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Dropping 1V from a Regulated 6V Wall Wart

Discussion in 'Electronic Repair' started by Watson A.Name - Watt Sun, Dark Remover, Dec 29, 2003.

  1. I read in alt.binaries.schematics.electronic that Watson A. Name - Watt
    >) about 'Dropping 1V from a Regulated 6V
    Wall Wart', on Wed, 31 Dec 2003:
    That's a coaxial connector, a bit like a phono plug but with a smaller
    centre pin. Is that what you have?
    I'd forget those descriptions if I were you. Certainly the Belling
    connector has very little indeed to do with PAL. It is the subject of an
    IEC standard - IEC 60169-2.
     
  2. Hmm, a complementary-darlington emitter-follower transistor would
    be less sensitive to changes in load current:

    : +6.0V, from wall wart
    : >--+--------+------+
    : | | |
    : | 220 | Q1 2sa1011
    : | | |/E pnp TIP32
    : | +----| etc
    : | | |\
    : 1.0k |/ |
    : pot <---| Q2 |
    : | |\E npn |
    : | | |
    : 7.5k +------+-----> + output
    : | to load
    : - >--+---------------------> -

    Here the Q2 voltage drop is much more predictable, because it has a
    relatively steady current set by Q1's base-emitter resistor, which
    has about 0.55 to 0.75V across it despite output load changes. The
    Q2 current is about 3 - 5mA and we expect a Vbe drop of about 700mV.
    The lower end of the pot sits at about 5.3 volts.

    The most serious problem with this circuit is its complete reliance

    Watson A.Name - Watt Sun, Dark Remover asked:
    No, it's an ordinary regulator, using Q2's Vbe (roughly 0.7V) as a
    voltage reference. The pot as shown would be a poor choice because
    valid adjustments would only use a small part of the pot's range.
    No doubt nospam knew that and was just simplifying his drawing by
    using one part instead of three. This should work; the top of the
    pot has about 0.82V when the regulator is calibrated for 5V out:

    This circuit has several problems. The tempco of Vbe is bad, but
    the uncertain current through Q2 an even worse problem. This is
    because the voltage difference between the +6V input and Q1's base
    is small (and may vary widely), and Q1's base current is unknown.
    If Q2's current changes by a factor of 10, its Vbe will change by
    about 60mV, or nearly 10% of its value. As a result Q2 makes a
    poor voltage reference in this circuit, even if manually adjusted.
    A big cap is fine, maybe even necessary in that location, because a
    small output cap could make the feedback loop unstable. We discuss
    this issue in AoE and call it brute-force compensation.

    The current won't go backwards for several reasons. The wall wort
    probably doesn't draw output terminal current when the AC is off.
    If it wanted to, Q1's Veb breakdown would certainly be above 5V so
    no current would flow anyway.

    Jim Thompson wrote...
    This is a much better approach, using TL430's 2.75V reference with
    a built-in error amplifier. The more popular TL431 can be used with
    its 2.50V ref if the feedback-sensing resistors are the same value.

    But I'm not happy with the output emitter follower in the circuits
    above, because the low Vin - Vout difference leads to such widely-
    varying currents through the control element. Perhaps my circuit
    can be combined with Jim's circuit:

    : +6.0V, from wall wart
    : >--+------+------+
    : | | |
    : | 220 | Q1 2sa1011
    : | | |/E pnp TIP32
    : 750 +----| etc
    : | | |\
    : | |/ |
    : +----| Q2 |
    : | |\E npn |
    : | | |
    : | +---+--+----> + output
    Thanks,
    - Win

    whill_at_picovolt-dot-com
     
  3. Winfield Hill wrote...
    I'm still not happy with the poor dropout-voltage capability of
    this circuit. It should be able to operate with Vin much closer
    to Vout. Aha! Simply adding a diode and resistor lets us reduce
    the dropout voltage down to near the saturation voltage of Q1.

    : +5.3 to 9V
    : >--+-----+------, SIMPLE 5.0V REGULATOR
    : | | |
    : | 220 | Q1 2sa1011
    : | | |/E pnp TIP32
    : 470 o----| etc
    : | | |\
    : | |/ |
    : o---| Q2 '----o----> +5.0V
    : | |\E npn | output
    : | | | to load
    : | | 1n4148 |
    : | '--o--|<|---o
    Of course, an even more simple circuit is possible, using one
    of the many low-cost low-dropout three-terminal regulator ICs.

