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Re: How to select a Tx/Rx for my robot?

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  • Terry Slocum
    The answers will depend a lot on your budget and what you plan to do with the robot. If you are serously interested and plan to stay with robotics for awhile.
    Message 1 of 3 , May 23 8:18 AM
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      The answers will depend a lot on your budget and what you plan to do
      with the robot.

      If you are serously interested and plan to stay with robotics for
      awhile. I would recommend getting a transmitter with more
      capabilities than you need right now. At least 3 proportional
      channels are needed if you want to ever have a combat robot with a
      motor driven weapon. Some RC car transmitters only give you on an off
      on the thrid channel, or are so slow to change the position on the
      third channel that it really isn't usable. You can use a good
      transmitter over and over with each new designs, so don't skimpt to
      much here.

      For large competitions the new Spektrum system is the way to go. You
      will avoid the problem of not being able to test properly because you
      don't always have access to the frequency. This usually isn't a big
      issue at smaller events.

      To save money you may be able to pick up a used transmitter from
      someone. A lot of people are trading up to the spektrum radios. I
      have a couple myself.

      If you are talking about a combat robot, most people use off the
      shelf controllers for the motors. Many of them have the ability to
      convert RC Servo PWM built in. In the insect classes you may be able
      to find a controller with a weapons channel that can drive your
      solenoid.

      Tell us a little more about what you are doing and we may be able to
      give you some specific suggestions.

      Hope this helps.

      Terry


      --- In sfrsa@yahoogroups.com, "marble_kid" <bgracia1@...> wrote:
      >
      > I am just getting started designing my first robot. I need help
      > selecting the Tx/Rx. I have never used or been around these, so I
      am
      > not exactly sure what I should be looking for.
      >
      > My robot will be both powered and steered by the rear wheels, so
      there
      > will be two separate motors. I also will have one other function,
      I
      > need to control a pull type silenoid to release a cable.
      >
      > I am thinking 3 channel Tx/Rx. If this is the case, then when I
      get
      > the Rx, how do I access the signals. I believe they will be PWM
      and if
      > this is the case, then a PIC can read and convert the signals for
      me.
      >
      > Are there any docs, hints, lessons on using a Tx/Rx setup on the
      net
      > for me to look at?
      >
      > Thanks,
      > Brian G.
      >
    • Camp Peavy
      ESCs (Electronic Speed Controls) as used with RC cars and planes allow you to control DC motors with your radio radio (back, forth and stop). You are basically
      Message 2 of 3 , May 23 1:45 PM
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        ESCs (Electronic Speed Controls) as used with RC cars and planes allow you to control DC motors with your radio radio (back, forth and stop). You are basically pulsing these between 1 and 2 milliseconds for clockwise/counterclockwise and 1.5ms for stop. This is how you would control them with your microcontroller as well (pulse them). An ESC allows you to treat DC motors like servos. You would need two; one for each wheel. I'm using the Novak XRS on my robots http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGNG5&P=ML
         
        Careful! High-end RC car ESC's are generally limited to forward as reverse is not allowed in RC car racing. Get the "Sport" version which usually implies reverse... also in general you need to stop the ESC (1.5ms) before reversing direction. Most commercial versions expect the user to go forward, hit the brake (reverse throttle) and then go back to the neutral position and reverse throttle again to actually backup... this protects the MOSFETs. The microcontoller would simply need to have a subroutine that stopped the motor before reversing direction. An ESC could be used to actuate the solenoid as well.
         
        Good luck,
        Camp
         
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