Inductance

Discussion in 'General Electronics Chat' started by Chillum, Dec 8, 2014.

  1. Chillum

    Thread Starter Active Member

    Nov 13, 2014
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    Hi, will a higher inductance inductor effect a circuit rated for a lower inductance inductor, say for 12V operation we require 100uH, but for a 36V operation we need 150uH, do I have to build 2 circuits one for 12V input and one for 36V input or would the 36V input work with the 12V input.

    If inductors are like capacitors, then I'm guessing there'll be no problem.

    Please advise
     
  2. Kermit2

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    Feb 5, 2010
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    The circuit diagram is incomplete. there are no active devices shown nor any connection between the two power sources. the current changes from the series inductor will be delayed in relation to the voltage level changes, so the different vslues may be very important. without the whole circuit we can only guess if such a substitution is allowable.
     
  3. Chillum

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    Nov 13, 2014
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    HUH!? heres the veroboard layout for this circuit (traced with colour to show energy), maybe that'll help. Actives is shown by that Battery called Vout battery Vin is connected to LM2576 in pin 1 and output pin 2.
    I can assure you it works, I've built one. The square on the SIL5 pakage is pin 1, square is positive, and circle is negative, and square on the diode is the line on the package. VeeCAD is the software used switchingRegulatorColoursV2.png
     
  4. Kermit2

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    my apologies. i mistook the LM2576 for a 5 pin connector. (small viewscreen on this phone).
    the chances are good you will not have a problem with a single value inductor for both high and low voltage, test it out and see what you get with a 150uH instead of the 100. shouldnt see any change i would think.
     
  5. Chillum

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    thank you kermit2 that's what I hoped for, getting parts later this week then I'll report back with my findings
     
  6. ronv

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  7. crutschow

    Expert

    Mar 14, 2008
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    An inductor is not rated for voltage (except for the insulation breakdown voltage) but it is rated for maximum current before the core saturates. So it's the current rating of the inductor versus the maximum inductor circuit current that you need to be most concerned about.
     
  8. Chillum

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  9. Chillum

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    selected inductor for 36v circuit input; wanna use the same board for 12v, will that work?

    If I have to build 12V and 36V boards seperately, it's fine, I just need to know so I can place an order for 3A 100uH (which I can save money on if I don't need it!)
     
    Last edited: Dec 8, 2014
  10. ronv

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    What is the output voltage & current?
     
  11. Chillum

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    Nov 13, 2014
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    output voltage 36-2=34 variable to 1V input voltage 36 or 12 its the or part i'm worried about, If I build for 36, will it work for 12?
     
  12. ronv

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    I'm confused. :confused:
    You spoke of 12 volt and 36 volt input.
     
  13. Chillum

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  14. ronv

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    It's a buck regulator. You can't get 34 volts out with 12 volts in.
     
  15. Chillum

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    your'e not reading!
    INPUT 36 or 12
    OUTPUT 36-2=34 variable to 1
    34V out is obviously for 36V in, 12V in will OUTPUT less than 10
     
  16. ronv

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    Then why didn't you say that? :D
    To properly calculate it you need input, output voltage and current for each.
    What do you plan to do about the adjustment?
     
  17. Chillum

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    Nov 13, 2014
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    same circuit, but with 150uH and a 680uF Electrolytic C2 by the inductor
     
  18. ronv

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    You will be able to get a little over 1 amp out of it with 12 volts in and 10 volts out and a 150Uh. inductor.
    You should check the data sheet for your diode. It's to small.
    The voltage on the input cap is to low for 36 volt operation.
    R1 doesn't need to be so big. When the pot is set to a low value the output voltage will be low.
    http://www.ti.com/lit/ds/symlink/lm2576.pdf
     
  19. Chillum

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    Nov 13, 2014
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    please help me pick diode, fort777.co.za have 300v but no stock, Mantech I don't know what to pick 'cause those labelled fast is only 30V: http://www.mantech.co.za/Stock.aspx?Query=schottkyand

    EDIT Is the diode to be rated for output or input voltages?

    What do you gain with fast recovery, None of the 5 suppliers in the Cape (Cape Town) have fast recovery Schottky diodes rated higher than 30V fort777.co.za had one but it was discontinued so NOTHING. The table 1 has a normal side and a fast recovery side, why fast recovery when you can have normal, now I have to go with the 1N5822 because it's the only one I can get. Mean Well (the makers of my 36V PSU, says the V+ ADJ can get me down to 32V, for diode selection
    [
    B. The reverse voltage rating of the diode should be at least 1.25
    times the maximum input voltage.
    ]
    32x1.25=40, the rating on my diode, cutting it fine, but when working with such a low amount of components available, thats what I got
     
    Last edited: Dec 9, 2014
  20. ronv

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