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Forever Flasher (& flashlight)

Discussion in 'Electronic Basics' started by Watson A.Name - 'Watt Sun', Aug 3, 2003.

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  1. I built the flasher circuit from Dave Johnson's website, See URL
    http://www.discovercircuits.com/PDF-FILES/3vledfs1.pdf
    But it just went full on, wouldn't flash. So I had to put a 2.2k from
    Q2 base to emitter to get it to flash. I also used two 0.1 uf ceramic
    caps instead of rhe 0.68 uF, and the flash rate is right around 1 Hz.
    The peak current is 17 mA, and average current is about 100 micromps
    at 3V.

    I then connected it to a 3V photovoltaic cell and a 1N4148 to prevent
    the current from going back into the photocell, and a 6800 uF
    capacitor to store the current generated by the light. I put the
    photocell directly under a light bulb, and it works fine, and it keeps
    working for less than a minute when the light is turned off. So now I
    need a lot bigger capacitor, something that will run it for a coupla
    hours.

    I'm thinking that it would work good using a pair of 1 F, 2.0V
    supercaps in series, charged by the photocell.

    I bought a Forever Flashlight, the one that has a single white LED,
    with a magnet and coil in the barrel that charges up a supercap when
    it is shaken. It works, but I'm disappointed in the light output.
    The instructions say to shake it for 90 seconds, but even longer than
    that gives the LED only a few mA, not a really decent amount. It has
    a lens to concentrate the LED's light, so it's better than just the
    bare LED alone. Obviously it's meant to be used for situations where
    a regular flashlight might not be working, like in an
    emergency/earthquake preparedness kit. The body of the flashlight is
    clear plastic so I can see the parts inside, and there's a supercap in
    there, but the plastic is too thick to see the value, which is
    blurred.

    So I'm wondering if I should order a couple of these supercaps. The
    solar cell is rated for 3V at 40 mA, see the SPL-60 on All Electronics
    website, http://www.allelectronics.com/cgi-
    bin/category.cgi?category=565&item=SPL-60&type=store
    It puts out an honest 4V in bright sunlight, so I would think that it
    will charge two 1 F supercaps in series in a few minutes. 3 TCs at 40
    mA would be 38 seconds, roughly. Maybe I should try for a couple
    farads to keep it running all night long. Has anyone done this
    before? Do these supercaps have low enough leakage to stay charged up
    for a half a day? After seeing their performance in the 'Forever'
    Flashlight, I'm not so sure.

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  2. dan williams

    dan williams Guest

    it looks like you could use a peak at Elna's catalog,

    Their 100F capacitor (I'm picking the biggest one because I can) rated
    at 2.5V
    charts out to run for about 200 seconds at 50mA (I'm taking this at a
    1.5V cutoff,
    use a switching (buckboost) led controller and get more. especially if
    you are useing
    more than one with a supply of 4V. I dont know what elna's 100F
    capacitor costs. I imagine
    its not cheap.

    CATALOGS! I must have more catalogs! HA, HAHAHAHAHA!

    Dan


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  3. See if you can find one of those "wind up" flashlights. Similar to the
    Freeplay radios. That seems to be better technology in terms of time
    spent winding vs illumination time. I've seen one with a selectable
    xenon mode (runs charge down fast) or 3 white LEDs (less light for much
    more time).
    If a while LED uses 20 mA, then a 40 mA PV cell will give you 2 minutes
    of run time for each minute of charge time (ignoring losses and lots of
    other things). If you fully charge the supercaps in 38 seconds, you'll
    only get about twice that running time. Add super caps (and $$) to get
    more time.

    You might be better off looking for some DC-DC converters, NiMH charging
    controllers, etc. and using as many mAh of battery capacity as you need
    for your design illumination time requirements dictate.
     
  4. Er, the flasher takes about 100 microamps. That means that it should
    run maybe 400 times longer than the charging time, something less than
    4 hours. I guess I could parallel a second pair of 1 Fs to give a
    total of 1 F at 5VDC. That should give a flash time of several more
    hours. I can't say because I don't know what the cutoff voltage is
    for the flasher.
    Batteries go bad, I want to have a forever flasher, not a 5 year
    flasher. That's why the 1 F supercaps.


