Varing Alphanumeric LCD contrast

[NewbeeAVR]

Hi I bought 16x4 (white on blue) LCD JHD brand from store. But it's contrast is set to high by default. Using potentiometer can not give any variation. What may be the problem?

 

[D.A.(Tony)Stewart]

Wrong bias voltage. but the correct voltage depends on LCD, datasheet, your circuit and supply measurements.

 

[NewbeeAVR]

In the following data sheet they have given 5v as the supply voltage. I am using 12v adapter and 7805 to get 5v.

**broken link removed**

 

[KlausST]

Hi,

This is not a complete datasheet....

But it says contrast voltage typ is 4.7V. How did you generate this 4.7V?
Did you verify the voltage with a DVM? If not, then do it.

Klaus

 

[Externet]

And observe the contrast adjustment from different angles or points of view.

 

[pjmelect]

Show your circuit, potentiometer wired wrong?

 

[D.A.(Tony)Stewart]

Use pot 10k to 0V = Vss