    : +5.3 to 9V etc
    : >-------, EVEN MORE SIMPLE 5.0V REGULATOR
    : __|__
    : | |
    : | |---+---> +5.0V
    : |_____| _|_ output
    : | --- to load
    : | |
    : - >-------o------o---> -

    But this circuit isn't as much fun. :>)

    Thanks,
    - Win

    whill_at_picovolt-dot-com
     
  4. This alt 0233 --> é looks to me like it's an accented e, as in Jose'
    What's it look like to you?

    --
    @@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@,@@[email protected]@[email protected],@@[email protected]@[email protected]@[email protected]@
    ###Got a Question about ELECTRONICS? Check HERE First:###
    http://users.pandora.be/educypedia/electronics/databank.htm
    My email address is whitelisted. *All* email sent to it
    goes directly to the trash unless you add NOSPAM in the
    Subject: line with other stuff. alondra101 <at> hotmail.com
    Don't be ripped off by the big book dealers. Go to the URL
    that will give you a choice and save you money(up to half).
    http://www.everybookstore.com You'll be glad you did!
    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
    @@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@
     
  5. Active8

    Active8 Guest

    On Wed, 31 Dec 2003 14:29:34 -0800, Watson A.Name - "Watt Sun, Dark
    An e with a single dot over it, not the accent mark as in Jose'. I
    think it's one of those pronunciation symbols.
     
  6. Active8

    Active8 Guest

    It looks (the outer part) exactly like one of those RS push on F
    connectors - the male one (male center conductor, female housing)
    but the center conductor is hollow and split as if the mating
    connector would compress it and cause it to seize the mating
    connector's center conductor which in that case would make the CIQ
    (connector in question) female and female no thread. I couldn't
    quite get a real idea of the size from the photo. Let's check
    Pasternack.

    The PAL connector in this book is a push on, but the CIQ can't be
    this PAL connector. The one I'm looking at is male-female into
    female-male with the male housing (which would correspond to the
    CIQ) is .370" OD.

    I see 75 ohm MCX connectors where the jack corresponding to the CIQ
    accepts a plug with a .147" OD housing - seisure and all.

    I'd replace the friggin' thing with something I can lay hands on
    easily. F connectors are common enough. Push ons I only use for
    testing.
     
  7. Active8

    Active8 Guest

    On 31 Dec 2003 14:00:52 -0800, said...
    Now, did you do this years ago and just walk through the thought
    process for the benefit of the group, kinda like the "Now Read This
    Article and Burn it." article, pulling a rabbit out of your hat to
    the awe of the crowd? :) or what?

    Happy New Year and best of health.

    Mike
     
  8. Fred Bloggs

    Fred Bloggs Guest

    If you want a 1V drop (for some reason???) then something like this:


    Please view in a fixed-width font such as Courier.


    LM185-ADJ
    \
    +---------|< |---------+
    | \ | |
    | +------+-------------------------+
    | | | |
    | / | |
    | 470 | |
    | / | |
    | TIP42 \ | |
    Vin----+-------- e c ---+-------+----------------------->Vout
    | \ / | | |
    | --- | | c
    | 10K | 1N4148 | | 10K |/
    +----/\/\---+---|>|----+ +--/\/\-----+---|
    | | |\
    | c e
    | \| |
    | |---+
    | /| |
    / e /
    470 | 1.3K
    / | /
    \ | \
    | | |
    --- --- ---
     
  9. I read in sci.electronics.design that Active8 <[email protected]
    The dot instead of a proper accent is a feature of whatever font you are
    using. Look at it in Courier, Arial, Times New Roman.
     
  10. I read in sci.electronics.design that Active8 <[email protected]
    You've described a Belling coax connector, I think. I don't know what
    Pasternack is; a connector distributor?
    I just don't recognize the term 'PAL connector'.
    You should be able to get Belling-type connectors from Farnell/Newark.
     
