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1.5v to 3.3v LED circuit

Discussion in 'Electronic Basics' started by LED Man, Feb 19, 2005.

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  1. LED Man

    LED Man Guest

    Looking to drive a white superbright led (1-4) from 1.5v to 2.5v
    battery, led requires 3.3v @ 20ma, is there a suitable small circuit, or
    single chip device

    TIA
     
  2. http://tinyurl.com/5843f

    --
    Regards,
    Robert Monsen

    "Your Highness, I have no need of this hypothesis."
    - Pierre Laplace (1749-1827), to Napoleon,
    on why his works on celestial mechanics make no mention of God.
     
  3. An NPN, a 1.5V AA battery, two resistors, a capacitor, a diode and a simple,
    hand-wound threaded toroidal. D2 can be a diode-connected 2N3904, a 1N4148, or
    a Schottky like a 1N5817-1N5819.

    V+ V+ V+
    | | |
    | | |
    | )|. .|( (about 50" of
    | )| |( magnet wire
    | )| T1 |( for both
    | + )| |( windings)
    --- | |
    - B1 | | D2 R2
    --- \ +---|>|---+---/\/\---,
    - / R1 | | 220 |
    | \ 2200 | | |
    | / | | |
    | | |/c Q1 | --- ~
    | '------| 2N3904 --- C1 \ / ~
    | |>e --- 100uF --- LED
    | (B1 > 1V) | | |
    | | | |
    gnd gnd gnd gnd

    It will drain a AA battery fairly completely, before quitting.

    Jon
     
  4. Jon...

    I have a hell of a time with ASCII schematics. Could you possibly post a
    "real" schematic to alt.binaries.schematics.electronic?

    Jim
     
  5. CWatters

    CWatters Guest

    copy into notepad and then format -> font -> "fixedsys"
     
  6. Rich Grise

    Rich Grise Guest

    You should be able to set your newsreader for a fixed font. I use
    Courier.

    Cheers!
    Rich
     
  7. I have Courier as my default font and I still have a hell of a time reading
    an ASCII schematic. Sorry.

    Jim
     
  8. Is it an inability to recognize the symbols?

    I guess I'm asking this because it took me exactly zero time to see and
    understand an ASCII schematic the first time I saw one and I've had very little
    trouble ever after, so I'm honestly curious about what makes this difficult for
    some -- I completely lack the personal experience to understand the trouble, so
    I'd appreciate any clues about what you perceive and don't perceive.

    Meanwhile, I'll try and load over a schematic in some format you can see. I
    have a few other things to take care of before I struggle with that, though.

    Jon
     
  9. Rich Grise

    Rich Grise Guest

    I'll have to throw in with petrus here, then. What's the hard part?

    Do your ASCII schematics not look like this one?:
    http://www.neodruid.net/images/ASCII_Art.jpg

    Good Luck!
    Rich
     
  10. No, they don't. The link you sent was quite readable. The schematic in
    this newsreader was highly compressed in the x dimension and absolutely
    unreadable. However, as I sit here and look, the fact that I've got my
    settings to Courier doesn't seem to make a difference. Just looking at this
    font I can tell it is a variant of Helvetica, or Arial, or whatever other
    san-serif font you want to call it.

    I need to do some more investigation as to why it looks like this. Or
    perhaps only the OUTGOING messages look like this...

    Thanks,

    Jim
     
  11. Lordy, Outlook Express makes you change the font in no less than THREE
    places in order to force messages to Courier. THe default fixed width, the
    default proportional width, and the little checkbox on the "advanced" tab to
    default all incoming messages to the default settings.

    Windoze does it again.

    Thanks for the help, Rich...

    Jim
     
  12. Lord Garth

    Lord Garth Guest

    If you use OE and the font is not set to default to a fixed width font, you
    can
    select 'view' then move down to 'text size' then move to 'fixed' to see it
    on the
    ASCII art on the fly.
     
  13. Clarence_A

    Clarence_A Guest

    GMAB
    Why bother to explain, He's a top poster, his inability to
    understand anything is clear. He thinks upside down! :)>)
     
  14. I really despise those who suggest that the 2N3904 is capable of doing
    this job adequately. With that wimpy transistor, you will be lucky to
    get enough current to power the LED at 8mA. Use a 2N4401 or the BC337.
    Or if you want to get a lot more current, try the 2SD965 or NTE11. If
    you can get some disposable flash cameras from your neighborhood
    drugstore or photo shop, the flash inverter uses this kind of
    transistor, and makes a great source for free transistors.

