Shaft Balencer Curcuit

Discussion in 'The Projects Forum' started by Colin Stone, Dec 26, 2006.

  1. Colin Stone

    Thread Starter New Member

    Dec 26, 2006
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    Hello to all
    New to this site, in fact, I was looking for a 6-0-6 Trans when I came across this page. Good thing I did because I've been looking for some answers to this fun project I been working on. I build turbine engines to run in model jets and I have built one that runs at 160K-175K rpm range so I need a better balence. My ? is what is the purpose for a power rectifier mr856 joining the drain and source leads of a 30A,50v,.040ohm N-channel Mosfet. The drain is connected to the cathode of the MR856 and that is also connected to the 6v side of a 6-0-6 transformer 1.2VA. I have to shrink the schmat to upload so bare with me awhile.
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Whenever we remove voltage from an inductive load (a relay, a motor), that load developes it's own very high short-lived voltage. This is called "inductive kick." The diode in your circuit shorts that voltage spike around the mosfet, thereby protecting the mosfet.
     
  3. wireaddict

    Senior Member

    Nov 1, 2006
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    Although not terribly relevant here, this diode [also known as a free-wheeling diode] is also connected reverse biased across inductive loads in many instances for the same reason. The advantage of placing the diode across the load instead of the driver is that the diode catches all the energy from the spike while placing it across the driver transistor allows the current from this spike to bypass the driver but possibly find its way through an unprotected device elsewhere, likely zapping it [the unprotected device, not the diode].
     
  4. Colin Stone

    Thread Starter New Member

    Dec 26, 2006
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    Thanks for the tips.

    I also have a trigger trans in this curcuit and I was given a schemat for it but I also have another that points it in another direction. The schemat that came with the trigger transformer has leads one and two wired together the trigger going to the flash tube trigger lead and lead three going to a 106scr. The schemat that Iam building too has what looks like lead one thur coil out on lead two thur a MR856 diode anode side, the trigger side of the coil attached to the tubes trigger lead and the third pin to ground or negitive side of the DC. This coil is a 4KV output and the trigger lead is marked with a red line thats all I know about it. How would you determine what leads to hook up. I was under the impression that like any transformer you would need a thur voltage to create the voltage ramp up. Does this make any sense?
     
  5. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    If you can post a schematic diagram of your circuit, it would be much easier to answer any question you have about the circuit.

    hgmjr
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    This sounds like a xenon flash tube that works to freeze the motion so you can look for vibrations. As hqmjr has requested, a schematic is necessary at this point.
     
  7. Colin Stone

    Thread Starter New Member

    Dec 26, 2006
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    Here is the schematic of the Balencer curcuit Iam building to. There are some spots on there that Iam not sure of its intended purpose. After looking at it I will post some more ?'s

    I have removed the small jpeg use the other in the thread.
     
  8. thingmaker3

    Retired Moderator

    May 16, 2005
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    Colin, the jpg is too small to make out schematic details. Do you have a more readable one that you can post
     
  9. Colin Stone

    Thread Starter New Member

    Dec 26, 2006
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    Sorry about that. I used the wrong file. Let's try this one.
     
  10. Colin Stone

    Thread Starter New Member

    Dec 26, 2006
    6
    0
    Thats sort of the intended idea it freezes the point where the imbalence is and the meter tells you how much the imbalence is so you can remove it with a grinder. I am still working on getting a better picture to upload but I do have one uploaded take a look and tell me what you think about this curcuit.
     
  11. beenthere

    Retired Moderator

    Apr 20, 2004
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    Hi,

    Can't make out device labels and so on. Another post would be helpful.
     
  12. thingmaker3

    Retired Moderator

    May 16, 2005
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    Sounds like a useful tool!! I'm looking foreward to seeing the more legible schematic.
     
  13. Colin Stone

    Thread Starter New Member

    Dec 26, 2006
    6
    0
    Hi all
    Thanks for your patience on this upload bit. Here is a new upload of that schematic hopefully this will work better. If this is still too hard to see I will have to email it. I scanned it at 300dpi from a 8.5x11 paper.
     
  14. beenthere

    Retired Moderator

    Apr 20, 2004
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    Hi,

    Still can't read numbers too well, but I can get the sense of how the circuit works. Without an exaxt analysis, the input is a piezo device that responds to the vibration. The amps following it amplify & filter the signal. The logic gates finally use it to gate Q1, which causes a brief current through the optoisolator.

    The phototriac in the optoisolator turns on the SCR, which pulls a brief current through the top winding of the trigger transformer. When that happens, the xenon tube is ionized and flashes in synch with the vibration.

    The arangement of NAND gates makes a high-frequency oscillator. The two hexfets are gated on alternately, driving current through the step-up transformer. That makes the high voltage for the xenon tube.

    A trigger transformer will show different resistances on the two sides. The winding that the inducing current runs through will show a lower resistance. The one that generates the high voltage trigger will have a risistance significantly larger than the other. The only lead arrangement that is significant is on the trigger side - I think. I seem to recall that you may have to swap trigger leads if the original hookup gives poor results.
     
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