3.3V Ebay LCD Modules

[rcbuck]

I am searching for 3.3V 1602 type LCD modules on Ebay. I find quite a few listed that have a description that says:

1* Blue LCD 1602 Blue screen with backlight display 1602A 5v module for arduino

Further down it says Voltage +3.3V DC
An example of this type listing is here:https://www.ebay.com/itm/Backlight-Screen-W-LCD-1602-2016-Display-For-Arduino-Blue-Module-1602A-3-3V-XG/283308112886?hash=item41f67abbf6:rk:1:pf:0

My question is if the module is made to run on 3.3 volts, why do they mention 5v for arduino?

There is a listing here: https://www.ebay.com/itm/3-3V-HD44780-1602-LCD-Display-Module-16x2-Character-LCM-Blue-Blacklight-NEW/272393846824?hash=item3f6bf04028:g:9~AAAOSw8w1X64YU:rk:9:pf:0
that doesn't mention 5v arduino. And he has sold 741 of the modules so I'm fairly sure they must work on 3.3V.

Does anyone have any experience with these 3.3 volt LCDs? If you have purchased a 3.3V one that does work by driving it directly from a 3.3V micro, could you post the link to what you purchased?

I have previously tried driving a 5V LCD with 3.3V data lines and it resulted in some of the characters being scrambled. When I inserted a level translator between the 3.3V micro and the 5V LCD, the characters were displayed properly.

Would I be better off to just put the level translator on my new board design and not take a chance on the "3.3V" LCD modules.

[ebastler]

Most likely a copy-and-paste error on the ebay seller's side. I assume some of these modules are made for a 3.3V supply, and other models for 5V.

It is not clear to me from your post which voltage (supply and logic levels) you actually intend to use. In either case, why don't you just buy a module from a vendor who states the voltage clearly and consistently?

The supply voltage needs to be a match in any case, of course. For the logic levels, driving 5V inputs with 3.3V output levels should work directly (since CMOS outputs should go close to 3.3V, and hence above the threshold for the 5V inputs). But you need to protect the 3.3V inputs from 5V output levels.

[fchk]

Most 5V displays also work with 3.3V, with two caveats:
1. Their internal clock is slower, so the whole timing gets slower
2. Contrast voltage (usually on pin 2) might be genative. You will need a 7660 in order to get a negative offset.

[rcbuck]

I am going to be using a PIC32 that runs at 3.3V to drive the LCD. I will purchase the module from the second link I posted. They do not say 5 volts anywhere on the listing.

Their internal clock is slower, so the whole timing gets slower

That may be why when I previously used a 3.3V processor to drive a 5V LCD some of the characters were garbled.

[amyk]

You need to examine the PCB and the datasheet for the controller to see if a voltage regulator is included/whether the controller will be fine with 5V.

It's more likely that 3.3V logic levels are not sufficient (especially the Vih(min)) when the controller IOVDD is powered by 5V.

[rcbuck]

I ordered the LCD module that says it needs 3.3V for power and for the LCD backlight.

Has anyone used a 3.3V LCD? If so, did it require a negative voltage for the VO pin? Or did they handle the VO voltage conversion on the module?

If I can get an answer to this question I can proceed with my PCB layout.

[mvs]

Has anyone used a 3.3V LCD? If so, did it require a negative voltage for the VO pin? Or did they handle the VO voltage conversion on the module?

3.3V LCD screen should have 7660 charge pump and caps on the board to generate negative supply. It is sole difference to 5V version.

PS both of your links are showing more common 5V version with unpopulated SO-8 footprint for 7660.

[fchk]

I ordered the LCD module that says it needs 3.3V for power and for the LCD backlight.

Has anyone used a 3.3V LCD? If so, did it require a negative voltage for the VO pin? Or did they handle the VO voltage conversion on the module?

You should ask for a complete datasheet from the display manufacturer and only buy a display after you have checked that the values in the data sheet match the requirements of your project. No datasheet - no purchase! It's just that simple.

This is an example of a 3.3V only display:
https://www.sparkfun.com/datasheets/LCD/ADM1602K-NSW-FBS-3.3v.pdf

[Bassman59]

I ordered the LCD module that says it needs 3.3V for power and for the LCD backlight.

Has anyone used a 3.3V LCD? If so, did it require a negative voltage for the VO pin? Or did they handle the VO voltage conversion on the module?

If I can get an answer to this question I can proceed with my PCB layout.

I've used the Newhaven NHD-0216HZ-FSW-FBW-33V3C with a 3.3 V supply and driving it from a 3.3 V micro without any other special considerations.

Basically, if the catalog or data sheet call out 3.3 V supply, then that's all you need.

[Wimberleytech]

I ordered the LCD module that says it needs 3.3V for power and for the LCD backlight.

Has anyone used a 3.3V LCD? If so, did it require a negative voltage for the VO pin? Or did they handle the VO voltage conversion on the module?

You should ask for a complete datasheet from the display manufacturer and only buy a display after you have checked that the values in the data sheet match the requirements of your project. No datasheet - no purchase! It's just that simple.

This is an example of a 3.3V only display:
https://www.sparkfun.com/datasheets/LCD/ADM1602K-NSW-FBS-3.3v.pdf

Interesting.  The 5V and 3.3V versions of this ADM1602 LCD both use the same controller that is rated from 2.7 to 5.5 Volts.  I wonder where the difference is. 

[floobydust]

The confusion is some LCD controller IC's are capable of running from 2.7-5.5V (i.e. ST7066), they are fine with 3.3V operation which is what the vendors are saying "3.3V/5V" but there are two builds of LCD modules.

For 3.3V power, the LCD board needs extra parts populated for -ve "N.V." voltage generator to have decent LCD contrast. This is the SOIC-8 and two capacitors on the PCB, that the 5V version leaves out. If your display does not have those parts, it is a 5V version.

I would design your board as if the LCD is a 3.3V part. If you get a 5V part you could add the three parts and change jumper J1 to make it 3.3V, and backlight resistor too.

pic and more info: https://mewpro.cc/2014/12/13/utilize-unused-footprints-on-5v-lcd-modules/
"Note: U3=MAX660, C1=C2=10uF, J1=J2=open, J3=close, R8=330 (R8 for back light current restriction at 3.3V)"

[rcbuck]

Floobydust, thanks for the information and links. If those parts are not on the modules when they come in, I will add them. Mouser stocks the chip.

You should ask for a complete datasheet from the display manufacturer

fchk, since I am buying these off Ebay, there is no telling who the manufacturer is. Most of the China Ebay sellers really have no idea of what they are selling. If you look at their webstores, the electronics stuff is mixed in with dresses, jewelry, perfume, and all sorts of other stuff.