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Common Ground Switch(Generator Mode) & Adding a Generator Coil - Observations

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  • #16
    Hi Gary,

    In the process of learning about the SG and its components I just watched some tutorials regarding diodes. Before that, I was under the illusion that as long as voltage/amperage rating where more or less the same you can interchange one diode with the other. But I learned that different diodes behave very different under certain circumstances, I have some questions regarding diodes which I hope you can help me with:

    A single 1N4007 will probably blow as the current will exceed it's one amp rating. I use two 1N5408 diodes twisted together in parallel, and they handle the current just fine.
    I assume that putting a couple of 1N4007 in parallel would do the trick as well? Or is the 1N5408 so similar in characteristics to the1N4007 that they can be interchanged?


    The D3 diode of the comparator circuit (12V zener, 1N5242) I could only find in packages of 250. So at the moment of ordering I looked for a diode with similar specs, available in smaller quantities and ordered this one:
    Nexperia BZX79-B12,113
    https://nl.rs-online.com/web/p/zener-diodes/0508163/
    spec sheet: https://docs.rs-online.com/13a2/0900766b80b4c56e.pdf
    I was wondering if you have any idea if I can replace the 1N5242 with the zener diode I bought without running into any trouble?


    Many thanks in advance,
    Rodolphe


    ​​ Diodes question.png
    Attached Files
    Last edited by pearldragon; 05-01-2020, 06:30 AM.

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    • #17
      Hi Rodolphe,

      I assume that putting a couple of 1N4007 in parallel would do the trick as well? Or is the 1N5408 so similar in characteristics to the1N4007 that they can be interchanged?
      The 1n5408 and 1n4008 are both common diodes rated at 1000 volts PIV (peak inverse volts), however the maximum foward current rating of the 1n4007 is only 1 amp as opposed to the 6 amp current rating of the 1n5408. Switching speeds and foward voltage drop are about the same for both. So two 1n4007 in parallel could safely handle up to 2 amps and two 1n5408 in parallel can safely handle up to 12 amps. I had both on hand and went for a little over kill.

      An ultra-fast switching diode here would be desirable. Two UF4007 diodes in parallel would be able to handle up to 2 amps, and a MUR3020WT would be able to handle up to 30 amps.

      The Nexperia BZX79-B12,113 zener should work just fine. This is only used as a voltage reference and is rated the same as the 1n5242 in both wattage (500 mw) and zener current (20ma max, 10ma typical).

      Gary Hammond,

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      • #18
        Hi Gary,

        UF Diodes
        An ultra-fast switching diode here would be desirable. Two UF4007 diodes in parallel would be able to handle up to 2 amps, and a MUR3020WT would be able to handle up to 30 amps.
        Could you maybe explain me in a bit more detail how using one of these UF diodes would yield better results? Is there a specific reason why you did not use them yourself? Or did you wanted to stick to the handbooks first before interchanging parts?


        Power rating (variable) resistance
        I’m planning to do some of my own measurements on the efficiency of single/double pulsing area/rpms. To do that I want to build in some form of the “trigger switch”, as mentioned on page16/17 of the Advanced Handbook. But reading those pages and comparing them with the Intermediate Handbook page 9, got me confused a bit for the following reasons:
        -In the Intermediate Handbook page 9 a potmeter is mentioned of 1W.
        -In the Advanced Handbook page 16 a potmeter is mentioned of 25W, replacing the 12-Ohm 10W resistor(s).

        Since up to this point I’m still working with my potmeter* from the Intermediate Handbook without any problems, I assume the 12-Ohms resistors didn’t need to be 10W, and neither is there a reason for using a 25W potmeter if a 1W is sufficient? If correct, I assume that the 10W resistors / 25W potmeter are just what they had lying around when doing the Advanced Manual tests.

        I’m asking this since I was in doubt whether I will make a switch to completely bypass my potmeter, or use a low resistance fixed resistor (so I can toggle between this fixed resistor and the potmeter) and started to doubt the wattage of this fixed resistor because of the above mentioned.


