16X2 LCD contrast voltage(Vo) is not stable

[amit.kumar11]

Dear All,

I am using a 16x2 LCD. I have around 15 no LCD modules. 3 LCDs are working fine but with some of the LCD i am facing issue with contrast pin. If I switch on the board, everything is coming fine but after some time display is going to full brightness mode. I checked the Vo pin voltage its going to 4.5V. Initially its around 0.8V which is opk for contrast pin.

I am not able to understand, why suddenly Vo voltage starts varying.

Also If i disconnect LCD module from my board, then voltage at Vo pin in my board is stable.

Any help will be appreciated.

LCD part number-NHD-0216K1Z-FL-YBW


Amit

 

[esp1]

hi,
How is pin#3, Vo, connected within your circuit.?
E

 

[KlausST]

Hi,

Usually the contrast voltage must be supplied by the user, not by the display.
So if it is not in the expected range you should pull it to the expected level.

This may fail if there is a high current in/out of the VC pin. Check datasheet to finde max. current and then check circuit on this.

Klaus

 

[amit.kumar11]

Vo is connected using a pot of 10K.