    The above circuit is okay, but since the LED _is_ a diode, you don't
    need the D2 and C2 filter cap, just connect the LED across the emitter
    and collector. And R1 will have to be lower, probably 1k, if you use
    something better than the 2N3904. The 2N3904 won't cut it with even a
    470, it'll just get hot and poof. And whatthe hell is R2 there for?
    That's just wasting power and ruining the efficiency!
     
  15. I'm actually using one and it's pretty decent on a white LED. If you have to
    despise me for it, I guess I can only hope to make it up some time later on.
    (I'm just a modest hobbyist, so I take corrections from just about anyone.)
    Fair enough.
    Actually, that's what I did before. In fact, I had no R2, as well. I just
    added those for tinkering, at some point, to smooth the pulses through the LED.
    Yes, I started out just as you say. Works just fine. This is what I'd started
    with:

    V+ V+ V+
    | | |
    | | |
    | )|. .|( (about 50" of
    | )| |( magnet wire
    | )| T1 |( for both
    | + )| |( windings)
    --- | |
    - B1 | |
    --- \ +---------,
    - / R1 | |
    | \ | |
    | / | |
    | | |/c Q1 --- ~
    | '------| NPN \ / ~
    | |>e --- LED
    | (B1 > 1V) | |
    | | |
    gnd gnd gnd
    (can be connected to V+, as well)

    Threading up the transformer on a tiny toroid is dead easy, too. By the way,
    I've picked up some small packages of them from a local electronics supply
    house, but I've not found a good web site that has them. Do you know of a good
    source for various ferrite toroids?

    Jon
     
  16. Excellent tip.

    If the reason we use ASCII Schematics is because of the text based
    USENET. Then why do some websites still use ASCII Schematics?
     
  17. Lord Garth

    Lord Garth Guest

    Leftover source material from the days of telnet perhaps...
     
  18. Rich Grise

    Rich Grise Guest

    Because if it works, don't fix it!

    Cheers!
    Rich
     
  19. Spajky

    Spajky Guest

    Italians with groups like this on their local ones
    like it.hobby.elettronica
    use interesting program to draw & see schematics for posting
    in text only usenet IMHO much bettter than ASCII ...

    its FidoCAD (maybe someone could write to the author to make an
    English interface & help file for it). Can be found here: less than
    1Mb installed:
    http://www.enetsystems.com/~lorenzo/fidocad_win.asp

    you draw a standard schematic, export it as text & paste it into a
    message like this (pasted code) interesting oscillator:

    [FIDOCAD]
    MC 85 45 0 0 580
    MC 70 45 1 0 170
    MC 50 55 0 0 170
    MC 50 45 0 0 120
    LI 85 45 60 45
    LI 60 55 85 55
    LI 50 45 45 45
    LI 45 45 45 55
    LI 45 55 50 55
    MC 45 65 0 0 045
    LI 45 65 45 55
    LI 100 45 100 25
    LI 100 55 100 75
    MC 100 25 3 0 010
    MC 100 75 1 0 020
    TY 105 15 5 3 0 0 0 * +6V
    TY 105 80 5 3 0 0 0 * -6V
    MC 105 30 0 0 170
    MC 105 65 0 0 170
    MC 120 30 0 0 045
    MC 120 65 0 0 045
    LI 105 30 100 30
    LI 120 30 115 30
    LI 105 65 100 65
    LI 120 65 115 65
    LI 110 50 135 50
    MC 140 50 0 0 075
    MC 145 50 0 1 075
    TY 60 60 5 3 0 0 0 * 2x 47nF
    TY 45 35 5 3 0 0 0 * 1mH
    TY 115 60 5 3 0 0 0 * 100n
    TY 115 25 5 3 0 0 0 * 100n
    TY 155 45 5 3 0 0 0 * 34kHz
    TY 75 35 5 3 0 0 0 * LM6181

    You to see it with that installed program, just copy that upper
    complete code, open the program, from menu open:
    modifica/incolla/come nuovo documento .... & so you see the
    schematics like usuall one; IMHO not a bad trick ... & easier than
    ASCII pics schematics ...

    Try it 4 fun ...
     
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