Increasing EL inverter drive power

[bitrex]

Not sure if the EL material I have available is less efficient than how
it used to be back in the day, but this inverter circuit:

<https://imgur.com/a/8dOxe1R>

Can't drive some replacement EL material (the material tends to itself
fade out with time) I've put under the LCD display to very decent
brightness. It's too dim under room lighting.

Power is 5V supplied bottom right, I'm assuming the small xfmr is wound
like an autotransformer with taps? The circuit is pretty insensitive to
component changes, almost any small-signal NPN seems to work, reducing
C18, R1, R2 by half has little noticeable effect other than slight psu
draw increase. Oscillation freq stays about 800 Hz.

Raising supply voltage to 6, 7, 8 volts increases brightness,
oscillation freq stays about the same, whine from the inverter starts to
become objectionable.

If the oscillation frequency and power output is mostly determined by
the characteristics of the transformer I guess I'm SOL.

 

[bitrex]

On 10/13/19 7:25 PM, bitrex wrote:

Not sure if the EL material I have available is less efficient than how
it used to be back in the day, but this inverter circuit:

https://imgur.com/a/8dOxe1R

Can't drive some replacement EL material (the material tends to itself
fade out with time) I've put under the LCD display to very decent
brightness. It's too dim under room lighting.

Power is 5V supplied bottom right, I'm assuming the small xfmr is wound
like an autotransformer with taps? The circuit is pretty insensitive to
component changes, almost any small-signal NPN seems to work, reducing
C18, R1, R2 by half has little noticeable effect other than slight psu
draw increase. Oscillation freq stays about 800 Hz.

Raising supply voltage to 6, 7, 8 volts increases brightness,
oscillation freq stays about the same, whine from the inverter starts to
become objectionable.

If the oscillation frequency and power output is mostly determined by
the characteristics of the transformer I guess I'm SOL.

The "squeal" from these inexpensive off-the-shelf EL wire/tape inverters
you can buy for Halloween costumes and stuff is revolting!

<https://www.ellumiglow.com/electroluminescence/el-inverters/el-wire-inverters/electric-optics-middy-el-wire-inverter-powers-10-16-25-feet>


I have one on the bench driving a five foot section of EL wire from the
recommended 12VDC supply and in a quiet house I can hear it whining 30
feet away. irritating high-pitch racket

Has nobody figured out how to make an inexpensive inverter for this
stuff that's shushie?

 

[Winfield Hill]

bitrex wrote...

If the oscillation frequency and power output is mostly
determined by the characteristics of the transformer ...

In my experimenting with EL panels, years ago, I found
they're sensitive to the operating frequency. I don't
think you can make major changes, such as going above
20kHz, and have them still work OK.


--
Thanks,
- Win

 

[Robert Baer]

Winfield Hill wrote:

bitrex wrote...

If the oscillation frequency and power output is mostly
determined by the characteristics of the transformer ...

In my experimenting with EL panels, years ago, I found
they're sensitive to the operating frequency. I don't
think you can make major changes, such as going above
20kHz, and have them still work OK.

Not only that, they fade over time, some get spots, they are all
faint and in general give miserable "service" for the bother.
The lighting panel for flat screen monitors, etc on the other hand,
are very decent and have a simple, quiet driver.

 

[bitrex]

On 10/13/19 10:31 PM, Winfield Hill wrote:

bitrex wrote...

If the oscillation frequency and power output is mostly
determined by the characteristics of the transformer ...

In my experimenting with EL panels, years ago, I found
they're sensitive to the operating frequency. I don't
think you can make major changes, such as going above
20kHz, and have them still work OK.

Nope, seems unlikely. 800-2kHz is problematic though because it's around
the area where the human ear equal loudness curve bottoms out, even
small amounts of whine is easily heard in a quiet room and
objectionable. Do you know what causes the whine...magnetostriction in
the transformer?

Unfortunately the circuit I posted in the link seems relatively
insensitive on operating frequency with respect to component values
other than the transformer or supply voltage perhaps it was designed
that way. Only way I found to increase the brightness of the small EL
sheet it's driving is to increase the input voltage which also increases
the whine. Designed to be quiet with the properties of the original load
I guess, well doesn't help me much cuz the original part is long gone.

It would be nice to run several lengths on something like a 4192A LF
impedance analyzer to see what kind of load they present with respect to
frequency, unfortunately still don't have one of those. an impedance
analyzer/VNA is next on my to-buy list.

 

[bitrex]

On 10/14/19 1:37 AM, Robert Baer wrote:

Winfield Hill wrote:
bitrex wrote...

If the oscillation frequency and power output is mostly
determined by the characteristics of the transformer ...

  In my experimenting with EL panels, years ago, I found
  they're sensitive to the operating frequency.  I don't
  think you can make major changes, such as going above
  20kHz, and have them still work OK.


  Not only that, they fade over time, some get spots, they are all
faint and in general give miserable "service" for the bother.
  The lighting panel for flat screen monitors, etc on the other hand,
are very decent and have a simple, quiet driver.

It's too bad, when this type of tape is driven by a driver with more
oomph to it and higher frequency the glow it emits is very pleasing:

<https://imgur.com/a/DNIpujE>

It comes out a bit brighter and white-er in the pic than it really is.
If not for the fading and drive issues i'd prefer it for LCD
backlighting vs the white LEDs cheap LCD displays use for backlighting
now which I find really harsh and eye-strain inducing