    --
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    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. Tim Williams

    Tim Williams Guest

  6. Ian Stirling

    Ian Stirling Guest

    Lithium D cells are $20 (US) or so, and have a capacity of around 20Ah.
    This would run the flasher for around 200000 hours, or around 22 years.
    Add a light sensitive switch, and you can probably extend this a bit.
    And you can leave off the solar cell too.

    A couple of NiCd AA cells would probably run it for around 6 months, after
    a full charge.

    (this is probably around the right draw, they'll self-discharge in around a
    year in most climates anyway)
     
  7. Here's the URL for one of the schematics of the inverter. This one
    says it works down to .4V, there are others on his website.
    http://www.belza.cz/ledlight/m2d.htm

    I was thinking of putting the circuit and solar cell in a clear epoxy
    block. I've done it before by pouring a thin layer, and arranging the
    working circuit, then pouring another thicker layer over that. Trick
    is to get rid of the bubbles. So using a 5 year rechargeable battery
    is not an option. I would consider using rechargeable cells if it was
    in a package with a battery holder. But I've already got one of
    those. ;-)

    I checked out the eBay URL, but it's not clear to me how many LEDs are
    in the package. It says 100 pcs but in the pic looks like it's a lot
    less. And the 'buy it now' price is a bit on the low side for that
    quantity. So I'm not sure if I'd buy them. Another factor that
    bothers me is that any time one buys LEDs at cut-rate prices, there is
    a very high likelihood that they're seconds or rejects. I've
    purchased low priced LEDs that have flaws in the lens, or that are not
    centered properly in the epoxy package, etc. I've done very well by
    buying from Nichia or from Wilcoxson's www.whitelightled.com. Also,
    you can buy Yoldal LEDs that are similar from
    http://www.8000mcd.com/catalog.html but I haven't bought any from
    there, so I can't vouch for the quality.

    So, has anyone purchased some of those eBay LEDs?

    --
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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
    @@[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]@@
     
  8. Forever isn't 6 months, nor 5 years, nor 22 years. Thanks, but I'd
    really like to get the info I asked for on the 1 F supercaps.

    BTW, I have a 1 LED flasher that runs off four AA 2000 mAh Ni-MHs, and
    it lasts for about a month, maybe a little more. I don't know what
    the peak current thru the blue LED is, but it's very bright. Maybe
    two flashes per second. I've noticed the Ni-MHs lose some of their
    capacity sitting around for a month or three. But that's just a
    guesstimate.

    If I pot a clear epoxy case of the LED in clear eopxy, what does it do
    to the beam pattern? Suddenly the index of refraction is the same as
    the lens, so it isn't a lens any more. POOF! The beam goes wide
    angle, I would guess. Maybe I'll have to dunk a couple LEDs in a
    glass of water to see what happens!

    --
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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
    @@[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]@@
     
  9. Ian Stirling

    Ian Stirling Guest

    I would not be very certain that the supercap would still be working
    after 20 years.

    Why do you want 'forever'?

    Ni-MH have a very bad self-discharge rate, especailly in high temps.
    You may well find NiCd better.
    Pretty much.
     
  10. Leave

    Leave an air space in front of the LED lens to reduce that problem.
     
  11. Jim Thompson

    Jim Thompson Guest

    Good idea! Probably ought to try to keep the epoxy with co-planar
    surfaces also.

    Or, better yet, pot with the LED lens sticking clear thru the
    encapsulation.

    ...Jim Thompson
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    For proper E-mail replies SWAP "-" and "_"

    Why is it that Democrats can't debate politely?
    And are only rude and interruptive.
    Lack of mental capacity?
     

  12. Sorry about that. I thought you were trying to apply the supercaps to
    the flashlightapplication, not the flasher.
     
