducer

Side Lobes

2Vsin D DF

Main Beam


Sonar Sensor SignalsPower is turned-on

External Trigger

16 cycles at 49.4 KHzsent by the transducer

Control lines tied low

Detector turned-off

Transducer receivesreflected signal

Measurement range is six inches (due to internal blanking) to 35 feet (due to sensitivity)

Data Request Signal

Data Ready Signal

Total Travel Time

~0.02ms 1/2E-5 = 50 KHz


System Diagram

SonarCircuit

4-bits

DATA

Data Request

Data Ready

PROCESSOR SONAR SYSTEM

Data BusRegisters

ALU

FSMs


“Handshaking” Signals

• When the Processor requires new data, it raises the Data Request line high (to “1” ).

• Once the Sonar System sees this and has placed the correct data on the 4-bit Data lines, it raises the Data Ready line high.

• When the Processor has taken the data (typically stored in a D-register) it lowers the Data Request line.

• After this, the Sonar System lowers the Data Ready line.• The Processor can only issue a new request after the Data

Ready line is lowered. ECE 3450 M. A. Jupina, VU, 2013

Sonar Project Circuit

?

Clock_50MHz


The Sonar Counter Circuit

• The sonar module can be trigger (or initialized) up to 10 times every second (We will only trigger it once a second so a 1 Hz square wave will be used).

• A counter is used to measure the total travel time of the sound wave. The counter measures the time (actually the number of clock cycles) between the rising edge of the INIT or Data Request signal and the rising edge of the ECHO or Data Ready signal.

• The rising edge of Data Request signal triggers the counter to begin counting and the rising edge of the Data Ready signal triggers the registers in the counter block to store the count.


Sonar Circuit Block

8-bitCounter

Divide by16

8-bits

CLOCK Cycles

4-bits

Position in feet

What is the system clock frequency if 54 clock cycles are to represent a measured distance of 3 feet?


Position Measurement

• The Sonar Count is divided down to a number to represent the position in feet. The position is updated once every second.

• The position of a person standing 2 to 7 feet away from the sonar sensor will be sensed.


SONARCIRCUIT.BDF


SONARCOUNT.VHD


Sonar Count Simulation


LPM_CLSHIFT


LPM_CLSHIFT

Parameters


SONARCIRCUIT.BDF

VCCOr

GND


Sonar Circuit Simulation


PROCESSOR Block


PROCESSOR.BDF

Register A: Current PositionRegister B: Current VelocityRegister C: Previous PositionRegA – RegC: Calculates Velocity


SENSORFSM.VHD


SENSORFSM.VHD Con’t


SENSOR FSM Simulation


PROCFSM.VHD


PROCFSM.VHD Con’t


PROCESSOR FSM Simulation


Sonar Project File for Simulation(SONARPROJECT1.BDF)


Velocity Measurement

The magnitude of a person’s velocity in feet-per-second is determined by a subtraction circuit in the processor block and an absolute value circuit (lpm_abs block). The magnitude of the velocity is updated once every second.


SONARPROJECT1.BDF


SONARPROJECT1.VWF


Sonar Project File for Testing(SONARPROJECT2.BDF)

SystemClockFrequency ?

Signals to & from Sensor:INIT – PIN_D25ECHO – PIN_J22

?

? ?

?Clock_50MHz


Pin Assignments for DE2 Board

1. Reset is PIN_N252. 50 MHz clock is PIN_N23. INIT is PIN_D25 (Pin 1 on JP1)4. ECHO is PIN_J22 (Pin 2 on JP1)5. Common Ground is Pin 12 on JP16. Seven Segment Displays are …


Clock Inputs


Header Pin Assignments


Sonar Project Pre-Lab Assignment

1) Determine the system clock frequency such that 54 clock cycles represent a measured distance of 3 feet by the sonar sensor. Use this frequency to set up the SYSCLK signal in the SONARCIRCUIT.VWF waveform file.

2) Determine the state diagram and table of the SENSOR FSM.

3) Determine the state diagram and table and finish the VHDL Code in the procfsm.vhd file so that the following sequence of events can be performed in the Processor Block:

a) Load the “current” position data into register A.

b) Calculate the velocity by performing the following subtraction: RA–RC.

c) Load the velocity data into register B.

d) Load the “previous” position data into register C.


Sonar Sensor Practicum WorkWork to be preformed in the Lab:1) Set up the SONARCIRCUIT.BDF file. Properly

configure the LPM_CLSHIFT block. Create a ModelSim simulation and verify the SONAR Circuit.

2) Set up the PROCESSOR.BDF file; save and compile it.

3) Set up the SONARPROJECT1.BDF file; save, compile, and simulate it by using ModelSim.

4) Set up, save, and compile the SONARPROJECT2.BDF file for testing at a sensor station in the lab.


Design Verification at the Sensor Test Station1. Bring your laptop to the sensor test station.2. Start the Altera QUARTUS II software.3. Go to PROGRAMMER and add your

SONARPROJECT2.SOF file.4. Test your design by walking back and forth two to

seven feet in front of the sensor. What happens at 8 feet from the sensor?

5. Have either the instructor or TA verify the operation of your sonar sensor design.

6. Hand-in a print-out of the SONARPROJECT2.BDF file.


Design Project: “Sonic Tape Measure” 1. Design and implement a sonic sensor system

that measures distances in the units of either centimeters or inches at distances greater than ~2 feet from the sensor and calculates velocities in units of cm/s or inch/s. Your system must be able to measure the distance of an object from the sensor at least 10 feet away within 1 inch or 3 cm of accuracy.


Design Project: “Sonic Tape Measure” 2. You will need to increase the word size (> 4 bits) in

the processor block. You are to redesign the sonar circuit block in the prior sonar sensor project example. You can change the system clock frequency (see the note below and the following slide), the divider circuit, the counter circuit, etc to achieve your new system implementation. The seven segment displays can be used in whatever fashion you would like to display the distance measured and the calculated velocity. For example, the seven segment displays can display a base 10 or hex value indicating the total inches or centimeters measured, or the one seven segment display can indicate feet (in hex) and the second display can indicate inches (in hex).


Divide-by-35 Circuit to Generate a 720 KHz Signal


Design Project Deliverables 1. Each group will hand-in a design proposal (due date

TBA). In the design proposal (60% of the project grade), document all possible designs considered and then the final design (state why this design was chosen). Also, document contributions from each team member.

2. Each group will simulate their design to demonstrate functionality. Each group will demonstrate their design to the course instructor at the sensor test station (40% of the project grade). What is your measurement accuracy?


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