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Help finding components

Discussion in 'Electronic Design' started by thorin92, Feb 13, 2006.

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  1. thorin92

    thorin92 Guest

    Hello, can anyone help me with a project i am working on its an automatic
    firework launcher I got 15 fireworks and they all need to launch 1 second
    apart.

    I need ten 20 Farad capacator does anyone know where these are?

    thank you
    Hajim
     
  2. Macgyver

    Macgyver Guest

    There are a number of companies that make these, such as Panasonic
    (Japan), MaxFarad (Korea), ELNA, Nichicon and NuinTCK (Korea). They
    are commonly called Double layer electrolytic capacitors, Super
    Capacitors or Ultracapacitors (depending on type and brand).
    I dont know what country you are in so I cannot suggest which local
    distributors might supply thes brands. Most have a working voltage of
    2.3 or 2.5V.
     
  3. Jon

    Jon Guest

    You don't mention the voltage rating or the peak current that you need
    to supply. I think what you need is a double layer or "supercap".
    They are available in a 22F, 2.5V rating. See the Digikey catalog, for
    example. If you need higher voltage, you may have to use a
    series-parallel combination to get the capacitance/voltage combination
    that you need. You also may have to connect some equalizing resistors
    in parallel with each series cap.
    Regards,
    Jon
     
  4. thorin92

    thorin92 Guest

    thanks for your help

    Looking at how expensive they are, a series configuration is not an option.

    I need a lot of charge and a peak voltage of 200 VDC at the output of the
    circuit. I think can i use a voltage multiplier (diode cascade) ladder, with
    the capacitor discharge through it. Will this work?

    Thanks
     
  5. Look at the igniters' specs. What's the minimum current you need to
    put through them to make sure they fire reliably, and for how long?
    What's their resistance like; what's the minimum voltage you need to
    sustain across them during the above period?

    There's a reason most folks ignite rockets with batteries rather than
    capacitors, whether ordinary, super, or ultra.


    Mark L. Fergerson
     
  6. Rich Grise

    Rich Grise Guest

    What? What are the capacitors for? People have been doing this for decades,
    with no need for such an exotic part.

    Besides which, for firework ignitors, I wouldn't trust any purely
    electronic solution, especally at what sounds like your level of expertise.
    I'd go for something like a gearmotor driving a switch array with a cam,
    or driving some kind of rotary switch itself.

    Well, OK, there _are_ ways of doing it electronically that could be made
    reliable, but how much time do you have to spend learning how to do it?

    Good Luck!
    Rich
     
  7. Rich Grise

    Rich Grise Guest

    What the hell do you need 200V for? You can fire squibs with a 6V lantern
    battery!

    Go lurk for awhile - something will show up.

    Good Luck!
    Rich
     
  8. Pooh Bear

    Pooh Bear Guest

    Do you mean for their stored charge ?

    The large 'super caps' that are available aren't made for rapid discharge.
    Maybe you should reconsider your approach.

    Graham
     
  9. Mike Swisher

    Mike Swisher Guest

    A person using a nail board and a watch with a second hand (or counting
    intervals "one thousand-one, one thousand-two, one thousand-three...") should be
    able to ignite 15 pieces of fireworks at one-second intervals!
     
  10. Fireball

    Fireball Guest


    Works great for me for small finales you want to shoot electrical and not to
    bring all the equipment.

    pyrohobie
     
  11. Guest

    While capacitive disccharge firing boxes are today widely used in both
    commercial blasting and fireworks, the construction and safe use of one
    is far beyond the capabilities of someone believing that they need "ten
    20 Farad capacitors" to perform the task!

    To echo Mike's post, what this poster needs is a "nail board",
    sopmething simple to construct and easy to understand.

    Over the years, I've constructed roughly 15 simple BC
    (battery/capacitor) firing systems (none of which involved electronics)
    using capacitors ranging from 20 to 50 MFD charged by battery to
    voltages between 67.5 through 180 volts. All functioned as intended.

    Just for the record, I've never seen even a 1 Farad capacitor rated at
    over a few volts, which suggest to me a lack of electrical know-how on
    the part of the original poster.

    I would suggest that the most basic method for discharging 15 fireworks
    spaced one second apart would be to connect them together with 1-second
    of fast Visco, pleated quickmatch, or 1-second timing fuse between
    them. Beyond that, a nail board is likely a simple solution.

    Harry C.
     
  12. Macgyver

    Macgyver Guest

    Here is a simple model rocket launch sequencer using 555 chips and a
    single trigger to launch standard igniter based rockets at preset
    intervals. Scaleable to as many rockets as you need.

    http://www.designnews.com/article/CA6303111.html?nid=2321&rid=1132842908

    Just power of a 12V car (or similar) battery. No 20F caps at 200VDC?
    required (and A LOT simpler).
     
  13. maxfoo

    maxfoo Guest

    If you take apart one of those 'fluorescent low energy mini lightbulbs'
    you'll find 15-20uFd 200V electrolytic caps among other components.
    you can get these bulbs cheap now under $3.00 and there's 20bucks worth of
    parts.
     
  14. Yabbut, he'd need at least ten million of them to get his required
    capacitance.


    Best regards,
    Spehro Pefhany
     
  15. enducer

    enducer Guest

    Just for the record, I've never seen even a 1 Farad capacitor rated at
    Capacitors definitly come around these ratings! Most car audiophiles
    use these on their 12vdc systems , most in the 1-2 farad range! But no
    to get a little spark you definitly wouldn't need something this large!

    As well 'Power factor correction systems' (Research it on the web to
    long to explain) uses high voltage capacitors at very high ratings as
    well !

    Rob
     
  16. Alan Yates

    Alan Yates Guest

    Most modern ultra or super capacitors are still internally low voltage
    cells in series if they offer voltages over 3 V or so. They are
    generally "fast" electrochemical, no longer true electrostatic devices,
    utilizing extremely high surface area carbon materials and exotic metal
    oxide coated electrodes.
     
  17. Guest

    Precisely. They are not capacitors in the conventional sense of the
    term, more closely approximating a storage battery.

    Turning to firing system basics, the amount of energy stored in a
    capacitor is given:

    Q = 1/2 CV^2 Where:

    Q = Stored energy in Joules
    C = Capacitance in Farads
    V = Charged potential in Volts

    Since the stored energy is proportional to the square of the voltage
    but only directly with capacitance, the design of capacitive discharge
    firing sytems are generally optimized when relatively small capacitors
    charged to high voltages are employed.

    An added benefit of this approach is that it minimizes the effects of
    firing cable resistance through the use of high firing voltages, in
    turn allowing longer runs of smaller gauge cable.

    This is why so many pyros have converted the flash circuity in
    disposable cameras to serve this function.

    Harry C.
     
  18. Guest

    One step above the disosable camera system is Honeywell photo flash
    units. Many have a 2 second recharge so with a little visco, you can
    have 1 second ignition. 1000 V spike very quickly tapers to 380 V. Yes
    you can fry your self.
    In one setup, I attached brass wipers with detents to the underside of
    the flash unit. These wipers contact pairs of rivets on peg board
    framed with 2x2 stock. 42 cues with ten igniters possible per cue. If
    you don't share grounds, this system can not back feed so you do not
    need diodes. Just add a fire button, and wipers. On/off switch, charge
    indicator are already built in!
    There is a quick recharge self defence stun zapper that looks
    promissing for long chains.
    While not very sexy, this system works every time and cost squat. I
    bought a like new thyristor model still in the box for $10.
     
  19. maxfoo

    maxfoo Guest

    hmmm...... a 20 farad cap would be the size of a tall building, He most likely
    meant 20ufd.
     
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