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Fredrick
- 9th January 2009, 22:22
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 itīs discribed in the PBP manual?

Datasheet
http://www.vtronic.com.cn/products/images/VT162B-B.pdf
Melanie
- 9th January 2009, 22:54
What happens if you do connect the Contrast pin as per the manual?
Fredrick
- 9th January 2009, 23:35
I donīt know, i haveīt tryed yet.
Do you think it will work whitout a negative voltage?
Melanie
- 10th January 2009, 08:59
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
- 10th January 2009, 10:20
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
- 12th January 2009, 11:37
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
- 12th January 2009, 13:36
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 whatīs happends.
Fredrick
- 14th January 2009, 19:35
Just connect the Vo to GND doesīt work, all the "pixels" on the display are showing but no text.

I think this display needs negative voltage for LCD driving.. :(
Samoele
- 15th January 2009, 08:03
You have problem in software. When show all pixels on display then is contrast ok. Check your data signal
mackrackit
- 15th January 2009, 08:22
Just connect the Vo to GND doesīt 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
- 15th January 2009, 10:33
The display i working now but itīs 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 :o
mackrackit
- 15th January 2009, 11:51
The display i working now but itīs 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 :o

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