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Radio Controlled Switch being interferred with from BBQ Iqnitor

  1. Mar 19, 2010 #1
    Hello All,

    For a hobby, my father, friend, and I are building a radio controlled tank. Without getting into to much ancillory info, the problem we are facing appears to be radio frequency interference.

    Using a radio control transmitter, we are sending a signal to the receiver. That receiver in turn sends information to a switch (specifically a BattleSwitch http://www.dimensionengineering.com/BattleSwitch.htm). That switch completes a circuit to a BBQ pit electric ignitor. We have zero problem with this setup up to this point. The problem occurs after the ignitor starts firing. When that occurs, the other battle switches that we have also connected to the receiver start switching, even though we sent no signal to them from the radio transmitter. When these other switches start operating on their own, we obvious have problems with our system. To attempt to counteract this interferrence, we've tried wrapping the ignitor in aluminum foil as well as thin copper to shield the switches from what we think is causing the source of the stray RF. This has not fixed the problem. My latest theory is that the RF is somehow travelling down the control wire from the ignitor back to the battleswitch, back to the receiver, and then over to the other switches. I'm not the greatest with electricity and RF, but am stuck at this point.

    Please feel free to speculate or offer any solutions, we're up for trying anything at this point. Also if more info is needed, ask away as this might not be completely clear.

    From a fun perspective, we've recently taking some video of our "little" contraption and will soon be posting to youtube. It's pretty cool.

    Anyways, thanks in advance for any help/assistance.
     
  2. jcsd
  3. Mar 19, 2010 #2
    While your theory may be true, it is also possible the interference is originating with the Battleswitch. If you disconnect the igniter from the Battleswitch do the other channels still activate? If you disconnect the Battleswitch from the receiver, do you still have the problem?

    Do you know what frequency your radio control is using?
     
  4. Mar 19, 2010 #3
    no problems occur unless the ignitor is firing. when the ignitor is not firing, the other battleswitches work just fine and do not trigger on their own. There are 4 battleswitches on our control board, all connected to the receiver. Any battle switch being activated does not cause any of the other battle switches to trigger. Only one battle switch is currently connected to the ignitor. When another battle switch was swapped in for the ignitor, the same situation occurred.

    As for frequency, I'm 90% sure it's 2.4GHz. Its a very new digital model of airplane radio. We chose this type so that it would have 8+ channels for the different things we needed it to do.
     
  5. Mar 19, 2010 #4

    dlgoff

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    I'm thinking that the igniters circuit is generating noise. To get the high voltage, there's probably an oscillator; causing some EM radiation.
     
  6. Mar 19, 2010 #5
    You know, whenever someone is bugging with an electronics question and I have no idea what they're talking about, I always tell them that they need a huge capacitor. Having said that, you need a huge capacitor.

    The ignitior is a spark generator right? When you make a spark, you generate all kinds of noise. Think of it like hitting a metal pipe with a wrench. The strike is like the spark and the vibrations will travel all around the plumbing that is connected to the pipe. In your case, the electrical noise is traveling through the circuit to the logic gates and making them switch.

    What you need to do is isolate the sparker all by itself. A capacitor will provide a low impedance path for oscillations. The bigger the capacitor is, the lower it's impedance will be for a given frequency. A big enough capacitor with essentially provide a short circuit to any noise. This is called a bypass capacitor.

    The sparker has a power supply and a control line right? Make a dedicated ground line that connects to the sparker and only to the sparker. Put a 1 uF cap across the power supply and the dedicated ground and also any control line and dedicated ground. Hopefully, that will short-circuit the noise.
     
  7. Mar 22, 2010 #6
    You might try using a twisted pair of wires from the Battleswitch to the igniter and wrapping and taping aluminum foil around them. Connect the aluminum foil to the neutral side (be sure it's the neutral side) of the twisted pair at the Battleswitch. If it works or at least improves, you can probably find shielded twisted cable from a cable supply store. Be sure the cable is rated for the voltage at which it will be used.
     
  8. Mar 23, 2010 #7

    sophiecentaur

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    How many times a day do you need to light your BBQ?
    Is the interference significant?
    Or is someone using the BBQ igniter to jam your battlefield communications?

    You may have a resonant structure somewhere in your BBQ, which happens to tune your spark energy at your comms frequency. Have you tried another channel?
     
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