Help identifying pinouts for 16x2 LCD

[Vizier87]

Hi guys, it's been quite a while!

I've salvaged two 16x2 LCD parts, with the label BMX-01 and E226252 on the back, but they don't return any proper searches. However, I do believe the structure is pretty generic like other 16x2 LCD displays, so I just want to confirm whether the pinouts are correct as shown in the attached figures:

View attachment 67082

View attachment 67083

So I *think* the designated pins are (starting from the left, as shown by the first figure, top view):
1: GND
2: 5V
3: Vee (Contrast)
4: RS (Register Select)
5: R/W (Read/Write)
6: EN
7-14: DB0-DB7
15: LED+
16: LED-

However, the functionality test (to show all black boxes) wasn't successful so I'm rethinking my pin assignment. *If* going by the usual structure, are the pinouts correct?

Thanks everyone.
Vizier87

 

[Sceadwian]

That's clearly a Hitachi based display, make sure whatever you doing to initialize the display is being done properly. It's either a failure in the code/hardware that initializes the module or the module itself is toast.

 

[Mr RB]

16 pin 16x2 text LCDs always have the same pinout for the 14 main pins, but in some rare cases have the 2 LED pins at the wrong end. You can trace those LED pins with a ohmmeter to the LED and its resistor(s).

ALso you won't always get the "top row black boxes" until it is powered up with 5v AND the contrast voltage Vee is adjusted.

I have a "LCD tester" which is basically a black box with a PIC inside, a contrast pot and a 16pin header. It just flashes through the ascii chars, and also full black and full white boxes to test for dead pixels. Very handy!

 

[upand_at_them]

I've noticed from recent purchase that some manufacturers flip 15 and 16. Also, if your contrast isn't set right you'll likely see nothing.

 

[Ian Rogers]

The ground pin (pin1) doesn't look very well connected.... the solder pad is missing!

 

[dr pepper]

I've had some lcd's where the adressing appears to be different than standard, the top line isnt contiguous.

 

[Sceadwian]

Shouldn't prevent basic intialization and testing though dr pepper.

 

[Mr RB]

Yeah some old 16x1 LEDs are addressed as two lines of 8 chars. But all the 16x2 LCDs I have seen use two lines of 16 char addressing.

 

[Vizier87]

all right guys... thanks for the responses. I salvaged these from security keypads and by mistake, I pried opened the black metal casing of the LCD display, so it loosened the thing which affected the display.

However, after setting the pressure of the metal casing right back and resoldering it on the original board, it actually still works. I'll just have to program the thing and see where I'll go.

MrRB: I read the manual from EPE, and they said that connecting Vee to GND suffices for functionality testing, no? Also, I used 160k pot to set the Vee, that should be fine, shouldn't it?

upand_at_them: Yeah that's right, I noticed that the backlighting flips.
Ian rogers: Yeah, part of it broke off, leaving a small part connected but it's still working though.

Thanks guys!
Vizier87

 

[Vizier87]

Latest update:

**broken link removed**
Alright it works! Cool stuff going down here.
Thanks for the responses.

 

[upand_at_them]

Says "Invalid attachment".

 

[Vizier87]

Is it so? Here's the direct link:
**broken link removed**

 

[Sceadwian]

However, after setting the pressure of the metal casing right back and resoldering it on the original board, it actually still works. I'll just have to program the thing and see where I'll go.

Doesn't surprise me, virtually all LCD displays are pressure mounted to silicon risers that have conductive pads that attach to the actual glass. I'm slightly surprised it still worked though you said it was just lose, those things once they come truly lose are impossible to line back up again.

 

[upand_at_them]

Again, "invalid attachment".

 

[Vizier87]

Err... anyway it's just displaying the black squares on the upper row.

 

[Mr RB]

...
MrRB: I read the manual from EPE, and they said that connecting Vee to GND suffices for functionality testing, no? Also, I used 160k pot to set the Vee, that should be fine, shouldn't it?
...

Some brands work ok with Vee at 0v although not always with the best visibility. Other brands definitely need an adjusted Vee to be visible at all.

I have never used a pot as high as 160k, generally a pot between 5k to 50k is normal.

 

[dr pepper]

Scead, I've had a couple apart, the liquorice allsort piece of rubber that connects the board to the glass is as you know a stack of insulators and conductive rubber, I noticed that the pitch of the conductors is greater than the pitch of the connections on the glass, so that 4 or 5 bits of conductive material connect to each 'pad' on the glass, meaning exact alignment isnt necessary, and if a couple of the conductors dont connect the display still works.

I have a 2x16 where the characters light up red, the rest of the screen dark, if you connect contrast to ground you cant see any characters, and the contrast control itself is sensitive when used with a pot.

 

[Sceadwian]

Ahhh, thanks for the notice dr pepper, I see how that's so simple, I never took that close a look at them before, makes perfect sense now.

 

[Vizier87]

Anyway here it is:

View attachment 67171

Doesn't surprise me, virtually all LCD displays are pressure mounted to silicon risers that have conductive pads that attach to the actual glass. I'm slightly surprised it still worked though you said it was just lose, those things once they come truly lose are impossible to line back up again.

Yeah, so I was told. After opening it, a kid touched the rubber with his grimy hands, and said that thing's useless now. (so why did you touch it, idiot? ) But it still worked! Yippeee.

I have never used a pot as high as 160k, generally a pot between 5k to 50k is normal.

Confirmed, it still works. Just a cheap pot, mind you.