SH1106 1.3'' display noise text

Other Hardware Displays
1

Hi, i have a pcb on which i have some endstops, arduino nano, servo pump and a 1.3'' display. If i power the circuit from arduino usb it works well, the display works well but if i power it from power supply(5v 3A) it displays the text but not full it gets erased. I tried with 100nf ceramic and electrolitic 100uf capactior direct soldered on vcc gnd, i use u8g2 library and tried with adafruit too. I used sh1106 before and worked well(the display was starting with GND) this one is starting with VCC, tried multiple displays.. and 2 power supplies. I have 4.7k on i2c
Video of problem: https://youtu.be/whEEq6hrilU

2

show us the schematic and the actual circuit

3

What does that mean?

4

I think he's saying the order of the pins on his current display are VDD GND SCK SDA (from the video)

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while there are similar displays with the order GND VCC SCL SDA like this one I happen to have handy

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I'm not sure whether that's a typo or the display he's using is a SPI display

5

A good ground.

Whatever is making the screen jump and scramble is making the sensor jump (between 10ml and 39ml)... probably bad ground.

6

Some displays pins are arranged GND VCC SCK(SCL) SDA, some are VCC GND SCK SDA... and some are "back to front" SDA SCK VCC GND or SDA SCK GND VCC

7

Why.
It could be unsafe to power sensors/displays from a different supply.
Strange things could happen when supplies have different voltages or one of them is off.
Phantom-powering is one of the dangers.

It should be no problem to power that display from the Nano. It draws very little current.
Leo..

8

My head went somewhere else entirely; I was trying to figure out if there was some weird power sequencing going on. Physical pin arrangements simply did come up on my mental radar. Come to that, why is that even significant? Ahh, it doesn't matter. It just utterly confused me, obviously!

9

Thanks everyone for replying, I'm sorry that I wasn't that clear with my explanation. The display is i2c and yes, I was referring of the pins order, the screen is displaying the value of the potentiometer in circuit and was jumping because in the video I rotated the pot to show the problem. I power the circuit from power supply because I have an mg996 servo and I didn't want to kill the Arduino.. plus that, the PCB is in a case in which you can't acces the usb c port. I could post the schematic but i didn't annotate it that good...

10

Which Nano (assuming classic Nano v3).
Try to power that display from the 3V3 pin of the Nano, which is a cleaner supply.
Remove the 4k7 resistors. The OLED display and Nano already has them built-in.
Assuming you have relatively short I2C wires (~25cm).
The Nano can be powered with 5volt on the 5volt pin, together with the servo.
Leo..

11

I thought of that.. but the i2c form A4 and A5 are 5v right? will it work supplied from 3v3 and i2c 5v? Chinese nano and the wires are >1cm on pcb and 20cm wires from PCB to display

12

Switched to 3.3v as Wawa said and it works perfectly. I didnt try this before because i thought i need a logic convertor. Thanks everyone!