  13. Yeah, wacky is the right word. I checked the flickering LED circuit
    and it looks like the values for the caps and Rs in the oscs aren't
    right. But you _have_ to resave that gawdawfully huge delayed off
    switch .PNG to 1024 by 768 size. The 6600 pixels wide is ridiculous!

    The solar engine doesn't seem to do anything other than store up and
    release the charge in the capacitor. I'm not sure how this would help
    my situation.

    The LED flasher is a V boost circuit. We've already been thru a few
    of those here in ABSE and the other sci.electronics ngs. I checked
    that ferrite bead on both Digi-Key's and Mouser's website and it's
    just a tiny thing. I can't figure how you could pass that many turns
    of even fine wire thru the center hole. The only way I can see how
    you'd do it is to wind the wire around the outside like a regular
    bobbin. Even then the thing is going to be tiny, with really fine
    wires. And I don't believe this has 120 uH inductance (nor 120 mH, as
    it says in the text).

    Anyhoo, this circuit is kewl for 1.5V stuf, but I've already got 3 or
    4V from my solar cell, so no problem. It runs the flasher okay. It's
    just a matter of pulling in enough charge from a few minutes in direct
    sunlight, where the LED can't be seen, and then once the cap is
    charged, bring it inside where it can flash for hours. Or it could be
    set near a window to charge up and as the sun sets, it continues to
    flash for hours. That's why I need the 1F or so supercap and some
    info on how they work in this kind of circuit.

    I bought some already wound inductors from Mouser, and they work good
    for the inverters I made. It would be easy to just wind a few turns
    of #28 or finer wire around the outside of the bobbin of this inductor
    to give a feedback tickler coil like the one you made. I like already
    assembled coils because of repeatability factors and just plain time
    savings.


    --
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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]@@
     
  14. Ban

    Ban Guest

    If I pot a clear epoxy case of the LED in clear eopxy, what does it do
    If you stick that solar cell in clear epoxy it will fail after short time
    because of different thermal expansion. (done that, that's why I say that)
    Rather take some silicon based potting and glue the cells on top only. Then
    use a frame with a plastic or glass inlet to protect the cheap cells from
    humidity.

    ciao Ban
     
  15. Ian Stirling

    Ian Stirling Guest

    Silicon is a hard substance that is used to make solar cells.

    Silicone is a polymer that's used to make everything from flexible tubing
    to sex toys.

    --
    http://inquisitor.i.am/ | mailto: | Ian Stirling.
    ---------------------------+-------------------------+--------------------------
    "I meant, have you ploughed the ocean waves at all?" Colon gave him a cunning
    look. 'Ah, you can't catch me with that one, sir' he said 'Everyone knows
    horses sink' -- Terry Pratchett - Jingo
     
  16. Now you've _really_ ruined my day! Y'see, the solar cells _already_
    come from the factory mounted in clear epoxy! Now what am I gonna do?
    Are they going to fail when I put them in the sunlight? :-(

    But since they are already coated with epoxy, I can assume that
    potting them in an epoxy block will not do any more harm. Am I right?

    --
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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]@@
     
  17. Ban

    Ban Guest

    Are you sure that this is epoxy and not some other more flexible stuff? I
    tell you I had some(33) Siemens 6" monocrystalline cells. They were coated
    with some whitish epoxy-like material on the back. to combine them i poured
    some epoxy mixed with these small glassballs and the hardener only on the
    back, the front was a special glass. The assembly worked for one year, but
    when left in the hot sun for some time, there were cracks all over the
    individual cells, I had to throw everything. :-((
    I then inquired and found out about my mistake. The Siemens guy told me that
    this coating is really the most difficult part of the game.
    I do not know about polycristalline or amorph cells, but the monocrystalline
    cells are utterly brittle and damaged easily.
    removed irrelevant x-posts
    ciao Ban
     
  18. Ban

    Ban Guest

    Are you another self appointed apostrophe inquisitor or what? There is
    already one in this group. But maybe in holydays.

    thanks for the correction Ban
     
  19. Ian Stirling

    Ian Stirling Guest

    Sorry, it's just a pet hate.
    :)
     
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