HD44780

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Guys I ordered a few LC displays.  I normal connect the LCD Display Bias to either the VCC or GND, can't quite remember which one.  My question is, which one?

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Last Edited: Sat. Feb 22, 2020 - 08:24 PM
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???

 

Whether the bias is connected to Vcc, Ground, a Pot from Vcc to Ground, or to a internally or externally generated negative voltage, all depend upon the LCD's support circuitry.

 

You will have to look at the manual for the actual, specific, LCD you purchased.

 

JC

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Feck it!  Bought some 10K pots.

 

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To soft control contrast consider driving bias with PWM ;-)

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From experience, the bias is closer to gnd. You only had two options - why didn't you try both? 

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Some of them do take a negative voltage on the contrast pin...but luckily I haven't seen one of those in 20 years.  

Best, always to read the data sheet for the actual display.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Try putting a common signal silicon diode like the 1n4148 on the contrast pin.  Put the anode on the contrast pin and the cathode to ground.  This forces the contrast pin to be at 0.7VDC, which is often the optimum setting for a potentiometer on this pin.

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Simonetta wrote:

Try putting a common signal silicon diode like the 1n4148 on the contrast pin.  Put the anode on the contrast pin and the cathode to ground.  This forces the contrast pin to be at 0.7VDC, which is often the optimum setting for a potentiometer on this pin.

 

nice one.