URGENT!!!

Discussion in 'Homework Help' started by solar powered, Apr 29, 2009.

  1. solar powered

    Thread Starter New Member

    Apr 29, 2009
    3
    0
    hi all, i am designing a set of two solar powered wireless traffic light, i would like to know that how can Programmable Logic controller be connected to a radio frequency that can allow one traffic light to turn green and the other to turn red without using any wires to communicate.
     
  2. steinar96

    Active Member

    Apr 18, 2009
    239
    4
    You need to be alot more specific if you want answers. And your solution of wireless communication might be quite complex and could easily require multiple IC's and circuitry to function. Which means that before anyone could even post a circuit diagram for you he would need alot of information regarding this project of yours :)
     
  3. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    I see the practical use for radio in order to save on copper and avoid overhead circuitry. The light would require a radio receiver and the little box that controls it would need a transmitter. There are many ways to do this.
     
  4. etuzuner

    Member

    Mar 21, 2009
    23
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    As it was told, if you can tell the details, I'm sure that you will be helped.

    By the way, there are a lot of things that you can do with PLC. More generally, you can control anything that works with electricity..:)(Assuming transformerd energy and suitable values for the specification of the PLC)

    Regards
     
  5. solar powered

    Thread Starter New Member

    Apr 29, 2009
    3
    0
    The traffic lights are meant for roadwork purposes. The two traffic lights will be placed at the start and end of the roadwork. Each traffic light will have the "STOP" and "GO" sign. They have to be solar powered and be able to communicate wireless with each other.

    When one traffic light has "STOP" sign on, the other traffic light will have the "GO" sign on. We are thinking of using LEDs.

    We are also thinking of using PLC to programme the traffic light, the thing is we dunno how to incorporate the wireless thing into the traffic lights. Do we connect it to the PLC? If so, how do we connect it and how do we operate the traffic lights? It has to change the lights automatically.

    Thanks..
     
  6. steinar96

    Active Member

    Apr 18, 2009
    239
    4
    If you intend to use a PLC you'd propably use it to keep track of the state the light is in.
    Building the wireless device to output a HIGH signal on one of the PLC's input ports would enable you to detect when a signal is recieved and switch the state.
    Thus if it were in the STOP state it'd switch to the GO stage once the input port went high due to the wireless circuitry recieving the signal.

    Since you have 2 traffic light's you could designate one of them as a controller (master/slave configuration). So each time the master light switched state it would output a signal recieved by the other one which would switch it's state. Thus they should always be in a seperate state as long as they begin in a seperate state.

    Controlling the master can be done in many ways, by timing or remotely by yourself for example.

    Maybe this can get you going.
     
  7. etuzuner

    Member

    Mar 21, 2009
    23
    0
    That's depend on how you want to do it. The bit rate, probability of error, range etc. are the variables that you decide as you know. After these, you use PLC as a switch, hypothetically. You tell PLC to activate y1 "X" seconds. After "X" seconds, cut off y1 and turn on y2. You put these statements to a loop which continues till you activate the input, let's say x1. When x1 is on, the loop is terminated.

    If I couldn't tell exactly what I meant, please let me know. I may give you the ladder diagram in a few days.

    Regards
     
  8. PRS

    Well-Known Member

    Aug 24, 2008
    989
    35
    Why use PLC to program the light? As you described it, there are only two states: red and green. Just have a clock pulse a flip flop to high and low. High might be green, low red.

    As for the radio circuit just send a sinewave over an antenna. It's presence means green, absence means red. The sinewave can be detected with a diode and a resistor.
     
  9. steinar96

    Active Member

    Apr 18, 2009
    239
    4
    yeah i'll have to agree with PRS. Using a PLC is propably more work then needed for the project. Easier and cheaper to implement with a flip-flop.
     
  10. solar powered

    Thread Starter New Member

    Apr 29, 2009
    3
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    That is very kind of you, etuzuner. What is a flip flop exactly? I dunno really know all these terms, so sorry. How abt using a micro controller? P18f4520.h

    I think we may have to incoporate sensors into the traffic lights now, to sense when there are cars and make the traffic light more "intelligent".

    We can't have the light change from red to green immediately as there may be cars still passing through in the middle of the road and they cant stop immeditately. Whereas the cars from the other side cant pass if the cars from the other side stop immediately. That is why we are thiking of using a sensor.

    I am having problems programming the traffic lights using the P18f4520.h now...........
     
  11. Tristy-Poo

    New Member

    Feb 12, 2008
    4
    0
    hi solar powered

    if your new to using micro controllers then i recommend starting with a picaxe (http://www.rev-ed.co.uk/picaxe/) , they are very easy to program and the code is simple. schools and colleges use them for projects just like you need to create. i'v been using them since i was 17 just for hobby stuff really.

    i think you would then need to hook it up to an RF transmitter and another picaxe to the reciever. a small 433mhz (100m range) transmitter and reciever should cost around £10. around $17

    good luck
     
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