        *my potmeter currently is a 200 Ohm, 2W, 3%, 10 turns.

        Many Thanks in advance,
        Best regards,
        Rodolphe

        Comment


        • #19
          Hi Rodolphe,

          Could you maybe explain me in a bit more detail how using one of these UF diodes would yield better results? Is there a specific reason why you did not use them yourself? Or did you wanted to stick to the handbooks first before interchanging parts?
          This was a generalization and may not really matter at this particular location in the circuit. You can also eliminate the diode altogether for fastest charging if the secondary is only 6/10 volt less than the primary at the start. The two batteries are essentially in parallel with each other and will equalize voltage between the two through the power coil ....... minus the forward voltage drop across the charging diodes. If the extra diode is added, the combined forward voltage drop is 1.2 volts and allows for charging a secondary battery that is 1.2 volts lower than the primary without voltage equalization taking place. But equalization isn't all bad, because it results in faster charging of the secondary. And once the secondary battery voltage exceeds that of the primary the current draw falls off any way.

          Peter Lindemann has pointed out that the ultra fast diodes attached to the collector/power coil junction deliver a higher voltage and faster charging to the secondary battery than the slower speed diodes. The slower speed diodes (1N4007), however, kick back more energy to the primary battery resulting in less current draw and a longer run time. So it is sort of a trade off and up to you which way you want to go. Faster charging of the secondary vs longer run time from the primary battery.

          Peter also demonstrated what an ultra fast diode added to the battery swapping circuit in his "Beyond The Advanced Handbook" presentation does. It caused the radiant energy to manifest at all points in the circuit causing the neons across the transistors to light up brightly! The volt meters across the batteries were glitching and sometimes going off scale! Of course this was operating at 24 volts and not the usual 12 volts everyone starts out with.

          I did use a MUR3020WT ultra fast diode in the attraction motor I made, and it charges the secondary very fast. I also used a UF4007 in the SSG driving the two-stage mechanical oscillator my grandson and I built. It also charges pretty fast. But I didn't want to go back and change out all the diodes in the other SSGs that I already had built previously.

          Since up to this point I’m still working with my potmeter* from the Intermediate Handbook without any problems, I assume the 12-Ohms resistors didn’t need to be 10W, and neither is there a reason for using a 25W potmeter if a 1W is sufficient?
          I use a 100 ohm, 25 watt, single turn potmeter in all my builds now. I've burned out a few low wattage pots, so I tend to go for a little overkill with them.

          Gary Hammond,

          Comment


          • #20
            Hi Gary,

            Thanks for your explanation regarding the workings of the different diodes. I haven't looked at the "Beyond The Advanced Handbook" yet, but i did bought it already.

            I use a 100 ohm, 25 watt, single turn potmeter in all my builds now. I've burned out a few low wattage pots, so I tend to go for a little overkill with them.
            Ok, thanks. I guess since my 2W potmeter hasn't burned out yet, any fixed resister with at least a 2W rating should be good (and if not, I'll find out pretty quick too ).

            Thanks!
            Regards,
            Rodolphe

            Comment


            • #21
              Hi Gary, RS,

              I was a bit in doubt in which thread to post the following questions, but it think is not a bad choice.

              I actually wanted to wait with learning/experimenting about the generator coil till I have my SG in the ballpark of your SG, performance wise, but since I’m still waiting for parts, decided to make the preparations for some testing with the generator coil, which I attached to my SG.

              Apart from the tests as described on page 41 of the Advances Handbook, and the slightly modified version in your post 11, I would like to do the experiments that Aaron shows in his video: https://www.youtube.com/watch?v=s6iYRjcBu-Q

              1- If I understand correctly, his circuit looks like figure 1, as in the attachment. Now he mentions that it is not recommended to switch/short-circuit the generator coil directly with a Reed Switch. Is this because the amperage in the short-circuit can exceed the Reed-Switch rating? I also saw that there are Reed Relays available too with a higher amp rating, but switching time becomes critical with my 21 magnet rotor it seems. How about a Hall sensor?

