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558 timer for triple timing use...

Discussion in 'General Electronics Chat' started by hackware, Jul 30, 2017.

  1. hackware

    hackware New Member

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    I'm just starting back designing with the 555 again, after a few years away from silicon valley...

    I need 3 (4?) timing functions, so a 558 seems like a good fit, if they can live with the reduced pins available to each timer.

    Functions needed:
    1) variable speed oscillator
    2) variable pulse width monostable (triggered by oscillator)
    3) variable voltage output (another monostable gating oscillator pulses to voltage accumulator circuit)
    4?) variable oscillator duty cycle.

    What I'm building is a fish zapper to get rid of some giant catfish in my father's pond. They are killing off all the other fish.
    (and YES, it is legal in Mississippi if done on your own property)

    Anyway, to get the signal to match the water (must be tuned because it's a pond, not running water), I need to vary frequency, pulse width,
    and amplitude.
    (borrowed a couple of the cheap fish zappers, but they could not be adjusted for my water conditions, and the commercial rigs cost many
    hundreds of dollars...)

    This signal will trigger a car battery/ignition coil circuit driven by a pair of 3055 transistors.

    I'm gonna build a test circuit with individual 555 chips, but want to use a single 556 or 558 chip if possible...

    Any assistance and/or ideas would be great... :)

    william...
     
  2. crutschow

    crutschow Well-Known Member Most Helpful Member

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    Sounds feasible, so what are your questions?

    You have 4?) variable oscillator duty cycle.
    Why the question mark?
    Is that a separate oscillator from that in 1)?
    If so, I see no need for a variable duty cycle unless you want to eliminate 2).

    If you describe the functions you need (exactly what the circuit does) rather than the circuits you think you need, we can better help you.
     
    Last edited: Jul 30, 2017
  3. davenn

    davenn Active Member

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    never seen or heard of a 558 .... nor has google, apparently
     
  4. dave

    Dave New Member

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  5. crutschow

    crutschow Well-Known Member Most Helpful Member

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    My Google has: ;)
    upload_2017-7-30_20-13-28.png
     
  6. Colin

    Colin Member

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    555's are 5 cents each.
     
  7. davenn

    davenn Active Member

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    WOW ... I googled NE and LM 558 ... zippo LOL
     
  8. Colin

    Colin Member

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    It's stupid to use any chip other than 555 as you have to think about the pin numbering.
     
  9. hackware

    hackware New Member

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    what i need is a bunch of dead giant catfish... ;-)

    signal wize, need a series of variable voltage, variable duration, variable frequency pulses...

    just downloaded kicad and started on a scat... be back in a couple of daze... :)

    william...
     
  10. alec_t

    alec_t Well-Known Member Most Helpful Member

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    If ultimately you're driving an ignition coil then won't just one oscillator do, providing you can vary its pulse frequency, width and amplitude? One '555 and 3 pots?
     
  11. hackware

    hackware New Member

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    Yes, you are correct. It's just beyond me to do so... I'm mostly a software hack, with a bit of hardware design experience when needed. Most of my past work was as a research team member with bunches of support staff, so I stuck with systems work where I knew what I was doing (mostly)...

    Most of my hardware work was with the old 8051 family of chips, and other data related I/O. Beyond sensors and actuators, I b a newbie...

    william...
     
  12. AnalogKid

    AnalogKid Well-Known Member

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    If 1) is driving 2), then that equals 4?).

    For 3), what is, and what is the intent of, a voltage accumulator circuit? Integrator, lowpass filter, something else?

    And, which of these various circuits is driving the power amplifier that drives the ignition coil?

    ak
     
  13. crutschow

    crutschow Well-Known Member Most Helpful Member

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    You can do variable frequency but I don't see how you do variable spark duration with an ignition coil. :confused:
    The spark duration is short, and is fixed by the coil design and output load.
    Changing the input pulse duration can vary the output spark voltage however.
     
