REQ: Looking for a circuit to power up LCD backlight

[Alienbeing]

I have a 4x20 LCD. Would like to know if someone has a circuit (schematic & parts list) to make a circuit that can power a electroluminescent strip that is placed behind the LCD. It is an inverter circuit that will use 5 VDC input. I had an inverter but it shorted out when I applied 5 vdc to it for some reason. It did work at one time.

Thanks,
Alienbeing

[awarapunshee]

Did your 5V source has enough current to supply the LCD?

Regards

[Alienbeing]

It had plenty of current but I think the inverter was made only for a 3vdc input. I don't have any specs on it because it was stripped out of a LCD meter that went bad. The inverter worked last time I tried it but now it overheats and won't produce the 90 volts on the output. It's a small surface mount device. I can't trace the part number on the device to any info on the web. So, I figured I'd just try and build a circuit to do the same thing. 

Alienbeing

[zorx]

I think that you shouldn't connect 5V directly to the backlihgt pin of LCD (because it is LED). Use 22 Ohm resistor (or similar). And read LCD datasheet to see current requirement for backlight.
You can control backlight (ON/OFF) if you insert switching transistor (e.g. 2N2222). Collector circuit consists of +5V, 22 Ohm resistor, A (Anode) pin of LCD, K (Cathode) pin of LCD, collector, and emitter connected to the ground. Control signal (e.g. pin from 8051 or PIC) goes to the transistor base via 1 kOhm.

   +5V
    ---
     |
     |
    /
    \
    /  R1 = 22 Ohm
    \
     |            ___________
     |       A  |                 |
      --------|    LCD        |
                 |                 |
      --------|__________|
     |       K
     |
     |
     |   Q1 = 2N2222 (NPN)
     |C 
      \    B     R2 = 1kOhm
       |---------/\/\/\-----------| ON/OFF command - TTL level
      / E
     |
     |
   ----  GND
    --
                 

[Trishool]

It had plenty of current but I think the inverter was made only for a 3vdc input. I don't have any specs on it because it was stripped out of a LCD meter that went bad. The inverter worked last time I tried it but now it overheats and won't produce the 90 volts on the output. It's a small surface mount device. I can't trace the part number on the device to any info on the web. So, I figured I'd just try and build a circuit to do the same thing. 

Alienbeing

Alienbeing is that an TFT device? you clearly bypassed the Absolute maximum ratings i guess you can buy LCD inverters from manufacturers like NEC http://www.eu.necel.com/_pdf/EN0493EJ1V1DS00.PDF  , I dont think it would be an good Idea to built an inverter as self made inverters would induse noise and flickering in the display and electronics.

Ts

[zorx]

No specific software. Just keyboard & fingers. Plain old ASCII 
But you can use software like ASCII Art Studio from

Code:

www.torchsoft.com

to convert pictures (GIF, JPG, PNG, ...) to ASCII file.

Already posted here. Look at:

Code:

http://www.sonsivri.com/forum/index.php?topic=5007.0

[Alienbeing]

I think that you shouldn't connect 5V directly to the backlihgt pin of LCD (because it is LED). Use 22 Ohm resistor (or similar). And read LCD datasheet to see current requirement for backlight.
You can control backlight (ON/OFF) if you insert switching transistor (e.g. 2N2222). Collector circuit consists of +5V, 22 Ohm resistor, A (Anode) pin of LCD, K (Cathode) pin of LCD, collector, and emitter connected to the ground. Control signal (e.g. pin from 8051 or PIC) goes to the transistor base via 1 kOhm.

   +5V
    ---
     |
     |
    /
    \
    /  R1 = 22 Ohm
    \
     |            ___________
     |       A  |                 |
      --------|    LCD        |
                 |                 |
      --------|__________|
     |       K
     |
     |
     |   Q1 = 2N2222 (NPN)
     |C 
      \    B     R2 = 1kOhm
       |---------/\/\/\-----------| ON/OFF command - TTL level
      / E
     |
     |
   ----  GND
    --
                 

It's not an LED that is providing the backlight, it is an electroluminescent strip that needs about 90 volts from an inverter circuit. I just think I applied to much voltage to the input pin of the inverter and fried it. Didn't have any specs on it. Couldn't find anything on the part number that was stamped on the inverter.

Trishool
Thanks, for the info (PDF) file.

Alienbeing

[ALPK]

hello if you serial coil(any) and with swiching 1.2 khz +5v ellamp lighting.

[Alienbeing]

This is what I found that will work perfectly for LCD backlighting.

Code:

http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=289&M=NDL-201

Alienbeing

[gianmagna]

hello Alienbeing

before I used this product chip HV832 for electroluminescent backlight.
 the product is obsolete, now use HV852 , SMD package
good reparation !
link www.supertex.com/pdf/datasheets/HV852.pdf

gianmagna

[Trishool]

Here is a schematic for LCD inverter if you want to make one but it would not be easy  . Next I am posting links for reparing hope this helps you.

http://www.ka1mda.org/ham/746/

http://www.fairchildsemi.com/ds/FA%2FFAN7311.pdf

http://www.ferroxcube.com/appl/info/framebarnew.pdf

Ts