Lcd Not Working..

[koossa]

Good day

I'm using a 16F877 with 16x2 Character LCD on a breadboard.

I have search everywhere for a LCD that uses low current and specific dimensions.
I have found one, but could not get it to work.

The old LCD is working perfectly. I have just replaced my old LCD with the new one and connected Vo to ground just to see if it is giving me the black boxes, but no luck.



Thank you
Koos du Preez

[DynamoBen]

Black boxes are good that means the new lcd works.

You will want to make sure the lcds are pin compatible. I have had cases where one model lcd had one pinout and the other had something completely different. Compare the datasheets.

Also, try increasing the LCD_COMMANDUS and LCD_DATAUS the new lcd may be a bit slower to respond.

[koossa]

Thank you for the reply, I will try the suggestions.
I Know black boxes are good, but I do not get them?

[koossa]

This one is supposed to work?
Controller/Driver: KS0070B

[DynamoBen]

If the LCD is wired improperly it can permantly damage the lcd. (hence no boxes)

[koossa]

I have done the following

DEFINE LCD_COMMANDUS 4000
define LCD_DATAUS 555

As well as replaced the LCD with a new one, but still nothing?

[DynamoBen]

You will need to find out what makes the two units different. Compare datasheets. This difference could be the problem.

[Ingvar]

As far as i know, KS0070B and HD44780 are compatible. You need to check the pinning of the displays, they may be different. You also need to make sure that the display is ready to recieve data before you use LCDOUT, some displays are really slow. Give it a couple of seconds.

/Ingvar

[koossa]

I have bought myself a 100k potentiometer and connect it to the LCD's Vo Pin, but does not get any response from the display?

A strange thing, I don't know if this is supposed to do it, I'm a bit new in electronics.

On the LCD's VDD Pin I get 5v when I remove the LCD, but when the LCD is connected I only get +-1.2volt, is this normal?

[Dwayne]

That is a high voltage drop....
ARe you SURE your LCD is a low current LCD??? There are LCD's out there that take 300 mils to run! I happen to have 2 of them...And they will blow a unsinked 7805 in a extremely short time... and will blow a 7805L in a even quicker time.

How about your LCD's display contrast? is it adjusted correctly? usually a 10K pot with center going to your contrast pin and ends going to +- is all that is needed....Adjust pot until black squares show up. Some LCD's do not need this pot...Some do.

Dwayne

[koossa]

I Have uploaded the datasheet.
As far as my knowledge go it looks like max Module Supply Current 2.0 mA.

I have connected a pot, but nothing happened when I turn it from one side to the other.
Have tried a 10k and 100k pot, but no one is working?

[NavMicroSystems]

...On the LCD's VDD Pin I get 5v when I remove the LCD, but when the LCD is connected I only get +-1.2volt, is this normal?

I guess your LCD is DEAD

[koossa]

Hi Ralf

I have replaced it with another one, but it does the same thing.
Do you think both of them could be dead?

If I connect my Pot's left pin to +5v and right pin to GND and Vo to middle pin and measure the voltage over my 7805's input voltage and gound it measure 4.3 volts and if I remove the pot it give me 8.03 volts.

[NavMicroSystems]

...If I connect my Pot's left pin to +5v and right pin to GND and Vo to middle pin and measure the voltage over my 7805's input voltage and gound it measure 4.3 volts and if I remove the pot it give me 8.03 volts.

Well, in this case you should check your power supply.
If the Input of the 7805 really drops that much with a resistive load of several k there is something wrong with your PSU.

[Dwayne]

Hello Kossa,

k>>I have replaced it with another one, but it does the same thing.
Do you think both of them could be dead?<<

I think you have a voltage problem, as well as a possible current problem.
Put a 100 ohm resister on your output leg of your 7805, and make sure it stays at 5 volts (or very close). (This will help verify your 7805 is somewhat good). Put a cap (1000uf) on the output leg to ground, to make sure you do not have any "ripples" that will interfere with your PIC chip...Check the output with the resistor... should be very close to 5 volts.

If the above works, then disconnect your LCD +5, and connect everything but your LCD to the 5 volt source (you can remove the 100 ohm resistor).. Make sure the voltage is close to 5 volts....If not.. your problem is in the PIC circuitry....If it is close to 5 volts you are ok still....

Now connect the LCD by plugging in the 5V on the LCD the Voltage should STILL be 5 volts, or very close. If it is, then you have a chance of being ok. If not, you may have a bad LCD or something of a sourt.

Kossa >>If I connect my Pot's left pin to +5v and right pin to GND and Vo to middle pin and measure the voltage over my 7805's input voltage and gound it measure 4.3 volts and if I remove the pot it give me 8.03 volts.<<

8.3 volts?? what happened to 5 volts? Check your voltage source. Your whole circuit should be no more than 5 volts. You are saying 8 volts? Are you saying your input voltage to your 7805 is 8 volts??? If this is so, fine... but connect your pot to the 5 volt source (your 7805 output pin) and ground... not the 8 volt source(input to the 7805) and ground.

Dwayne

[koossa]

Hi Dwayne

Thank you very much I will try everything you've said.

PS:I have not connected my pot to the 8v, but to the 5v output side.

[Ingvar]

Did you check the pinning? As far as i can see it uses a different pinning than normal. Also the fact that your powersupply drops imply that there is a wrong connection somewhere.

[koossa]

Hi Ingvar

Thank you I will double check it and see if I could find the problem.

The only difference that I can see is Pin 1 on the HD44780 is now pin 14 and every pin just shifts up.