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EL panel source

Discussion in 'Electronic Design' started by BOB URZ, Nov 3, 2004.

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  1. BOB URZ

    BOB URZ Guest

    I am looking for a good cheap source for generic EL panels for
    some older equipment retrofit. Has anyone done EL panel replacement? Can
    you just cut them down without damaging them?
    How critical is the voltage range to drive them?

    Bob
     
  2. Clarence

    Clarence Guest

    Sharp shears will cut them with little problem, but always measure to assure a
    clean separation between the elements.

    The voltage for most phosphors is about 85 to 135 Volts AC at about 400 to 800
    hertz. They will work on 60 hertz at a reduced output.
     
  3. It's also worth noting that the ones I use have the back conducting surface
    exposed, so you need to cover it with insulating tape or laminate the whole
    thing.

    Good advice from Clarence - I've made a couple that were short circuit.
     
  4. sPoNiX

    sPoNiX Guest

    Yes you can cut them down, however, their life is shortened, in some
    cases quite dramatically, due to the ingress of air.

    sPoNiX
     
  5. I didn't know that. Is this process prevented by laminating or is the
    damage already done at the cutting time?


    Gareth.
     
  6. John Fields

    John Fields Guest

    ---
    1. Good and cheap are sometimes mutually exclusive. How much do you
    want to spend, say, per square inch?

    2. I have.

    3. Usually.

    4. Not very. 90 to about 120VRMS will usually work OK. You can change
    the brightness by varying the voltage and the color (somewhat) by
    changing the frequency. Life to half-brightness varies inversely
    with brightness and with frequency.
     
  7. Clarence

    Clarence Guest


    Moisture!
    Perhaps I assumed too much.
    Seal the edge with a strip of clear plastic tape!
     
  8. NSM

    NSM Guest

    | I am looking for a good cheap source for generic EL panels for
    | some older equipment retrofit. Has anyone done EL panel replacement? Can
    | you just cut them down without damaging them?
    | How critical is the voltage range to drive them?
    |
    | Bob

    http://www.allelectronics.com have various of these, cheap.

    N
     
  9. John Fields

    John Fields Guest

     
  10. BOB URZ

    BOB URZ Guest

    Ok, the retrofit application i have has a display about 3/4" wide by
    4" long. Plastic encased like a laminated card. The EL display
    backlite is dead. Measuring the voltage with my fluke on AC scale measures
    about 55 volts AC. Is this too low for operation? It seems to be powered by a
    sealed step up module

    Bob
     
  11. NSM

    NSM Guest

    | Ok, the retrofit application i have has a display about 3/4" wide by
    | 4" long. Plastic encased like a laminated card. The EL display
    | backlite is dead. Measuring the voltage with my fluke on AC scale measures
    | about 55 volts AC. Is this too low for operation? It seems to be powered
    by a
    | sealed step up module

    Might be enough - tried 120 VAC on the strip?

    5" x 1" electroluminescent strip. Ivory in off-state. Glows green when
    energized by 120 Vac or inverter. For backlighting control panels,
    special-effects lighting, models etc. Solderable pins extend 0.2" beyond end
    of panel. CAT# EL-5 Your Price: $3.50 each

    http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=EL-5&type=store

    N
     
  12. Clarence

    Clarence Guest

    The EL is also frequency sensitive, since it IS a losey capacitor. If the
    frequency of the 55 Volts was higher than the usual 400HZ it might be enough. I
    have run El's on 50 - 75 V RMS at 1.8KHZ. Higher frequencies tend to have an
    affect the color.
     
  13. Terry Given

    Terry Given Guest

    Dont forget the type of fluke may be quite important - the waveform is
    in general not sinusoidal, and beware the frequency response of the
    meter. "When in doubt, scope it out." I invariably use a scope to see
    whats going on, and (where appropriate) a meter for the actual
    measurement. I've been caught too many times.....

    nowadays I use my trusty HP3400A 10MHz AC thermal RMS meter, which cost
    about US$50 - I miss those MIT junkfests on a sunday....

    I have never chopped one to pieces, but the contaminant issue sounds
    quite feasible. I last designed an EL backlight into a product 4 years
    ago - at the time I put a lot of work into ascertaining the lifetime,
    which is a strong function of temperature, voltage, frequency, sock
    colour etc. IIRC the backlites I was using were rated about 2,000 hours,
    and so I got the software to turn off the EL a few minutes after a
    keypress. I also designed a decent smps to drive the thing - the asian
    prefab EL drivers I looked at all had nasty waveforms, and were
    seriously crappy (appalling layout, beating bjts to death etc) as well
    as expensive and inconvenient to mount - which dies first, the EL or the
    smps.....

    Cheers
    Terry
     
  14. Bob Urz

    Bob Urz Guest

    2000 hours does not sound like a lot. What are the failure modes on a EL
    display? Its not like it has a filament that burns out

    Bob
     
  15. Clarence

    Clarence Guest

    The Phosphor fatigues and dims. Lower stress levels will achieve a longer live
    in some phosphors. However abt 5,000 hours is the most I've seen.

    The Asian drivers are basically a blocking oscillator, and the wave form is
    pretty distorted. However even a modified sine-wave-form will work and it
    doesn't affect the life enough to detect in a few hundred units I tested.
     
  16. NSM

    NSM Guest

    | The Phosphor fatigues and dims. Lower stress levels will achieve a longer
    live
    | in some phosphors. However abt 5,000 hours is the most I've seen.
    |
    | The Asian drivers are basically a blocking oscillator, and the wave form
    is
    | pretty distorted. However even a modified sine-wave-form will work and it
    | doesn't affect the life enough to detect in a few hundred units I tested.

    What about the EL night lights? Do they last longer?

    N
     
  17. They usually just lose brightness over time. The lifetime might be to
    50% of the original brightness.


    Best regards,
    Spehro Pefhany
     
  18. Clarence

    Clarence Guest

    Somewhat, since they are operating on 120 Volts 60 Hertz, but there is a broad
    specification for how much light is acceptable. EL Life is usually given when
    the light for a specified excitation results in half the original level of
    light. So in those terms NO, the night light doesn't last longer. But if you
    allow that the night light is useful at one quarter the initial light, then you
    might see 10,000 to 14,000 hours of it still lighting. Just not as bright.

    If the sealed Phosphor gets moist, with the seal broken, it will fail in a
    relatively short time.
     
  19. Terry Given

    Terry Given Guest

    I'd be pretty happy with 5,000 hours :)
    What I liked least about the blocking ocillators was the current spikes
    - they deliberately saturate the core, causing fairly high current
    spikes, then lay the circuit out on a single sided PCB in such a way as
    to maximise the loop area. Often they are truly rough on the
    transistors, which are generally the cheapest, shittiest transistors in
    existence - these things are mostly manufactured down to extremely low
    cost. I figured its a bit rough on the guy who spent $200,000 on his box
    of tricks to have the backlight shit itself because we used a $1 piece
    of junk to drive it.

    I forget what chip I ended up using (along with an smt L etc), it gave
    fairly sinusoidal waveforms, with nice low dV/dt, and ended up at the
    same cost as the nasty little blocking oscillator. Much lower profile
    though.

    Cheers
    Terry
     
  20. James Sweet

    James Sweet Guest


    I've cut them before with success.

    Try www.allelectronics.com for cheap surplus inverters to drive them.
     
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