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Should a Cap Dump Affect Rotation of Energizer?

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  • Should a Cap Dump Affect Rotation of Energizer?

    I built my second Bedini/Ihmotep Fan using more powerful fan and have setup an SCR, 16V Zener Diode and 450V, 270uF(M) cap using the schematic from here

    Once I got it running I noticed that every time the cap dumps (roughly 4 times a second) it seems to slow down the Fan a little and emits a type of soft knocking sound. I have tried some different Zener Diodes and CAPS and all of them do the same thing (albeit at different intervals). Is this the excepted behaviour?

    Without this CAP setup, it spins without this "knock".

  • #2
    Yes, this is normal. The circuit will adjust itself to the load, so as the cap charges up and the impedance changes (in the load) the rotor will speed up.

    It's the same reason why when charging a battery with the Bedini SG, the rotor will speed up as the battery voltage raises. You seeing the same effect, but in a shorter time frame.

    John K.


    • #3
      Thanks John, as part of further experimenting I tried a bigger 80V 8000uF CAP. This "seems" to have a better effect on the charge battery and starts at about 10V, charges to about 26V then dumps (although its hard to tell exactly with a voltmeter). However it's pretty slow and takes about 8 secs between dumps. Is there a maximum time between dumps that should be allowed? Would using a lower uF improve things?

      When using the 450V, 270uF it was hard to see exactly how high/low the cap charged and discharged as I don't thing the voltmeter could keep up. It seemed like it started anywhere between 16-19V and reached maybe 22-24V.


      • #4
        8 seconds is probably a bit too long to keep the ions in the battery moving in a charging mode.

        I generally go for a 1000uF 50v cap and place 2 1N4001 diodes in series where you have the zener. This will dump the cap at about 3v over the battery a few times per second. Charging is usually pretty good for the current draw, depending on the wire gauge of the coils in the fan.

        If you get the balance right, you can swap batteries for days or over a week before having to recharge them. Plus all of the free air

        John K.


        • #5
          I'm totally stumped now. I had this working ok and now the capacitor simply will not dump and hovers around the same voltage as the battery, if I manually remove the positive or negative from the charge battery it builds and I when I connect it again it dumps back down to about the level of the charge battery.

          I have been scratching my head for hours trying to resolve this, trying all sorts of things, different caps, zeners, shorting the cap, charging up the batteries, discharging them. From my reading I believe this is something to do with the SCR locking? I have 2 SCR's and tested them and they appear ok.


          • #6
            It has all the symptoms of your SCR latching. I would get a new one.

            John K.


            • #7
              Thanks once again John! I popped in to Jaycar and grabbed a few more SCR's, Zeners and 35V 1000uF ESR cap (had no 50V) and it's back pulsing away now about every second! I am going to test the old SCR's as I have this horrible feeling I may have connected the negative on the cap to the anode on the SCR previously. I'm kinda hoping they don't work or it may mean I have lost many hours of my life from my own newbie stupidity :P

              Lastly, would you mind elaborating about the 2 1N4001 diodes. Would they be in between the cathode on the zener and anode on the SCR? Also would 1N4004's work as I only have those at the moment.

              Edit: For the benefit of others reading this thread, it turns out I had also killed the zeners, so for anyone experiencing similiar issues, check the SCR AND THE Zener. I think I have vindicated myself and didn't wire anything wrong during my troubleshooting.
              Last edited by jelloir; 03-06-2014, 08:15 AM. Reason: Added note about checking Zeners


              • #8
                Hi jelloir,

                The 2 diodes go between the anode and gate of the SCR. The idea is to create a potential difference between the capacitor and the battery by using the forward voltage drop of the diodes. The diode's anode goes to the SCR anode and the diode's cathode goes to the SCR's gate.

                1N4004 diodes should be fine.

                John K.


                • #9
                  Great, I mistakenly (originally) thought the zener was in series with the diodes, did I mention I'm a newb . Anyway I have it working now using 2x 1N4934 100V 1A diodes, BT151 500R SCR, and 34V, 1000uF cap. It's pulsing so fast that I can't really tell how many times per second, but it's fast and can make out the tell tale "knocking". My volt meter on the cap thinks it's a steady voltage of about 13.12V, presumably due to the voltmeters sample rate with the charge battery currently at 11.97V.

                  I have noticed that the charge battery seems to plateau after a while, which looking at the state of charge I think is normal, but it just seems like a long time between getting to the next volt after an inititial jump when starting. I am starting to log my charging runs so I can understand this better.

                  I bought an assortment of CAPS, Zeners, Diodes etc to experiment with so should be good now.

                  Thanks again for taking the time to help.
                  Last edited by jelloir; 03-08-2014, 01:20 AM.