Elenco Radio Controlled Car Soldering - Manual (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 active. 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 interference between this product and all other electrical products.
Characteristics of Radio Reception:
Many 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 transmits energy in all directions so as the range between 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 ~ 600
µ
s
spacing.
~ ~
Burst sequence, each ~ 600
µ
s long with
~ 600
µ
s spacing.
10 bursts for forward; 34 bursts for forward-left;
28 bursts for forward-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”.