Ok, I'll try it.
Thanks!

 

hi,
eng1 and I, consider the possibilty that without the backlight LED current limiting resistor, the +5V supply line could be getting pulled down, if held down long enough the +5V regulator could be going into thermal shutdown.

You said that you had the pixel blocks for a while then they faded away, this again suggests a possible power supply problem.

Do as eng1 suggests, disconnect the LCD backlight..

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

I got it, thanks!

 

why not power the back-lit from unregulated voltage and change the current limit resistor to a suitable value?

__________________
Regards,
Sarma.

 

hi Sarma,
We are trying to debug his project, the problem is that we are not sure if the LCD is faulty, the wiring wrong or the power supply/backlight is at fault.
The programs have been run OK in PIC's on my system OK.

We are suggesting removing the backlight as a possible cause of his problem, its not needed at this stage.
When the LCD works then he can put the backlight on...

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

I understand Eric,
Wish you all A Merry Christmas

__________________
Regards,
Sarma.

 

Many thanks... Wishing you a Prosperous New Year!....

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

I used JHD162A display earlier. I used a 10 ohm resistor and worked fine. this might help you in settling the resistor value. the pot used for contrast could be replaced with 10K and 1K2 (lower value towards Vss). this will not leave things to chance for the O P

__________________
Regards,
Sarma.

 

I'm upset now, the LCD still not displaying any character. I tried to connecth the backlight with resistor, nothing display at all. Then I changed output port, cannot work as well. I change the breadboard I used also not function. All the possiblity that may cause the LCD not working have been try.... What should I do now? change a new LCD?

Thanks!!

 

don't be upset for every failure. this is where you really learn, hardware or software- if everything works as you wire- there is no learning-- FINE--

check with ref to pin1 of LCD the DC voltage on pin3of the LCD.
it should be around 0.8 to 1.4 V Dc approximately.
if it is more , it will show all dark rectangles( each character is made up of 5*7 dots which forms a rectangle) under situations all the 35 dots will turn dark. like that all 16*2 characters turn dark rectangles.it should be adjusted around 1V+/- 0.25

then the display will come up.

then check up the connections for correctness and for dryjoints.
try to connect a 0.1uF capacitor across pins 1&2 of the LCD .
i have used it across various softwares and it works.

however please check whether any of the COBs(Chip On Board) on the back of display is WARM or HOT. this happens if you have pulled out the display while it is working.(NEVER DO IT IN FUTURE) If so, I feel it should not happen, the display has gone and you may have to replace. please give a feed back.

__________________
Regards,
Sarma.

 

Really thanks for your advise. I'll give you a feed back soon. Thanks...

 

Sorry for late reply since recently is quite busy for other assignment.

I've tested the LCD today. As your suggestion, I've connected a 0.1uF capacitor accross pins 1&2 of the LCD. The circuit have some improvement that the partial dark rectangles appear longer time than before. Erm...I'm not sure that I've use 2 capacitors to accross pins 1&2, which one capacitor connect to pin1 to ground, and another capacitor connect to pin2 to Vcc. Am I correct to connect by this way?

Beside, you had mentioned that the LCD will show all dark rectangles if the voltage is more than 0.8 to 1.4V. But my LCD is just turn on the dark rectangles partially, and appear a few second. What does it mean for my circuit? Is the programme problem or the hardware not stable?

Thanks!

 

hi,

>>I've tested the LCD today. As your suggestion, I've connected a 0.1uF capacitor accross pins 1&2 of the LCD. The circuit have some improvement that the partial dark rectangles appear longer time than before. Erm...I'm not sure that I've use 2 capacitors to accross pins 1&2, which one capacitor connect to pin1 to ground, and another capacitor connect to pin2 to Vcc. Am I correct to connect by this way?

Beside, you had mentioned that the LCD will show all dark rectangles if the voltage is more than 0.8 to 1.4V. But my LCD is just turn on the dark rectangles partially, and appear a few second. What does it mean for my circuit? Is the programme problem or the hardware not stable?

If you are trying to run the program I posted 'lcd2line1' that works OK in the PIC. It most likely you have a problem in your hardware.

I have found that different LCD's do have a different pixel block contrast level.

As I suugested, write a simple LED ON/OFF program and prove the hardware for the remainder of the project.. once you are sure the project works without the alpha-numeric LCD, then you get a idea where the problem lies.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

hi,

>>I've tested the LCD today. As your suggestion, I've connected a 0.1uF capacitor accross pins 1&2 of the LCD. The circuit have some improvement that the partial dark rectangles appear longer time than before. Erm...I'm not sure that I've use 2 capacitors to accross pins 1&2, which one capacitor connect to pin1 to ground, and another capacitor connect to pin2 to Vcc. Am I correct to connect by this way?

Beside, you had mentioned that the LCD will show all dark rectangles if the voltage is more than 0.8 to 1.4V. But my LCD is just turn on the dark rectangles partially, and appear a few second. What does it mean for my circuit? Is the programme problem or the hardware not stable?

If you are trying to run the program I posted 'lcd2line1', that works OK in the PIC.
Its most likely you have a problem in your hardware.

I have found that different LCD's do have a different pixel block contrast level.

As I suggested, write a simple LED ON/OFF program and prove the hardware for the remainder of the project.. once you are sure the project works without the alpha-numeric LCD, then you can get an idea if the LCD is faulty or not.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Sorry, I have forgotten to mention that I didn't use your programme today because it's quite confusing. Today I had tested the hardware with a simple LED ON/OFF programme. LED works, but LCD not. Also, I used LED to test my LCD programme that I've slow down the delay time, the result is just like what I had set. But LCD still doesn't work......