Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. REMOTE CONTROL Overview In this lesson you...

Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.

REMOTE CONTROL Overview

In this lesson you will learn:

• The relationship between (RF)

transmitters and receivers

• Resonance—the underlying

scientific factor that allows the

precise transmission

frequency of a signal

• Engineering notation

Vex CONTROLLER AND RADIO

IMAGES HERE


REMOTE CONTROL Introduction

The kettledrum

If a trumpet and a kettledrum tuned to the note of “E” were placed

in the same room, when the trumpet played the “E” note the

sound wave would leave the trumpet and travel through the air.

The air molecules would then vibrate against the surface of the

drum and the drum would vibrate with an audible sound.


A dramatic example of resonance is

demonstrated by the Tacoma

Narrows Bridge disaster. Click

“Background/Slide Shows/Tacoma

Bridge: Example of Resonance” to

see the video.


What is resonance?

Resonance is the induction on a physical object of vibrations by a

vibrating force having the same frequency.



Glossary

Crystal An electronic device, such as an oscillator or detector, using

such a material.

Oscillator To oscillate means to swing back and forth with a steady,

uninterrupted rhythm. An oscillator is a device or

mechanism for producing or controlling oscillations;

especially:one (as a radiofrequency or audio-frequency

generator) for producing an alternating current



Resonance in electronic circuits

The induction on a physical object of vibrations by a vibrating force having

the same frequency.

The relationship between resonance and crystals is critical for this

exercise. The crystal placed in the transmitter is contained in a circuit

called an oscillator. The oscillator circuit then uses a concept called

feedback to send electrons to vibrate the crystal in the same manner

that the air molecules vibrated the kettledrum. This will cause the crystal to

vibrate at its resonance frequency and the oscillator circuit will send

a sinusoidal signal to an amplifier. The amplified signal will then travel

to an antenna where the electrical signal is changed to an electromagnetic

wave that will travel through the air.



Resonance in Vex

The Vex receiver circuit uses an antenna to receive all electromagnetic

waves in its vicinity changing these waves to an electrical signal. An

amplifier then amplifies the electric signal and is sent to a circuit

containing a crystal. If the amplified signal is at the same frequency of

the crystal, then the crystal circuit generates a large sinusoidal signal.

Upon the generation of this sinusoidal signal another circuit will be

initiated causing the motor to be activated.


Transmitter / Receiver Range

Horizontal Antenna Test

HORIZONTAL Antenna Test


Materials needed

Constructed robotic system

Radio transmitter

Yard stick

Tape measure

Range Table 1 data sheet


Step 1

Place robotic system at

stationary point. Turn on the Vex

Controller and Radio. Make sure

to have plenty of linear space for

this experiment.


Step 2

Place the radio in front of the

robotic system lying flat with the

back on the ground. Make sure

the antenna is extended 1 inch

for minimal reception.


Step 3

Start the experiment by pushing

the joystick of the radio forward.

With the radio on the ground

slowly slide it away from the test

assembly. Once the radio goes

out of range and the motor stops

slide it back until a consistent

connection is achieved.


Step 3 continued

When you find and maintain

a consistent signal, measure

the distance from the radio

to the antenna and record

it on Data Table 1.


Step 4

Using the yard stick,

extend the antenna 4” from the

radio and follow the same

procedure in step 3 to find a

consistent signal at maximum

distance, record the distance on

your data table.


Step 5

Next, extend the antenna

8” from the radio and follow the

same procedure as in Steps 3

and 4.


Step 6

Continue to extend the antenna

in 4” increments and measuring

the distance from antenna tip

to the receiver. Record the data

in the packet at each increment.

You will have 8 distances

recorded in Table 1.


Step 7

1. Complete graph comparison

data sheet, using the

“Example Data for Student

Exercises” as a guide.

2. Complete a reflection

worksheet.

ADD VISUALS FOR DATA SHEET AND

REFLECTION WORKSHEET


VERTICAL Antenna Test


Materials needed


Radio transmitter

Yard stick

Tape measure



Step 1

Place robotic system at a

stationary point. Turn on Vex

controller and radio.IMAGE OF CONTROLLER AND RADIO BEING TURNED ON


Step 2

Place radio in front of robotic

system upright and the antenna

pointing towards the ceiling.

Extend the antenna 1” to gain

minimal reception.


Step 3

Move the radio back slowly while

keeping it in a vertical position.

Once the motor stops slide it

back to find the farthest spot of

consistent connection. Measure

the distance back to the antenna

and record the data in table 2.


Step 4

Using the yard stick, extend the

antenna 4” from the radio and

follow the same procedure in

step 3. Once you find a

consistent signal at a maximum

distance, measure from the

antenna tip to the receiver

antenna. Record the data in

Table 2.


Step 5



same procedure. Record the

data in Table 2.


Step 6



the distance from antenna tip to

the receiver. Record the data in

the packet at each increment.




Step 7


data sheet, using “Example

Data for Student Exercises”

as a guide.


worksheet.




WAIST HIGH Test


Materials needed


Radio transmitter

Yard stick

Tape measure



Step 1

Place the radio in front of robotic

system, waist high

(approximately 2’ -3’), and the

antenna between 45 degrees

and vertical. Extract the antenna

to 1” to gain minimal reception.


Step 2

Start by pushing down the

joystick to start the motor. Slowly

back up with the radio at your

waist tilted at 45 degrees. Once

you find the greatest distance of

consistent communication record

it in data table 3.


Step 3

Using the yard stick, extend the

antenna 4” from the radio and

follow the same procedure in

step 3 to find a consistent signal.

Once you find a consistent

signal at a maximum distance,

measure from the antenna tip to

the receiver antenna. Record the

data in Table 3.


Step 4



same procedure in step 3 to find

a consistent signal. Once you

find a consistent signal at a

maximum distance, measure

from the antenna tip to the

receiver antenna. Record the

data in Table 3.


Step 5



same procedure in step 3 to find

a consistent signal. Once you

find a consistent signal at a

maximum distance, measure

from the antenna tip to the

receiver antenna. Record the

data in Table 2.


Step 6



the distance from antenna tip to

the receiver. Record the data

in the packet at each increment.




Step 7


Data Sheet, using “Example


as a guide.


worksheet.




TEST with Obstacles


Materials needed


Radio transmitter

Tape measure

Sheet of paper

Wood

Sheet metal

Range Table 2 Data sheet


Step 1

Place robotic system at a

stationary point. Turn on Vex

controller and radio.


Step 2

Place the radio in front of

robotic system, waist high

(approximately 2’ -3’),

and the antenna between 45

degrees and vertical. Make sure

antenna is fully extended from

the radio.


Step 3

Begin the experiment by placing

a piece of paper on top of the

receiver and the antenna. Make

sure the antenna wire is not in

the plastic tube and is wrapped

around the receiver. Push

forward on the joystick of the

radio to turn on the motor of the

robotic system.


Step 3 continued

Slowly walk backwards until the

motor stops. Find the maximum

distance of consistent

connection. Measure the

distance from the radio to the

antenna. Record the data in

Table 4.


Step 4

Next place a piece of wood over

the antenna where the paper

was previously. Repeat the

experiment and record the

results in data table 4.


Step 5

For the last test use a piece of

sheet metal in place of the wood

or paper. Repeat the experiment

as before and record the results

in data table 4.


Step 6


Data Sheet, using “Example


as a guide.


worksheet.



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