Potentially dead LCD display, i need info about it

Other Hardware General Electronics
1

Hi there!

i am working on a sytem with a nano microcontroller, a 20x4 display (hd44780 based) and an OpAmp (TL072CP).

all this on a breadboard for now.

i first tested the display to be sure my code was doing the job. all clear, then i wanted to set the OpAmp, which output is hooked to nano Analog input.

first i powered in with 5V but realized that min voltage was 7V and max, 36v.

to power it, i decided to use a 12V 9,6/12W power supply i have (with a still charged capacitor :face_with_spiral_eyes: ... remember to always check that, it's dangerous !).

then something weird happened : when i powered the OpAmp, the LCD device immediately started to display "garbage-characters". Besides my computer, was doing repetitive "plug-unplug" sound, my mouse even stoppped working for a few seconds !

what on earth did happened??? is it due to the OpAmp Noise? (note that nothing from the OpAmp was directly connected to the display, it was on the same voltage rails, that's it)

i am not familiar with that kind of phenomenon (if there's any) regarding OpAmps.

please help!!! :cry:

because now, my display seems dead! i tried again and again to make it work, it powers up, no problems, it receives data, the Enable and RS pins are receiving signals, but it displays garbage. whatever program i use for it, it is still displaying garbage,

is it possible that HD44780 circuits are dead ? is there any way to fix the display?

i say it again: it was working properly before this incident.

PXL_20240803_103341543
PXL_20240803_1033415431920×1080 143 KB

in this example, it supposed to display "this is a test" lol

3

Hard to be sure, sounds like you plugged 12 volts somewhere it wasn't supposed to be.

I am sure you are sure you did not… and I'm sure I can't say for sure.

You may have damaged everything involved, so start switching things out.

Check the Nano alone with a simple sketch like blink. With nothing else connected.

You may need to reboot your computer, use a different cable and USB port, any or all three.

If the Nano works, add the LCD circuitry. Use the simplest test sketch you can.

And so forth.

a7

4

You may need to reboot your computer, use a different cable and USB port, any or all three.

my devices worked again without problems after.

sounds like you plugged 12 volts somewhere it wasn't supposed to be.

that's impossible, i checked the pinout. I am sure that the VCC and ground has been hooked up properly.

for real, everything happened when i powered on the OpAmp. like it created, i don't know some kind a EMP, that's why it looks crazy for me

it is possible that the circuit is malfunctioning.

5

You've done everything right and nothing wrong - Case Closed - another innocent project down the drain owing to the serendipitous "opamp emp".
Thanks for the advisory.

1 Like
6

So you obviously supplied 12V to the LCD.

7

Of course i didn't do that !

the 12V was isolated from the rest. the LCD display was indeed 5V powered.

8

No it's not "isolated from the rest" when you stop and think about it.
12V got somewhere it shouldn't have, your hardware is damaged. Need a new LCD display and the Nano would not be too happy either, it might have damaged pins. School is expensive.

opamp emp is not in the OP picture, wonder how it is connected, to what analog input.
If the op-amp output was over 5.7V then current flows backwards into the whole Arduino 5V rail and moves it up. That explains things as well as the USB fault, it tried to backflow into the PC.

9

This is probably what happened.

I had my +12V and Ground from the 12v supply, hooked on two lines on my breadboard.

i don't know where, but somewhere, something was connected to the LCD (or the nano) and this happened.

your scenario makes totally sense.

thank you !

i learn from that mistake

10

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