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Dummy Load II

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by jocanon, Jan 12, 2013.

  1. ronv

    ronv Well-Known Member Most Helpful Member

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    One last tweek. I'm trying to keep this one from oscillating. I think I'm done now.:D:rolleyes:
     

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  2. jocanon

    jocanon Member

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    ()blivion, so on the other hand I think I would want as much separation between the MOSFETs on the copper pipe for cooling purposes so is it just a trade-off between these two things and if so which one wins out, what is more important? Or I wonder if there is some way of shielding the wire from interference?
     
    Last edited: Jun 26, 2013
  3. jocanon

    jocanon Member

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    Thanks Ron!
     
  4. dave

    Dave New Member

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  5. ronv

    ronv Well-Known Member Most Helpful Member

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    Here is one thought. If you make the square say 6 inches on a side you could put a board inside of it. Since there are 4 op amps per package - one on each side. Put the 75 ohm close to the FET. The rest of the stuff could go in the middle. Just my 2 cents - and worth every penny.:)

    Ohh. Use the STP80NF12 like last time. It has a DC spec the one I used in the sim doesn't have.
     
    Last edited: Jun 26, 2013
  6. jocanon

    jocanon Member

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    I think that will work.
     
  7. jocanon

    jocanon Member

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  8. jocanon

    jocanon Member

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    nevermind
     
  9. jocanon

    jocanon Member

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    Hey Ron, in the latest updated schematic above in post 381, is R15 really still just the ammeter, or did you add another resistor there?
     
  10. ronv

    ronv Well-Known Member Most Helpful Member

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    Sorry, No it is just the ammeter.
     
  11. jocanon

    jocanon Member

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    Ok, that's what I thought. Thanks, I am working on building my order at Mouser. Did you get a chance to look at that box I put a link to in post 386, do you think it will be big enough?
     
  12. ronv

    ronv Well-Known Member Most Helpful Member

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    It may be hard to bend 1/2 inch pipe to fit nice in there. It will need a pretty large radius for the bends I think. If you don't mind the big one it would be better for the heat.
     
  13. jocanon

    jocanon Member

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    That makes sense...I'll stick with what I have then.
     
  14. jocanon

    jocanon Member

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    Will it change anything if I use the below instead of the ammeter from Hobbyking? I already have one of the below laying around and I am disappointed with the Hobbyking ammeter because it has two modes and I have to push a button to get it in mode 2 to be able to use it on the DL...call me lazy.

    http://www.ebay.com/itm/DC-100A-Amm...569?pt=LH_DefaultDomain_0&hash=item2ec8dacea9

    It looks like I will also need to get this because the ammeter with shunt needs an isolated supply:

    http://www.mouser.com/Search/Produc...SACvirtualkey58010000virtualkey580-NMV1212SAC
     
  15. ronv

    ronv Well-Known Member Most Helpful Member

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    Looks like it should work.
     
  16. jocanon

    jocanon Member

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    alright, I am going to pull the trigger on the parts order tonight.
     
  17. jocanon

    jocanon Member

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    Hey Ron, I found the ASC file in an earlier post, but it was not the updated schematic. Can you post the most recent version of the schematic in *.asc format from LTspice? Thanks!

    update:
    got it via email, thank you Ron!
     
    Last edited: Jul 6, 2013
  18. ronv

    ronv Well-Known Member Most Helpful Member

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  19. jocanon

    jocanon Member

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    Thanks Ron
     
  20. ()blivion

    ()blivion Active Member

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    Hi.

    For the MOSFET's and how close they can be on the pipe, I really don't think you will see much of a heat difference with them close together or far apart. The pipe being copper, should share heat from one end to the other at a really fast rate, and the whole thing should transfer heat to the water at light speed. So don't worry too much about the most efficient spaces between them. As for noise, as long as you keep all the gate wires short and don't twist them all together with other wires, you shouldn't be able to get them close enough to see any noise issues either. The issue with wire proximity is really about touching wires, or possibly long runs of two or more wires that are consistently somewhat close to each other.

    Edit: Don't be afraid to get multi-dimensional with your wire layouts if you can. Having say, all the gate wires pulled up, then all the drains pushed down, can give you just as much separation as if you did it left to right or forward and backward. But may or may not be easier to do.
     
    Last edited: Jul 9, 2013
  21. jocanon

    jocanon Member

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    Thanks ()blivion. I think I am going to try to get plugs for the MOSFETS/Current adjusting POT/+12v PAmmerter...basically anything that will reside off the PCB so that I can easily take it a part for possible future repairs. If I get a socket and put the signal wires to the gates next to the power wires going to the MOSFETS, will this create a problem?
     

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