Bedini RPX Sideband Generator



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Thread: Tuning Assistance

  1. #1

    Exclamation Tuning Assistance

    This problem of mine specifically refers to tuning the SG so to gain the sweet tune conditions

    I will place a video with fotos on soon however for now the problem is that I cannot achieve a sweet tune or point where the current suddendly decreases for a sudden increase in wheelspin. I have tried it all throughout the 1kOhm 3W Potentiometer to no avail. My magnet to coil core distance is about 3-4mm which is what was recommended. My wheelspin time is about 8-10 minutes though I do think the wheel I have is of a average standard

    So I have followed the instructions, the principle in setup WORKS(light flickers if output battery off) but just having problems trying to tune it

    Some imminent thoughts? Because this problem has not changed even with increasing the wheelspin time and is quite frustrating given the process in principle functions...

  2. #2
    Hi there.

    You are looking for the "sweet spot" but I am guessing you have built your machine in attraction mode which does not really have one. The other way to run the machine is repulsion mode which pushes the wheel away instead of pulling it in to the coil. Repulsion mode had sweet spots because of the physical load of pushing the wheel. Most people use attraction mode these days because it runs much cooler and is generally easier to tune.

  3. #3
    How do you come to the conclusion I have it in attraction mode? Because I have followed the Monopole Instructions and also applied the more recent instructions from the book.

    And if you are right how would I get into repulsion mode? What circuitry adjustment is required?

  4. #4
    Or are you talking about running a coil counter to how I currently have it to reverse the effect?

  5. #5
    As I said most people now a days have their rigs in attraction, that is what has been tought for years now. If you have the book then I believe it is all explained in there anyway. If you want to try repulsion mode then you could reverse all of your coil leads or flip your coils over. The coil is an electromagnet after all which is going to either attract or repulse the ceramic magnets depending on polarity.

    Caution if you play with repulsion mode however. It WILL cause heat on your transistors and you run a much higher chance of blowing them out. There are advantages to both ways but you are best off using attraction to start out with.

    Another thing worth noting is that there are smaller "sweet spots" in attraction mode but it's not quite the same. From your first post I got the impression you had probably read some old info where people were talking about the sweet spots. Even in attraction mode if you pay attention to your spikes per magnet pass you will find to a lesser degree some sweet spots where you will hit optimal rpm for lowest input. Just as it switches from say 3 spikes to two or from two to one you will have highest rpm for that draw. If you go a little past there you will consume a bit more current and eventually lower the rpm. It's something you get a feel for after tinkering with it for awhile.
    Last edited by BobZilla; 06-01-2015 at 05:55 PM.

  6. #6
    I did a simple test on my Coil and it turns out it is in Attraction mode. This simple test involves placing a small magnet facing North or South on the Core of the Coil then connecting the coil wires to a battery which either does nothing if the coil end is different to the magnet or forces the magnet away if different. From this one can determine if Attractive or Repulsive.

    Now NOT having an Oscilloscope how would I be able to find accurately the tune spots on a Attraction mode machine?

  7. #7
    Get yourself an LED and connect a 300 Ohm resistor to one leg of it. Add some leads, gator clips work good for this. Connect one side to your primary positive and the other side to the junction where the power wind connects to the board which is at the output diode but not the rectified side of it. The output diode which is connected to the collector right where the coil end connects.

    Put a white mark in the center of one of your magnets that you can point the LED at and this will be a simple timing light. Mount the LED on your coil in line with the center core. You will be watching when the coil is firing in relation to the core of your coil. When connected one way it will show you the ON period and if you switch the leads around it will show you the OFF period or the spike side so to say. As you adjust you will see more and less firings of the coil and the position where the mark shows up will change. Play around with that a bit and see what you can observe.

    The resistor value is not critical, you just need somewhere around 300. This is only there to protect the LED so as long as your getting it to light up and not burning it out your fine.
    Last edited by BobZilla; 06-16-2015 at 06:19 AM.

  8. #8
    Join Date
    Jul 2012
    Adelaide, South Australia

    It's easy & inexpensive to find the Sweet Spot in either mode using the same method. This method was detailed by John Bedini's instruction set on the Yahoo Groups. You can do it with a multimeter & a laser rpm meter that I got from the old Farnell website for A$29.95 - I'll bet you can get a hold of a good laser one for much less. The old forum test reports used this method almost exclusively. It takes much longer, but saves you rushing out to buy the latest 'scope. What you want is the fastest wheel speed for the lowest primary current draw. Multiply your rpm reading by the number of magnets on Your wheel & divide this by the current reading. Allow about 5 minutes settling time for each potentiometer setting. Then you can post what you get here & compare with everyone else on an even footing. Then, once you've calculated the final "magnets per minute per milliamp" values, it's easy to see which is the highest, so sub in fixed values until you duplicate this "m/m/mA" value.

    All The Best.

  9. #9
    Hi Barrie,
    I do remember people measuring up this way and have not heard anyone mention it in a long time. I prefer a light so I can see the pulses but it's good to have options when analyzing these things.

    Thanks for your input.

  10. #10
    Join Date
    Jul 2012
    Adelaide, South Australia
    I tried the pulsating LED once & between that & the spinning wheel, I think I must have been driven unto madness! So the rpm meter saved me from becoming a total nutter (or from becoming more of a nutter than I am today)! It takes me maybe a day flat out to finish running calculations to get the sweet spot, as once I get a good value with one resistance I home in on an ultimate sweet spot even to the point of going ohm-by-ohm. When I get organized & can retrieve my data successfully from my old computer & failed USB sticks (so much for data back-up!), I'll post on here the results for all my SSG's. When I get building again, I'll re-build the lot even better this time.


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