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LM338 Voltage and Power Questions

Discussion in 'Power Electronics' started by Electromotive, Mar 5, 2020.

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  1. bertus

    bertus Moderator

    1,172
    449
    Nov 8, 2019
    Hello,

    That is a nice build you made.

    As @Bluejets said, the TO3 has better thermal properties:

    LM338_electrical.png

    If you want a beefier regulator with a lower drop-out voltage, have a look at the LT1083.
    That is capable of 7.5 A, with a drop-out voltage of about 1 Volt.

    Bertus
     

    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,614
    2,372
    Nov 17, 2011
    Just one note: Your schematic shows the primary side fuse opposite to the mains switch.
    Afaik in the US the mains outlets have dedicated positions for live and neutral. To increase safety both fuse and switch should be in the life wire. This way the switch will separate the power supply from live as will the fuse do in case of overload. In both cases it is less risky to have the rest of the power supply being connected to neutrral.
    Whereas in your schematic if the fuse is triggered, the other side of the power supply's input is still connected to life. But you will not be aware of this possibly dangeroues situation because the neon lamp will be off and the supply will show no output.
    This should be an easy change to your otherwise great looking build.

    See here and here.
     
    Martaine2005 likes this.
  3. Electromotive

    Electromotive

    38
    4
    Feb 14, 2018
    Yes, I agree but: I found the TO3 to be unobtainable unless I wanted Bulk for too much money. I tried the oversea's versions and had issues. Settled on the Lesser TI made ones I could find. Thank you... Tom
     
  4. Electromotive

    Electromotive

    38
    4
    Feb 14, 2018
    You caught me. The lamp is a 110V neon and is on the mains side..Duhhh.... Thanks...Tom
     
  5. Electromotive

    Electromotive

    38
    4
    Feb 14, 2018
    The Difference between pure regulated DC and Digital output. Interesting... IMG_20200505_150640288.jpg

    IMG_20200505_150330964.jpg
     
  6. Electromotive

    Electromotive

    38
    4
    Feb 14, 2018
    Sorry, a little confused here. My fuse is connected to the mains hot line via a non reversible 110 volt plug. If the fuse blows, the hot line is disconnected. Can you show me a schematic of what you are describing as a better way to be safe? Thank you... Tom
     
  7. Bluejets

    Bluejets

    4,296
    912
    Oct 5, 2014
    Actually, any portable device run on a lead and plug should use double pole switching as there is never any certainty whether an outlet or the plug is correctly wired.
     
    Harald Kapp likes this.
  8. Bluejets

    Bluejets

    4,296
    912
    Oct 5, 2014
    This may be true but if this is the case, switching only the neutral is not allowable.
    See #27.

    If the unit is hardwired ,(permanently wired into the house wiring system) single pole switch is allowed but then the switch must be in the active conductor.
     
  9. Electromotive

    Electromotive

    38
    4
    Feb 14, 2018
    I have the switch located on the hot line, the one with the Hot oriented prong plug. The schematic is not drawn correctly, as I referred to in my first response but not precisely communicated.
     
  10. Harald Kapp

    Harald Kapp Moderator Moderator

    10,614
    2,372
    Nov 17, 2011
    Please provide a revised schematic, To me it is by now totally unclear where switch and fuse are located with respect to mains and neutral:(
     
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