Newhaven Display Forum

Newhaven Products => Character LCDs => Topic started by: DaveG on February 17, 2015, 01:16:29 PM

Title: NHD-0212WH-ATMI-JT# on 3.3V
Post by: DaveG on February 17, 2015, 01:16:29 PM
Is it possible to run the NHD-0212WH-ATMI-JT# with Vdd = 3.3V if V0 is connected to a negative supply?  I know this can be done with other displays that use the ST7066, but it's not mentioned the datasheet for this display.
Title: Re: NHD-0212WH-ATMI-JT# on 3.3V
Post by: Paul_B on February 17, 2015, 05:05:34 PM
Hello,

To answer your question no, the optimal contrast needs to be around 0.8V. Please see page 5 in the displays data sheet for the electrical characteristics.   

http://www.newhavendisplay.com/specs/NHD-0212WH-ATMI-JT.pdf
Title: Re: NHD-0212WH-ATMI-JT# on 3.3V
Post by: DaveG on February 17, 2015, 05:43:09 PM
Hi Paul,

Not sure I made my question clear.  In the datasheet, page 5, "Supply for LCD(contrast)" is spec'd as "VDD-V0", 4.2 volts.  Yes, for a +5 VDD, optimal V0 would be +5 - 4.2 = .8 volts.  But, if VDD = +3.3 volts, V0 would be +3.3 - 4.2 = -1.1 volts.  The datasheet for the ST7066 says it will work with VDD = 3.3 volts and V0 negative.  Is there any reason this LCD won't work that way?
Title: Re: NHD-0212WH-ATMI-JT# on 3.3V
Post by: DaveG on June 10, 2015, 12:02:05 PM
Well, I tried it anyway, and it does work.  You can run this display on 3.3V.  V0 gives good contrast in the -0.6 to -1.2 volt range.  I generated the negative voltage with a simple charge pump circuit driven by the PWM output of the microcontroller.  Changing the PWM duty cycle allows for software adjustment of the contrast.
Title: Re: NHD-0212WH-ATMI-JT# on 3.3V
Post by: Paul_B on June 10, 2015, 02:00:01 PM
Hi Dave,

Glad to hear, thank you for posting an update  :)