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LED Flasher

Discussion in 'Misc Electronics' started by Jim Thompson, Aug 16, 2003.

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  1. Jim Thompson

    Jim Thompson Guest

    I was sitting here amusing myself this afternoon pondering how *I*
    would design a high efficiency LED flasher.

    The result may be seen at LED-Flasher-2.pdf on the S.E.D/Schematics
    page of my website.

    I didn't have a 3V LED model available but, since the circuit doubles
    the rail voltage, it should easily drive a 3V LED with a 3V supply.

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | [email protected]_innovations.com Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    For proper E-mail replies SWAP "-" and "_"

    I love to cook with wine. Sometimes I even put it in the food.
     
  2. Mark Jones

    Mark Jones Guest


    Is it too much to ask for the theory of operation? Is the IC a
    schmitt-trigger?
     
  3. That's the biggest heap of chips I've ever seen to blink an LED and it's
    not even efficient! It's worse than the old LM3909.

    If you want to go nuts with chips, at least use a flyback booster. You
    can even bootstrap the boosted LED voltage to drive the PWM circuit,
    allowing operation down to a few mV after a starting threshold is
    reached.
     
  4. So show us a circuit. The one thing I don't care for is the
    LMC67whatever it was that is probably hard to find. Other than that,
    it looks a bit like Dave Johnsion's flashers at
    http://www.imagineeringezine.com/e-zine/hcircuits.html#LED Circuits.


    --
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    ###Got a Question about ELECTRONICS? Check HERE First:###
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    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
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  5. Ian Stirling

    Ian Stirling Guest

    Hmm.
    Bit bulky.
    Currently pondering my design for a flashlight/compass/key-finder.
    Take a bit of sapphire a centimeter and a half in diameter, and 5cm or
    so long. Facet the outside a bit to knock the corners off and add a little
    sparkle.
    Now bore a hole and take a rod of sapphire of the appropriate size, and
    carve it to accept a few dice of varying colours, which are run at an average
    current of a few microamps, and pulsed every 30 seconds for a few milliseconds.
    The battery is inside a decorative 'totem pole', and all covered by a
    stainless/silver cap.

    The flashlight is triggered (I think, design work continues) by a sharp knock.

    Recharging happens due to a tiny bit of solar cell incorporated into the cap,
    which is charged by an optical charger. (or sunlight)

    This was triggered after seeing a nice bit of sapphire on ebay.
    (pale blue)

    Battery a 1/3 NiCd AAAA probably.
     
  6. Jim Thompson

    Jim Thompson Guest

    Re-posted to the site with vagaries fixed and some 60 second data.

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | [email protected]_innovations.com Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    For proper E-mail replies SWAP "-" and "_"

    I love to cook with wine. Sometimes I even put it in the food.
     
  7. Jim Thompson

    Jim Thompson Guest

    Like I say, I was just 'musing myself... but does the real part "die"
    at +2.7V? The published model is still working at +2V. My experience
    with CMOS says they'll usually work down to 2*VT and sometimes lower.

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | [email protected]_innovations.com Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    For proper E-mail replies SWAP "-" and "_"

    I love to cook with wine. Sometimes I even put it in the food.
     
  8. Jim Thompson

    Jim Thompson Guest

    I'll look up the Maxim part and place it in the circuit.

    (You may note that I can now emulate parts with 8, 14, or 16-pin, or
    whatever, representations, and call the equivalent SUBCKT ;-)

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | [email protected]_innovations.com Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    For proper E-mail replies SWAP "-" and "_"

    I love to cook with wine. Sometimes I even put it in the food.
     
  9. I have a question along this same line. On Dave Johnson's
    http://www.discovercircuits.com/PDF-FILES/hourmtr.pdf, he has an hour
    meter that uses a CMOS inverter as an amplifier. He shows the output
    tied to input with a 22 Meg resistor, to make it linear. He claims
    the whole circuit uses only 2 microamps, which seems low to me. I
    think that the CMOS chip would draw more than that because it's
    biasing itself right in the middle, halfway between + supply and
    ground. The supply voltage is 3VDC. The inverter is a 4069B.
    I don't have one laying around to try and see if it's really true.

    --
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    ###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]@@
     
  10. Jim Thompson

    Jim Thompson Guest

    A 4069B is old-style high-voltage CMOS. At 3V rail you are probably
    at or below 2*VT, thus low consumption.

    Since my simulation uses a device-level model (*not* behavioral) I
    just re-checked the results and zoomed in to the LMC6762 current... At
    V+ = 2V, I(V+) is nominally 10.25uA, pops up to 1.7mA at the start of
    the capacitor dump but has fallen back to 10.25uA before the cap is
    half dumped. Average power consumption of the whole contraption is
    150uA at 2V, 250uA at 3V.

    At 2V operation I'm smacking the LED with 6.7mA, decaying in 225ms.
    I've haven't played enough with LED flashers to know how long the
    duration needs to be to be noticeable.

    From my LMC6762 data sheet, the fall-off of current seems to occur
    below 2.2V unless you're fond of -40°C ;-)

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | [email protected]_innovations.com Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    For proper E-mail replies SWAP "-" and "_"

    I love to cook with wine. Sometimes I even put it in the food.
     
  11. [ ... ]
    : ... unless you're fond of -40°C ;-)
    :
    : ...Jim Thompson

    The neat thing about 40 below is that it's the same in °C or °F ;-)
     
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