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  • cap dump schematic questions

    I have a couple basic questions about the attached schematic for creating a cap dump (from p. 47 of the intermediate handbook).

    A switch is shown (I've circled it in red and labelled it) between the positive post of the run battery and two other circuit branches, one going to the top of the main coil, the other going to the 555 chip circuit. I’m assuming there’s no physical switch there, and that it’s just an area that functions like a switch. Can anyone confirm this for me? I want to make sure if there’s a part I need to buy, I get it.

    Incidentally, the reason I can conceive of it as a virtual switch is that when the battery is pulsing current it would “close” the return path from the main coil to the battery positive, and when the battery isn’t pulsing, it would “close” the return path for current coming from the 555 circuit. Is this correct?

    Another question is about the 7812 voltage regulator. I’m assuming the leg shown on the top, closest to the number 7812 is input, the one going out to the right is output and the other is ground (I've labelled them such to clarify my question). Is that correct?

    There’s a diode between the recovery coil winding and the capacitor and voltage regulator. It’s a single diode as opposed to a bridge rectifier which is in the older schematics. Would a 1N4007 work? If not, what diode should I put there?

    When the magnetic field in the inductor collapses, I’m assuming the back EMF goes out through the recovery coil along with the radiant spike (instead of going back into the run battery). Is that right?


    Schematic.jpg

  • #2
    here is a corrected version of the Sch
    Attached Files

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    • #3
      the new schematic and my original questions

      Thanks RS.

      So it seems the voltage regulator is now both turning on the transistor, and sending the current through it, instead of the current coming from the battery as before.

      It seems more certain that the leg of the voltage regulator going to the right is output, but can you confirm?

      Any comments on the switch I was asking about?

      Comment


      • #4
        Hi Cmor,

        The voltage regulator supplies a constant 12 volts to both the BD243C transistor and the H11D1 opto coupler thru the leg going to the right. And no, the regulator doesn't trigger the transistor. The opto coupler keeps the run battery completely isolated electrically from the capacitor, 7812 regulator, DB243C transistor, IFPR260 FETs, and the charge battery.

        The 555 timer circuit causes the 2n4401 and 2n4403 to trigger the H11D1 opto coupler which in turn triggers the transistor. The capacitor is discharged thru the FETs when the transistor turns them on. The timing of the 555 therefore determines when the cap dumps rather than comparing the voltage on the cap to a given value. A comparator circuit is actually a better way to do a cap dump.

        The switch you were asking about is simply and on/off master switch for the entire device.
        Last edited by Gary Hammond; 08-11-2018, 05:20 AM. Reason: add info

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        • #5
          Hi Gary,

          Thank you.
          I appreciate the clarification of what the voltage regulator is doing. I was clear on the function of the optoisolator, but confirmation is always welcome.
          I still remain a bit confused about the switch though. Do you mean, rotating the wheel is the "switch" or is there something physically there, in that part of the circuit, that I need to install?

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          • #6
            Another question

            Hello again Gary,

            I forgot to add another question to my last message. It's regarding the recovery coil. I think I get it, but I just want to confirm. In my case, I have 8 power windings. All I need to do is isolate out one of them right - and then hook the diode to the bottom end (would a 1N4007 work?) the cap to the top end, etc. as shown in the schematic?

            By-the-way, Aaron told me a comparator circuit is better, but that it's more advanced and may be a bit much at my stage, since I'm new at circuit building, so that's why I opted for this one. Since I'm living in Costa Rica and have already ordered everything from the states, I'm basically locked into this method for now.

            Comment


            • #7
              Originally posted by Cmor View Post
              Hello again Gary,

              I forgot to add another question to my last message. It's regarding the recovery coil. I think I get it, but I just want to confirm. In my case, I have 8 power windings. All I need to do is isolate out one of them right - and then hook the diode to the bottom end (would a 1N4007 work?) the cap to the top end, etc. as shown in the schematic?

              By-the-way, Aaron told me a comparator circuit is better, but that it's more advanced and may be a bit much at my stage, since I'm new at circuit building, so that's why I opted for this one. Since I'm living in Costa Rica and have already ordered everything from the states, I'm basically locked into this method for now.
              Hi,
              There is nothing Advance of anything unless you find it out on your own!.. the comparator is a device that auto triggers when the set Voltage is reached,that you can manually set with the pot in the circuit arrangement.
              Rgds,
              Faraday88.
              'Wisdom comes from living out of the knowledge.'

              Comment


              • #8
                Hi Cmor,

                I still remain a bit confused about the switch though. Do you mean, rotating the wheel is the "switch" or is there something physically there, in that part of the circuit, that I need to install?
                The switch is a manual toggle switch that you can turn off to stop the machine from running. It is only a convenience so you don't have to unhook the battery leads to stop it. It's optional.

                All I need to do is isolate out one of them right - and then hook the diode to the bottom end (would a 1N4007 work?) the cap to the top end, etc. as shown in the schematic?
                Yes. That is correct.

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                • #9
                  Thanks Faraday,

                  Finding out for oneself is definitely what counts, and comparisons made by others may be of limited value, I agree. Aaron just wanted to make sure I chose a design I could actually build, which I appreciate.

                  Your description of how the comparator works certainly sounds straight-forward, though building one is obviously different territory. Once I get the Mosfet version built and working though, thereI'll try to build a comparator.

                  Comment


                  • #10
                    Originally posted by Cmor View Post
                    Thanks RS.

                    So it seems the voltage regulator is now both turning on the transistor, and sending the current through it, instead of the current coming from the battery as before.

                    It seems more certain that the leg of the voltage regulator going to the right is output, but can you confirm?

                    Any comments on the switch I was asking about?
                    Hi Cmor,
                    The switch at the primary (drive battery) may be a simple toggle switch to turn on the Radiant Oscillator, or it may well be a split-commutator switch as per JB 1984 machine for the sake of back-popping of the drive battery. the idea is to isolate the drive battery from the oscillator circuit at the instant when the dump occurs and re-connect it when it is charging the capacitor.
                    Rgds,
                    Faraday88.
                    'Wisdom comes from living out of the knowledge.'

                    Comment


                    • #11
                      Faraday, that is NOT what that switch is for, PLZ dont confuse PPL........ it is just a on off power switch..........

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                      • #12
                        Thanks Gary & Faraday for the clarification about the switch. I feel a lot more at ease.

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                        • #13
                          Connecting the capacitors in series and parallel

                          I understand that John used 4 capacitors and that they were connected both in series and parallel.
                          I can understand one or the other, but don't know how to hook them up both ways.
                          Can someone explain this?

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                          • #14
                            Think of it like a battery bank....if you need 24 volts you put two in series....if they don't have enough current then you take another two that are in series and you take that 24 volts positive to the original 24 volts positive and negti e to negtive. Same as parallelling two 24 volts batteries but each 24 volts battery is actually two 12vs in series. Same with caps. Have a rated capacity of 50 volts but need 100 put two in series...need more capcitance then parallel them jas as batteries. Hope that helps

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                            • #15
                              Thanks Bradley. Using your battery example, would it be like this?

                              Screen Shot 2018-08-19 at 8.33.58 PM.jpg

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