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Questions about a singing arc

  1. May 20, 2012 #1
    Alright, so I'm building the singing arc that's in this schematic.


    Now my first problem is obtaining a 60 volt input. Will I get a usable 60 volts (consider current spikes) if I bridge rectify a 120 volt wall current, obtaining a -60 and +60 line out, and then just take the +60 output lead as my source?

    And my second question is, why does the schematic use different line notations (one line, and many lines) to show that an output goes to ground? Is there any reason for this?
  2. jcsd
  3. May 20, 2012 #2

    jim hardy

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    that's a bit on the dangerous side for it ties your circuit straight to the wall outlet.
    It might be okay until you plug it into one that's wired backward, ie H and N swapped.
    But when you rectify it you'll charge your filter cap up to the peak, 120√2 volts not 60.

    I strongly suggest transformer isolation.

    Look in hobby sites for something like this but with current you need

    now you're into the drafting standards of that particular shop.

    My intuition is that they made a circuit common track on the board(the single lines) and tied it to earth(the multiple line) at one point (probably a chassis mounting screw).

    Note your circuit's audio in jack.
    One arranges his common track so there's no voltage drop along that track between the audio jack low side and the reference pin of that modulator.
    Note he could have drawn that multiple line ground symbol at bottom of audio input jack, it is after all the same elecrtical node, but then it would look to the eye as if all ground currents to that 5 amp schottky and fast diode flowed through that part of track between audio input jack and that modulator .
    Any resulting voltage drop would look like input to modulator.

    SO he put the symbol over closer to those large loads, i'd say as a subtle hint to the guy laying out the board to make it that way.

    Yungman will back me up here , i hope - Once you are accustomed to such problems from board layout, that hint is about as subtle as a stomach pump.
    Grounding isn't magic.

    old jim
    Last edited by a moderator: May 24, 2012
  4. May 24, 2012 #3
    More questions about a singing arc


    I've successfully constructed a singing arc prototype, and now I'm building the final design in the schematic above. Previously, I had an issue with delivering 60V at 2A to my circuit, but I've solved this by rectifying the output from a 3A variac. Now my only questions are:

    1. I'm using a relatively low pulsed DC frequency that's coming directly from the wall. Therefore should I be worried about voltage spikes, or do you think my circuit can handle them?

    2. In the schematic at top, what do the lines through the 47k and 10k pots mean? Is there a lead going from pin 2 to the 47k pot, and is the 10k pot attached to the wire at its top? Or are the lines just there to show that the pots are variable?
    Last edited by a moderator: May 24, 2012
  5. May 25, 2012 #4

    Maybe it will be safer if you got to do this project with someone who can understand electronics and will be sitting next to you -- maybe even doing most of the work. I mean it, not in a menacing way, but in a considerate one.

  6. May 25, 2012 #5


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    i think it would by kinda interesting to see what happens.

    i have no idea what that IC does or what the circuit is supposed to do, but i think it might be interesting to see what happens when he/she plugs it into the wall.:eek:
  7. May 25, 2012 #6
    "Maybe it will be safer if you got to do this project with someone who can understand electronics and will be sitting next to you -- maybe even doing most of the work. I mean it, not in a menacing way, but in a considerate one."

    You know ... I understand electronics pretty well, and I just finished building the circuit. :(
    All that's left is to decide whether or not to connect those leads to the pots or not. Then it's go time.

    @rbj - It's an electric-arc speaker. Check this out:

    Now it's either going to work, or it's going to explode. :)
    So, does anyone have an idea about what the wiring notation means?
    Last edited by a moderator: Sep 25, 2014
  8. May 25, 2012 #7
    That's what I meant, seing that you can't be sure about the potentiometers. What you are referring to is the third pin, the cursor. For the 10k one, it's connected to the upper pin, for the 47k -- business, as usual.
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