Negative voltage for LCD driving?

[Fredrick]

I have a display and in the datasheet it says that it need "Negative voltage for LCD driving" on the VO pin?

What does that mean? can i connect it like it´s discribed in the PBP manual?

Datasheet
http://www.vtronic.com.cn/products/images/VT162B-B.pdf

[Melanie]

What happens if you do connect the Contrast pin as per the manual?

[Fredrick]

I don´t know, i have´t tryed yet.
Do you think it will work whitout a negative voltage?

[Melanie]

Well it's not going to harm it.

You worry about providing a negative voltage if it doesn't work through conventional ways first.

If you do need a negative voltage, then if you have a PIC that can give you HPWM, we can easily generate one from that with a few components.

[Samoele]

Hi,

3 pin on LCD is normally tied to GND. negative supply is need by extrem contrast or low temperatures.

You can help with PWM from PIC. see Attachment


Samo

[Dave]

Fredrick, You can also use the -9 volts from an RS-232 interface ic if you are using a serial interface to your computer for boot loading.. I do this quite often.

Dave Purola,
N8NTA

[Fredrick]

I use a USB interface with a FTDI RS232 chip on the board.

I will try first and just connect it to GND and se what´s happends.

[Fredrick]

Just connect the Vo to GND does´t work, all the "pixels" on the display are showing but no text.

I think this display needs negative voltage for LCD driving..

[Samoele]

You have problem in software. When show all pixels on display then is contrast ok. Check your data signal

[mackrackit]

Just connect the Vo to GND does´t work, all the "pixels" on the display are showing but no text.

I think this display needs negative voltage for LCD driving..

Try connecting as the manual shows with a pot as a voltage divider, then try adjusting until the display is clear.

[Fredrick]

The display i working now but it´s slow.

The problem was that i have forgot to connect the "Enable" signal, i checked the connections severel times before i notice that. I have must been tired

[mackrackit]

The display i working now but it´s slow.

The problem was that i have forgot to connect the "Enable" signal, i checked the connections severel times before i notice that. I have must been tired

Do not tell anyone, but I made a similar mistake awhile back.