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36v 7a class D bicycle trailer system... amps & capacitors?

Discussion in 'General Electronics Discussion' started by budget minded, May 13, 2016.

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  1. budget minded

    budget minded

    3
    0
    May 13, 2016
    i'm looking to build a 36v bicycle trailer system using a pair of 96dB efficient 8" two ways as mains, and 4 x 12" subs i've calculated to have the highest output at 20Hz. i plan on using 3 smaller 12v 7a batteries and WANTED to add a capacitor as a buffer, but the cheapest high capacity caps i could find (eg. 1 farad +) are car audio caps, but none of those are rated for 36v even though the system i'm planning is just 7 amps. any ideas on how i could buffer the power supply with caps? run 3 car caps in parallel in the circuit to "re-divide 36v back into 12v" in essence? i would have thought a 1 farad capacitor should be more than enough for such a low amperage system.

    what would you say, too, is the maximum wattage i should be using with this system? i originally planned on using a 2x100wpc amp for my mains and a 1x200w amp for the subs, but now am thinking of using a 1x400w amp rated 15-44v with an optimum 9.8a power supply.

    i'm not well versed in circuit design at all, and at least as far as the amps go, would just say "fine... 2x100 + 1x400 shouldn't be a problem as it's close to each amp's ratings & class D is twice as efficient as A/B". my ignorance proved to be an issue when i started trying to build a 12v system a few years back, so i'd appreciate some feedback from people who understand electronic circuits better than i do.

    would i "side tap" each amp to charge them individually at 12v? i would think that once the circuit is broken by a switch, any batteries connected to either terminal make no difference when another circuit is created at each battery's terminals.

    one other thing, if i'm running a 36v series system, can't i side tap one of the batteries for a separate low power 12v circuit like driving an electronic EQ/crossover or LED lighting system?

    any help clarifying what i'm doing right or wrong with this design is appreciated.
     
    Last edited: May 13, 2016
  2. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    I have a strong moral objection to your project. The last thing I want, when riding on a pleasant bicycle trail is some idiot blasting his favorite music to detriment of everyone trying to enjoy a quiet trip away from such nonsense.

    Bob
     
  3. Alec_t

    Alec_t

    3,060
    834
    Jul 7, 2015
    0W would be ideal :D. I share Bob's misgivings. If you want a loud noise (= loud 'music') just use headphones. That way you damage your own ears and nobody else's.
     
    BobK likes this.
  4. BobK

    BobK

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    1,688
    Jan 5, 2010
    Yipes. Just did a Google image search. I had no idea that hauling around massive audio systems on a bicycle trailer was a "thing."


    Bob
     
  5. budget minded

    budget minded

    3
    0
    May 13, 2016
    golly you're quick to jump to conclusions!

    i don't plan on riding trails OR through residential sections with my system. i love nature BTW. i gave up a LIMB for my commitment to mother earth junior, and still fight the petroleum devil every way that i can, and this is the best way.

    i plan on using the system at biking events, tailgate parties and downtown on club nights. you'd be surprised by just how many people enjoy a street party, especially if it's a bicycle system, and from my own anecdotal experience, if you're playing FUN music no-one else will, especially sucker club DJs who wouldn't know funky or upbeat if they watched 100 b-boys tripping over it.

    i rode around downtown with some local cyclists and someone else who had a system a couple weeks ago and everywhere we went, people were loving it. it's the ONLY fun i've had in this hillbilly gangsta crap town.

    a good bike system is ammo against global warming causing cars and small penis compensating coal stacking TRUCKS with loud systems. i have moral objections to those, especially when they have drunken motor revving parking lot parties right outside my apartment with their gangsta crap & mexican hillbilly music.

    first off suggestion that ANYONE EVER ride with headphones is criminally negligent advice that could get someone killed.

    second, you can't dance with headphones... it just doesn't work, trust me, i've tried, and the whole point of building this system is to share all of the upbeat and funky dance music all the crap head soulless techno and gangsta crap clones as well as the local banda everywhere you go crowd (there ARE other types of lating music you know?) out there refuse to play.

    it's about fighting back against the forces of suckhole music and living like an effing PRISONER in apartments that i've had it up to here with that have kept me from dancing since 1990. dancing is how i socialize, especially when it comes to seeking the company of a woman. if you're not part of the solution, you're part of the problem.

    all of this technical advice on circuit design has REALLY helped a lot in designing this system. thanks so much!
     
    Last edited: May 14, 2016
  6. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Okay, now that you have explained your need, I am willing to help.

    If I understand correctly, your amps are run by 36V supplied by 3 12V batteries in series. If this is so, put one capacitor, rated for 12V across each of the 3 batteries.

    But, that does not sound right to me. Where are you getting audio equipment that runs off a 36V battery? I would think that they typically run off 12V (or more like 14V) since they are produced for use in cars.

    Bob
     
  7. budget minded

    budget minded

    3
    0
    May 13, 2016
    i was planning on using 2x100 & 1x400 watt volt hungry class D amps, but 7 amp hours, apparently, is nowhere near enough to power such a system, and i'm totally back to square 1 anyways as the schwinn trailer i planned on buying, with a 28 1/2" or more wheelbase suitable for mounting a pair of 14" wide car boxes is no longer at walmart, and i'm going to have to settle on an average trailer too narrow to even fit 10" boxes.

    now that i know of a shop where i can get time using real power tools, i'm thinking of going back to my "big dream" plan and custom fabricating a subs enclosure out of fiberglass and maybe even going with 8 woofers, as well as starting out with less power hungry 50wpc modules so i can get rolling with a couple of $20 12v 7.2ah batteries until i have a billion dollars to switch to li-poly and get bigger amps.

    i'm VERY upset that the trailer is gone! i planned the whole system around it, and MOST trailers are lucky if you can fit 22" of whatever between the wheels. i swear the whole world is conspiring to keep my from EVER dancing again.

    fiberglass seems to be the best way to squeeze at least 4 x 12" woofers onto a tiny bike trailer. it might even turn out to be cheaper than a couple car boxes and will definitely be lighter. i'm modeling ways to get an atypical rounded box in my head. i hate how most fiberglass boxes are stretched over rectangular boxes that create really pointy corners at the bottom, like this

    [​IMG]

    sure... see the same thing a billion times, but when you try to find an example to illustrate, suddenly no one's making 'em like this anymore... *sigh*

    i'm thinking of ways to not only round the corners, but the transition to the base too for a more bubble shaped enclosure, POSSIBLY even using the natural pattern of the fleece it's built on instead of doing the bondo & paint thing. there's a building demo on youtube where the builder starts out with a plaid pattern sheet of fleece that i thought looked really cool au naturel with epoxy as a sort of clear coat even if the surface was stippled.



    it might not be the coolest pattern ever, but i kind of like that effect. i was disappointed when it got bondoed and painted over.
     
    Last edited: May 17, 2016
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