  14. hackware

    hackware New Member

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    You just hit on why I started this thread...
    I started out with a vague memory of some work on controlling a laser exciter (20+ years ago) where we gated a variable frequency stream of pulses of variable voltage to a flyback/telsa generator...
    I forget exactly what ended up working, but it took them a year or so of fiddling with everything to get the thing to fire... (most bar code scanners today are based on final result...)(Dr Brown spent 5 years studying why grass is green instead of blue... :)

    Anywayz, all you fellas have much more practical experience in this area, and I'll research anything you point out for me...
    (I don't expect nor want everything done for me, just 2 squeeze between yer ears... :)

    My thoughts were to break down required functions into individual modules and tie them together.
    (even if on same chip like 558)
    Then opto-isolate to a pair of 3055 transistors to drive the coil.

    The final output will go to a pair of 10 guage wires ending in 12-24 inches of chain to drag on bottom of the pond.
    (already tried 3 times with various loaned fish zappers available on ebay and such to little effect (only brought up small fish))
    (need more OOMPH...)

    william...
     
  15. hackware

    hackware New Member

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    ummm, I've thought of it like that b4... ;-)

    but i've been called worse...

    lol...

    william...
     
  16. AnalogKid

    AnalogKid Well-Known Member

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    Don't worry about it. Colin routinely insults people who he thinks aren't as smart as he thinks he is.

    ak
     
  17. hackware

    hackware New Member

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    well, he could be rite...

    i ran outta fingers keeping track of 4 555 timers...

    thought less pins in a 558 would be ez'r ;-)

    william...
     
  18. shortbus=

    shortbus= Well-Known Member

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    Maybe, if I'm understanding you, having both wires on the bottom is the problem. Wouldn't it be more effective with one lead on the surface(the boat skin?) and the other on the bottom. To have the electricity in between the two outputs. Never did this before but makes more sense to me. Or you could get some dynamite.:) Have seen that done to clear a lake once.
     
  19. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    Spark duration if you need this to be adjustable then an ignition coil might not be the way to go, ignition coils are flyback devices, the turns ratio is usually only 100 : 1, so to drive a continuous spark you'd need a very high input voltage, an ignition coil discharges its energy in a similar way to a marconi oscillator and controlling spark duration might be tricky.
    You might be better off winding your own tranny, something like an Etd25 or something like that.
    How do you 'tune' a supply to the pond, does the mass of water have a particular resonant freq?
     
  20. hackware

    hackware New Member

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    Electrically you are correct. I did not state things well. Both wires are connected together to the high voltage output, and the "ground" is attached to the negative return path (the boat and battery negative). Dual wires are used to compensate for differences in conductivity of the water across level gradients along the pond bottom, and the different pond bottom materials (sludge). Mississippi Agriculture Department did a bottom analysis years ago, and stated there were great differences along our pond bottom (typical) because of various trees (and other factors), and that a clean out was advised...

    william...
     
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  21. hackware

    hackware New Member

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    You could be correct as far as the final stage transformer is concerned. I'm going with an automobile ignition coil (at least at first) because the newer ones (still pure flyback) put out 25-40 KV, are fairly robust, are sealed, and cheap (got 2 off ebay for $5 each).

    This high voltage stuff is new to me, as my only experience is with control circuits/software (mostly software)...
    (unless you go back to my navy radar dayz, 40 years ago, and i was a tech then, not an engineer...)

    If it ends up requiring me to wind a custom transformer, guess I will. But only if required...

    As far as the "tuning" goes, yes, you DO tune the signal to match the pond water. This is according to the Mississippi Agriculture Department, which has the more expensive equipment which can do so. Different ponds contain water from different sources (more or less iron, calcium, etc...) and also contain different types of fish, runoff (watershed, soil, manure, fertilizers), and contaminants (trees, dead animals, fish food), which can greatly change water resistance and/or "resonance". (the ag guys are farmers and don't really know much (like me) about their equipment, but they do know about how different ponds require different settings to work)(wish I could just get them out here)

    Most of the fish zappers available for sale out there, actually state they only work in flowing water, specifically NOT in ponds...
    (ponds retain heavy sediment which cause my problems...)

    Your insights are why I started this thread.

    Thank you very much...

    william...
     

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