LCD Backlight problem

Started by Anushka Parab December 29, 2006
Dear yahoogroup,

Kindly Help to solve the backlight issue

My project is in very critical stage because backlight of the LCD not
working

We have the Winstar LCD Module WX320240C0 with EL BackLight.

With inverter WIEL2#

Practically the Inverter characteristic

Inverter (Without any load connected to Fluke 196B scope meter)

I/P --> 5V

O/P --> 179VAC / 6.56KHz

Lcd is working fine without backlight

But when I lit the backlight all the content of the LCD disappers

Back light specification give in the datasheet of LCD is as follows

Inverter Characteristic given in the datasheet

Backlight connection given to the LCD module in the datasheet is as follows

Kindly suggest any solution to lit the backlight of the LCD

Is there any problem of inverter?

Is required any series or parallel Load in between the LCD & the Inverter ?

Is there any current problem?

Kindly guide us to solve the backlight problem

Thanks & Regards,

Anushka Parab

Executive

ED-ELECTRONICS Dept.

MIDCO LIMITED,

Metro Estate,

Vidyanagari Marg,

Kalina,

Mumbai-400098

Office Ph: 91-022-6771133

Office Fax: 91-022-67711444

Mobile:9867486560
> -----Original Message-----
> From: m...
> [mailto:m...] On Behalf Of Anushka Parab
> Sent: Friday, December 29, 2006 5:28 AM
> To: m...
> Subject: [m68HC11] LCD Backlight problem
> We have the Winstar LCD Module WX320240C0 with EL BackLight.
>
> With inverter WIEL2#
>

>
> Lcd is working fine without backlight
>
> But when I lit the backlight all the content of the LCD disappers
>

>
> Kindly suggest any solution to lit the backlight of the LCD
>
> Is there any problem of inverter?
>
> Is required any series or parallel Load in between the LCD &
> the Inverter ?
>
> Is there any current problem?
>

If the backlight works ok, it may not be a problem with the inverter itself.
No extra loads should be necessary if the backlight is connected to the
inverter output all the time. You should switch the backlight on/off by
switching the inverter input on/off (not disconnecting the lcd backlight
from the inverter).

Maybe one of the following can explain the problem:

1. The current drawn from the inverter (60 mA) is too much for the power
supply to handle, the supply voltage may drop so that the microprocessor och
lcd unit stops working.

Check by measuring the 5V and also by temporary using a larger power supply
and see if the problem remains.
2. The power supply may be able to supply the power but the inverter may
cause a current surge at startup, if so a larger decoupling capacitor over
the power supply output may correct the problem.
3. Some contrast issue with the display?

Check by switching the backlight on and then off while keeping the other
system on all the time. Does the display look normal again after the
backlight is switched off? If so check the display manual for contrast
setting.
4. The high AC voltage in the two conductors from the inverter outputs may
disturb other circuitry, move them away from other boards and check if that
makes any difference.

Anders
Thank you for your reply,

Actually Backlight of LCD is not working .

We have the inveter

Which has practical characteristic

Inverter (Without any load connected to Fluke 196B scope meter)

I/P --> 5V

O/P --> 179VAC / 6.56KHz

Also attaching the datasheet of the lcd & inverter.

Happy NEW Year ! 2007

Anushka Parab

Executive

ED-ELECTRONICS Dept.

MIDCO LIMITED,

Metro Estate,

Vidyanagari Marg,

Kalina,

Mumbai-400098

Office Ph: 91-022-6771133

Office Fax: 91-022-67711444

Mobile:9867486560

_____

From: m... [mailto:m...] On Behalf Of
Anders Friberg
Sent: Friday, December 29, 2006 5:01 PM
To: m...
Subject: RE: [m68HC11] LCD Backlight problem

> -----Original Message-----
> From: m68HC11@yahoogroups .com
> [mailto:m68HC11@yahoogroups .com] On
Behalf Of Anushka Parab
> Sent: Friday, December 29, 2006 5:28 AM
> To: m68HC11@yahoogroups .com
> Subject: [m68HC11] LCD Backlight problem
> We have the Winstar LCD Module WX320240C0 with EL BackLight.
>
> With inverter WIEL2#
>

>
> Lcd is working fine without backlight
>
> But when I lit the backlight all the content of the LCD disappers
>

>
> Kindly suggest any solution to lit the backlight of the LCD
>
> Is there any problem of inverter?
>
> Is required any series or parallel Load in between the LCD &
> the Inverter ?
>
> Is there any current problem?
>

If the backlight works ok, it may not be a problem with the inverter itself.
No extra loads should be necessary if the backlight is connected to the
inverter output all the time. You should switch the backlight on/off by
switching the inverter input on/off (not disconnecting the lcd backlight
from the inverter).

Maybe one of the following can explain the problem:

1. The current drawn from the inverter (60 mA) is too much for the power
supply to handle, the supply voltage may drop so that the microprocessor och
lcd unit stops working.

Check by measuring the 5V and also by temporary using a larger power supply
and see if the problem remains.

2. The power supply may be able to supply the power but the inverter may
cause a current surge at startup, if so a larger decoupling capacitor over
the power supply output may correct the problem.

3. Some contrast issue with the display?

Check by switching the backlight on and then off while keeping the other
system on all the time. Does the display look normal again after the
backlight is switched off? If so check the display manual for contrast
setting.

4. The high AC voltage in the two conductors from the inverter outputs may
disturb other circuitry, move them away from other boards and check if that
makes any difference.

Anders
> -----Original Message-----
> From: m...
> [mailto:m...] On Behalf Of Anushka Parab
> Sent: Friday, December 29, 2006 2:28 PM
> To: m...
> Subject: RE: [m68HC11] LCD Backlight problem
>
> Thank you for your reply,
>
> Actually Backlight of LCD is not working .
>
>
>

You could follow this procedure:

A: Confirm that the inverter and lcd backlight is connected according to the
manual (note plus/minus inverter input I/G). Two separate conductors should
normally go from inverter output G and O to two separate backlight terminals
on the lcd unit.

B: Connect inverter I (5V) and G (0V) to a separate good 5V power supply to
check backlighting. Use multimeter to check DC and AC voltages on inverter
pins BUT beware of unpleasant and maybe lethal high AC voltage between O and
G (if not sure please consult qualified electrician for this).

C: If no light, replace with another inverter and lcd unit. If still no
light repeat A:, B: and C:, maybe use a separate lcd unit and inverter not
connected to the original system.

If light, continue by checking as described in 1-4 in last mail.

Anders