              2a- Assuming I would need indirect switching for the Reed switch (/hall sensor) to live longer, would the schematic as per Figure 2 work?
              2b- Would an SCR (instead of a MOSFET) or another switching device be better suited here?


              3-Would I be able to achieve even more output from the generator coil (=charging the capacitor to higher voltage) if I would use an individual trigger coil
              to operate the MOSFET, see Figure 3


              Thanks,
              Rodolphe

              2020-12-22 Attachment.pdf

              Comment


              • #22
                Hi Rodolphe,

                1-
                Is this because the amperage in the short-circuit can exceed the Reed-Switch rating?
                I would assume that is correct.
                How about a Hall sensor?
                I have seen circuits where people have used hall switches to trigger either a FET or an SCR.

                2a-
                Assuming I would need indirect switching for the Reed switch (/hall sensor) to live longer, would the schematic as per Figure 2 work?
                What you show looks reasonable, but I would have to build and test it to know for sure.

                2b-
                Would an SCR (instead of a MOSFET) or another switching device be better suited here?
                An SCR latches on until the polarity either falls to zero or reverses. Without trying it, I don't know whether it would work without some extra circuit components.

                3-
                Would I be able to achieve even more output from the generator coil (=charging the capacitor to higher voltage) if I would use an individual trigger coil
                to operate the MOSFET, see Figure 3
                Don't know the answer to this. You would have to try both ways and then compare results.

                I've not experimented with generator coil shorting circuits myself, so am not a good source for information on the subject. I do know that this is the principle used in magnetos which I do have some experience with on small engines. The point and condenser system can be troublesome, so I frequently eliminated them in favor of a solid state switching module which was very reliable. Could one of these ignition modules be used with the generator coils? I don't know as I haven't tried it myself.

                Gary Hammond,

                Comment


                • #23
                  Hi Gary Thanks For your answers!

                  Today I've ordered some reed switched and some Hall effect sensors too. The rest of the stuff I already had at home. Will do a series of experiments, and update here once done. But it will take me a while.

                  Regards
                  Rodolphe

                  Comment


                  • #24
                    Hi Gary, RS,

                    I've done a first set of tests, for the report/my findings please see attached file.

                    The point and condenser system can be troublesome, so I frequently eliminated them in favor of a solid state switching module which was very reliable.
                    not sure if I understand you correctly here: with a "point and consenser" system you mean a Reed Switch?

                    Bets regards,
                    Rodolphe
                    2021-01-06 - Generator coil Tests V1.1.pdf

                    UPDATE 2021-01-22
                    -Added an addendum for the HALL sensor circuit

                    Attachment UPDATE 2021-01-22.pdf
                    Attached Files
                    Last edited by pearldragon; 01-22-2021, 03:55 AM. Reason: Added an updated Hall sensor circuit

                    Comment


                    • #25
                      Hi Rodolphe,

                      not sure if I understand you correctly here: with a "point and condenser" system you mean a Reed Switch?
                      No, I didn't mean a reed switch. I was referring to the ignition system of a small, single cylinder, gasoline engine as used in lawn mowers and chain saws, etc.

                      Older designs use breaker points to short out the primary coil winding until the flywheel magnet is directly over the coil. At that moment in rotation, the points open to stop current flow and produce moderately high voltage from the coil current (induced magnetic field) collapse. The capacitor, in parallel with the breaker points, reduces arcing across the points. The moderately high voltage then induces a much higher voltage in the secondary winding of the coil, which is able to fire a spark plug under high pressure in the cylinder.

                      The breaker points and condenser can be replaced by a simple solid state ignition module which is much more reliable. These ignition modules were available in kit form to retrofit most any small engine. I installed and/or sold several of these years ago. Nearly all small engines now have this module embedded in the coil as standard equipment.

                      Gary Hammond,


                      Comment


                      • #26
                        Hi Gary, RS,

                        I've done a second set of tests, with loads and an corrected MOSFET circuit for the Hall sensor. For the report/my findings please see attached file.

                        Best regards,
                        Rodolphe
                        2021-01-23 - Generator coil Tests w. 10k Load V1.0 - ESF.pdf

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