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Thread: RC toy car help...

  1. #1

    Default RC toy car help...

    heyya ... i wanna create a rc toy car.... m in ma 6th sem right now.. doing ece... i kinda understood the basics of the toy car....

    it shud basically contain the following stuff..
    Transmitter - You hold the transmitter in your hands to control the toy. It sends Radio waves to the receiver.
    Receiver - An antenna and circuit board inside the toy receives signals from the transmitter and activates motors inside the toy as commanded by the transmitter.
    Motor(s) - Motors can turn wheels, steer the vehicle, operate propellers, etc.
    Power source

    The transmitter sends a control signal to the receiver using radio waves , which then drives a motor, causing a specific action to occur. The motor in a car may cause the wheels to turn.The transmitter sends a signal over a frequency to the receiver in the toy. The transmitter has a power source, usually a 9-volt battery, that provides the power for the controls and transmission of the signal.Most RC toys operate at either 27 MHz or 49 MHz. Transmitters range from single-function simple controllers to full-function controllers with a wide range of options. An example of a single-function controller is one that makes the toy go forward when the trigger is pressed and backward when it is released. To stop the toy, you have to actually turn it off.

    Most full-function controllers have six controls:
    Forward
    Reverse
    Forward and Left
    Forward and Right
    Reverse and Left
    Reverse and Right
    In most full-function controllers, not pressing any buttons or turning any knobs causes the toy to stop and await further commands. Controllers for more advanced RC systems often use dual joysticks with several levels of response for precise control.

    We will assume that the exact frequency used is 27.9 MHz. Here's the sequence of events that take place when you use the RC transmitter:
    You press a trigger to make the truck go forward.

    The trigger causes a pair of electrical contacts to touch, completing a circuit connected to a specific pin of an integrated circuit (IC).

    The completed circuit causes the transmitter to transmit a set sequence of electrical pulses (see How Radio Works for details).

    Each sequence contains a short group of synchronization pulses, followed by the pulse sequence. For our truck, the synchronization segment -- which alerts the receiver to incoming information -- is four pulses that are 2.1 milliseconds (thousandths of a second) long, with 700-microsecond (millionths of a second) intervals. The pulse segment, which tells the antenna what the new information is, uses 700-microsecond pulses with 700-microsecond intervals.

    heres the image ...
    http://static.howstuffworks.com/gif/rc-toy-pulse.gif
    http://static.howstuffworks.com/gif/...lse-labels.gif

    Here are the pulse sequences used in the pulse segment:
    Forward: 16 pulses
    Reverse: 40 pulses
    Forward/Left: 28 pulses
    Forward/Right: 34 pulses
    Reverse/Left: 52 pulses
    Reverse/Right: 46 pulses

    The transmitter sends bursts of radio waves that oscillate with a frequency of 27,900,000 cycles per second (27.9 MHz). If you have read How Radio Works, you will recognize this as pulse modulation.

    The truck is constantly monitoring the assigned frequency (27.9 MHz) for a signal. When the receiver receives the radio bursts from the transmitter, it sends the signal to a filter that blocks out any signals picked up by the antenna other than 27.9 MHz. The remaining signal is converted back into an electrical pulse sequence.

    The pulse sequence is sent to the IC in the truck, which decodes the sequence and starts the appropriate motor. For our example, the pulse sequence is 16 pulses (forward), which means that the IC sends positive current to the motor running the wheels. If the next pulse sequence were 40 pulses (reverse), the IC would invert the current to the same motor to make it spin in the opposite direction.

    The motor's shaft actually has a gear on the end of it, instead of connecting directly to the axle. This decreases the motor's speed but increases the torque, giving the truck adequate power through the use of a small electric motor!

    The truck moves forward.

    inside the truck ...
    http://static.howstuffworks.com/gif/...uck-inside.jpg

    One motor turns the front wheel right or left, while the other motor turns the rear wheels to go forward or backward. The circuit board contains the IC chip, amplifier and radio receiver. A few simple gears connect the motors to the wheels.

    i got the above info by surfing the net n mainly from howstuffworks.com .... i understood every bit of it ... but i dunno where to start from when it comes to building it.. i have the following queries ...

    a) Is there a seperate module(IC) available out there for transmitting pulses in the transmitting section ... n a receiever module(IC) for receiving the pulse...
    b) If so how do i assign the pulses leng required for the decoder IC to know if the pulse length specifies a fwd or reverse motion... ???
    c) besides a filter ... decoder ... amplifier n a receiving module(IC) for the receiever section what else is required?

  2. #2

    Default

    make it some simple yaar!!!!!

  3. #3

    Default

    Quote Originally Posted by hardikcool
    make it some simple yaar!!!!!
    i thot the above one was simple enough ... ne suggestions on how to make it more simple ??? u mean using a microcontroller ? instead of the discrete components ??? :?:

  4. #4
    Senior Member Cyborg
    Join Date
    Apr 2007
    Location
    Mumbai
    Posts
    213

    Default

    Is it RFQ or project?
    Project is somthing which you have to do yourself and ask if there is a problem.

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