  11. Active8

    Active8 Guest

    Uh, sorry. It's pretty much the same in all three. The problem is,
    at this high screen res it looks like a dot when in fact it's a
    small slash.

    Hey. If you ever have that prob (I use high res to make room for
    large CADs so other apps without zoom are screwed) there a little
    toy called Screen Loupe you can get. It's like having a magnifying
    glass you can drag around the screen like a sceen color picker or
    screen tape measure. Glad I remembered.
     
  12. Active8

    Active8 Guest

    On Wed, 31 Dec 2003 14:29:34 -0800, Watson A.Name - "Watt Sun, Dark
    ------------------------
    Hey Watson. You accidentally typed alt 0233 as you said instead of
    alt 0223 like John said :)

    Also, measure your connector & see if that MX 75 O [ <== this
    little omega looks like a zero. arrrggghhh! No HTML in NNTP
    either.]

    connector I posted the OD on is close. And if you look back to the
    link I posted on these extended ascii codes and other useful (?)
    links, you'll see a connector reference link near the top.
     
  13. Active8

    Active8 Guest

    Yes. www.pasternack.com It seems like they replace my catalog every
    month. They have a UK disty: www.spectech.dial.pipex.com
    I thought PAL was/is (it is) a Europeeeen video standard. But there
    is a PAL connector in the cat sure enough and it ain't what
    Watson's got.
    That's a good source for a lot of stuff. In Baltimore there's
    Bainsville Electronics which is great, but I've only seen gold-
    plated *kits* in the showcase. I'd wager they have it though.
     
  14. mike

    mike Guest

    My mistake. I read the subject line and the first line of the post
    and mistakenly concluded that you wanted to use a regulated wall wart.
    My baad.
    mike
     
  15. I read in sci.electronics.design that Active8 <[email protected]
    Indeed it is; it's the whole phrase 'PAL connector' that I don't
    recognize.
     
  16. Rich Grise

    Rich Grise Guest

    Hmm. When I hit alt-0233, I get one of these: !

    Cheers!
    Rich
     
  17. Active8

    Active8 Guest

    I can say with cetainty that I received an exclaimation point.

    Hopeless?

    Maybe not. If what I received is what you sent then the same code
    is displaying the same character on the screen on both ends. JW and
    I seem to have the same settings (odd because he said he used
    winders 98), but you either have your locale set differently or
    something I haven't though of.

    I'm set for English(United State) - Regional and Language settings
    in control panel.

    Character map isn't working here for omega so I'd better blow it
    off.
     
  18. Jim Thompson

    Jim Thompson Guest

    alt-0233 = é with NumLock ON or OFF, Win2K machine

    ...Jim Thompson
     
  19. James Sweet

    James Sweet Guest

    Don't type the leading zero unless it's a 2 digit code, ASCII codes are all
    3 digit from 000 to 255.
     
  20. [snip]
    Yeah, but I've got four or five of them and I didn't want to crack
    them open and then have to deal with the hassles of a case that's no
    longer solidly sealed. And besides, they were only two bucks apiece.
    I may bave paid more for their shipping.

    Also, I bot four of the 6VDC unregulated wall warts at the same time,
    and they have about 7 or 8V output unloaded. I don't think they have
    enough voltage to allow a 7805 to work properly, at least not up to
    200 mA, because the DC voltage drops down to near 6V at that current.

    But 6VDC is a convenient value, used by a lot of equipment that has
    four AA cells. So I have them just in case I want to 'electrify' one
    of those ol' radios or whatever.

    --
    @@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@,@@[email protected]@[email protected],@@[email protected]@[email protected]@[email protected]@
    ###Got a Question about ELECTRONICS? Check HERE First:###
    http://users.pandora.be/educypedia/electronics/databank.htm
    My email address is whitelisted. *All* email sent to it
    goes directly to the trash unless you add NOSPAM in the
    Subject: line with other stuff. alondra101 <at> hotmail.com
    Don't be ripped off by the big book dealers. Go to the URL
    that will give you a choice and save you money(up to half).
    http://www.everybookstore.com You'll be glad you did!
    Just when you thought you had all this figured out, the gov't
    changed it: http://physics.nist.gov/cuu/Units/binary.html
    @@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@
     
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