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Help about transmitter and receiver

Discussion in 'General Electronics Discussion' started by assuc, Dec 20, 2011.

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  1. assuc

    assuc

    12
    0
    Dec 20, 2011
    Assalam o alaikum,
    I am Asad Jabbar and recently joined this forum. I am in the 2nd semester of engineering and want some serious help.

    Actually i am using a relay driver circuit to drive a dc motor at 7.4v and 2 ampere. The problem is that when i connect the output of receiver i.e., signal wire and ground wire on the circuit and try to run the motor it doesn't work but as instead when i am not using the receiver output and giving direct power with a 5v battery the relay driver circuit is working fine.
    Now i want you guys to help me solve the issue to use my receiver output to drive the relay circuit when i use the signals from it.

    Note: I am using 2.4ghz esky transmitter receiver. The voltage of signal-ground at static is 0.22v. When i forward the throttle stick it gives 0.28v and at reversing the throttle it gives 0.18v. one more thing the futaba servo is working fine with it.

    Relay Driver Circuit
    Untitled.png

    Regards
     
  2. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
  3. assuc

    assuc

    12
    0
    Dec 20, 2011
    Thank You for your great reply.
    Another thing i want to ask that can we measure the ppm?
    And what i learned from the links you provided is that i should add a ppm conversion part hence a servo amplifier, correct me if i am wrong and please do explain it.
    Regards,
    Asad
     
  4. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Asad,

    You already "measure" the PPM as the voltages values you give in your first post are averaged values of the pulses (the wider the pulse the higher the voltage).
    More precises measurements needs a scope.

    If you want to control the motor in both directions, especially with relays, you can't
    implement a servo amplifier as it. However solution's exist to control the relays with two channels (as you try) or even one. Mean convert a pulse in something able to control the transistor base.
    As you have the honesty to clearly state that you are a student, I let you suggest how it can be done.

    Olivier
     
  5. assuc

    assuc

    12
    0
    Dec 20, 2011
    Oliver,
    The same statement was given to me from one of my senior fellow to control both relays individually. But the thing he told me that your ppm from receiver is very low if it could be higher like 1.5v static,forward 2v and reverse 1 v then it will be implemented on the relay driver circuit.
    One more solution he suggested me is to use the micro-controller at the least to control the motor in both the direction.
    You have also provided me the same thing to control relay individually with 2 channel.
    But I wonder how the RC cars that are in the market are controlled by same channel means same throttle stick(if they forward it the car moves forward and with the same channel they move the throttle to reverse it goes reverse). If you have any idea regarding it then do tell me or at last i am of the opinion to install micro-controller

    Regards
    Asad
     
  6. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    Asad,

    The means are almost the same to drive a relay from a pulse from one or 2 channels. You already find out that you can have the pulse width value being converter to a voltage.

    So an analog solution can be to integrate the pulse and amplify it to around 5 volts.
    A digital solution (close to what you can implement on a µc) is to trig a circuit output when let say 1.2 mS is elapsed.

    Despite this kind of receiver to relay interface will be OK they are caveats on "system" level (Transmitter+receiver+interface+relays+motor) . Your senior fellow as certainly anticipated that and it's probably why he suggest you the µc solution as it will make things more versatile and more future proof.

    However better to keep in mind that basic things like convert a pulse to something else (and even solve the caveat I talk you about) can be done without any µc !

    The marketed RC cars, the one channel solution so, just distinguish the pulse width.

    example:

    Under 1.3mS they go forward
    around 1.5mS they stop
    Above 1.7ms they go reverse

    Olivier
     
  7. assuc

    assuc

    12
    0
    Dec 20, 2011
    Oliver,

    The same thing is i am searching of that what could be the possible components used to make that pulse trigger to such voltage that my relay driver ckt works as that what is being done in the micro-controller.
    As for the RC cars the scenario you explained is the same as i thought when the first time i built up this ckt.
    Anyways thanks for the keen suggestions and help. I'll try to get to a solution sooner or later and in case if you reach any solution then do share!

    Regards
     
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