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One battery, four circuits

Discussion in 'General Electronics Discussion' started by Matthew Klick, May 5, 2018.

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  1. Matthew Klick

    Matthew Klick

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    May 5, 2018
    I'm trying to build a model rocket launch controller. This will have to be powered by a single source but be able to handle four launches, independently, at once.

    I can build a single launch controller. My problem is that I've never tried running multiple circuits on one power source before. Can I just use a diode to keep the current from feeding back into another circuit or... I'm just not sure.

    Any thoughts would be most helpful.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Just run separate power connections from each controller back to the power supply.

    Make sure the power supply can handle it if all 4 are operated simultaneously.

    Or are you talking about 4 controllers in one box? In that case run the power to the box and split off the 4 power connections in the box.

    Or... Are you talking about one controller firing 4 separate rockets simultaneously? This may be a little more difficult because the controller may be only rated to fire one. Placing several loss in parallel may overload it and/or be unreliable.

    Which one is it?
     
    Last edited: May 5, 2018
  3. Matthew Klick

    Matthew Klick

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    May 5, 2018
    If every rocket is fired at once, it'll pull about 28 amps for a split second. Once a rocket ignites the circuit is broken. The battery I'm using will easily be able to handle that.

    The way I need to set it up is, a single battery will run to a switch to turn the whole system on and off. After that switch I want to split the power between the four launch controllers.

    Each controller will have a SPDT key switch. In the first position: key switch > resistor > LED > rocket > common negative. This is to check for continuity before launch.

    In the second position: key switch > momentary switch > rocket > common negative. This is to dump whatever it can into the rocket to launch it.

    I know running these circuits in series won't work for obvious reasons. I'm a little confused about whether or not it'll work in parallel or if there's anything special I have to do to make it work.

    This whole thing has to be one unit otherwise there's no point. There can only be one power supply because it's a single 70 year old woman that has to carry this out into a field. And it has to be able to launch all rockets at once or one at a time, because it'll be kids hitting the launch button.
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    In that case, it sounds like you have a battery and a switch in one box, with 4 cables, each one running from one end of the battery and the switch to each of the controllers.

    Make sure the power switch can handle 28A.
     
  5. Matthew Klick

    Matthew Klick

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    May 5, 2018
    That's correct. I'm guessing that setting it up in such a way will allow each circuit to operate as they would independently, and I just have to be sure that the battery can handle the load of all four circuits combined.

    Am I correct?
    Given that this is for launching rockets, I wanted to check with someone more knowledgeable than myself before I tried it.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Yeah, connecting them in parallel is how you achieve your aims.

    You probably should have a 15A fuse on each of the separate circuits for the controllers in case one of them shorts out.
     
    Cannonball likes this.
  7. Matthew Klick

    Matthew Klick

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    May 5, 2018
    Ah, I thank you sir! I've actually played with electronics quite a bit in my day. Something about rockets controlled by 12 year old kids makes me want to get second opinions. lol
     
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