Elenco Electronics RCC-7K Guide de dépannage télécharger pdf (Page 4)

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THEORY OF OPERATION

Remote Control Transmitter: (refer to the schematics and block diagram on p.31 as needed)

When the levers in the Remote Control Unit are pushed electrical contacts are made connecting the 9V battery

power to the transmitter and indicating which commands the user wants sent to the car. Forwards/Backwards

and Left/Right commands are controlled by different levers and use different sets of electrical contacts that are

used to encode a sequence of electrical pulses; the number of pulses depends on which command is being

sent. On some models Left/Right commands are only sent if Forwards/Backwards commands are also being

sent, since there is too much friction to turn the wheels unless the car is moving.

An electrical circuit that is tuned to a frequency of 27.9MHz creates a signal that is sent to the antenna when

the pulses are activ

e. The antenna converts this electrical energy into radio energy, creating a stream of radio

energy bursts, which travel through the air to be picked up by and understood by the radio receiver in the car.

The frequency of 27.9MHz was selected for RCC-7K with the approval of the FCC (the US government) to

minimize radio interf

erence between this product and all other electrical products.

Characteristics of Radio Reception:

Man

y factors affect the ability of the RCC-7K to receive commands from its Remote Control Transmitter. A weak

battery in the Transmitter will result in a weaker transmitted signal; if the battery is very weak then the Transmitter

may not function at all. The Transmitter’s ability to convert electrical energy to radio energy is best when its

antenna is fully extended and degrades as the antenna length is reduced; the same thing also applies to the car

antenna’s ability to convert the radio signal back into electrical energy for the receiver. The Transmitter’s

antenna tr

ansmits energy in all directions so as the r

ange betw

een it and the car is increased less energy is

received at the car. When operated with strong batteries and in an open area the range will be at least 40 ft.

Obstacles such as walls, furniture, and trees will degrade the radio signal’s ability to travel through air and

reduce operating range, but will never block it completely. In some cases more radio energy may travel from

the Transmitter to the car by going around obstacles than by going through them. In the car, weak batteries will

{

Pulse Sequence

27.9MHz Signal

Transmitted Signal

4 synchronization bursts each

~ 1.8ms long with ~ 600µs

spacing.

Burst sequence, each ~ 600µs long with

~ 600µs spacing.

10 bursts for forward; 34 bursts for forward-left;

28 b

ursts f

or f

orward-right; 40 bursts for backward;

46 bursts for backward-left; 52 bursts for backward-right.

Note: some models use different sequence lengths

Sequence

Repeats

•

•••

•

•••

•

•••

Transmit Signals

INTRODUCTION

The RCC-7K is a radio-controlled car that you put together. It has 7 control functions: forward, forward-left,

forward-right, backward, backward-left, backward-right, and stop. The remote control operates at a frequency

of 27.9MHz. It uses 4 AA batteries and one 9V battery (not included). It takes about 7 hours to build.

Assembly of the RCC-7K will prove to be an exciting project and give much satisfaction and personal

achievement. If you have experience in soldering and wiring technique, you should have no problems. For the

beginner, care must be taken in identifying the proper components and in good soldering habits. Above all, take

your time and follow the easy step-by-step instructions. Remember, “An ounce of prevention is worth a pound

of cure”.

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Elenco Electronics RCC-7K Guide de dépannage Page 4

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