Hi all,
I bought this 2.42" I2C OLED with SSD1309 controller:
after programming, I notice high frequency (audible) noise coming from the OLED/controller.
the sound is stronger the more content is presented (e.g. more pixels in "on" state) .
it's pretty annoying, and I really want to reduce, or remove this noise.
is there a solution?
thanks
Have you tried using decoupling capacitors on the power supply lines of the display?
the power is provided (along with data) by a wemos d1 mini: LOLIN D1 mini — WEMOS documentation
so I didn't try that, is it required? if so which capacitors should be used?
Yes. See my tutorial on the matter:-
Decoupling tutorial
The noise is coming from the inverter driving the display chip. You could also try some mechanical damping on the mount you have.
I see in your post that you recommend 47uF electrolyte and 0.1uF ceramic.
I currently have 47uF and 1uF, both electrolyte. is it good enough?
else I will have to fetch parts which would take some time 
about the noise source - well I don't have any mount yet.
the back doesn't look like there's much to generate noise that can be damped, I tried pressing various chips to see if it makes a difference, but it didn't.
where on the board do you suggest I apply damping?
No, it has to be ceramic, for reasons explained in that tutorial.
It also has to be applied as close to the display as possible with the leads as short as possible, especially on the leads of the ceramic capacitor. Excessive lead length adds to the inductance of the capacitor and so reduces the frequency where is stops acting as a capacitor.
On the mount. If it doesn't have a mount then suspended in mid air with stiff wires is as good as you can get. It is an attempt to stop any acoustic coupling.
The noise is coming from that inductor labeled L2.
thanks for the very quick replies and help.
alright I'll order some parts, and wait for implementation.
in a "circuit" that contains the wemos d1 mini, and the ssd1309+oled, that means across the GND and VDD ports you see in the picture, right?
I can try some hot glue around it, is it advised?
also, is the noise dual sourced? I mean, is the decoupling solution related to the inductor noise?
Correct.
I wouldn't do this, because it is too thick to flow round the windings of the coil. You could try some polyester varnish, that would be better at stopping the windings vibrating. However, it could probably effect the Q of the coil and might not function anymore, but that, I think, is a long shot.
While decoupling is always required for stable operation, then I am not sure if they are linked.
After the last post there are a number of old posts where people have had the same problem, have a read of these for other possible causes and solutions.
I actually don't see any windings. only the copper to terminal is visible.
it looks almost like this:
can you please share a link? if you mean the "related topics", I only see posts that deal with audio signal noise, and oled pixel noise, not audible noise from audio-less circuits
Simple, you can't. Have you tried applying pressure on that part to see if it reduces the noise?
As it is labeled L2, this suggests there might be an L1, but I don't see it on that side of the board.
However, you could just have a crappy board, despite the horrendous price Amazon charges you.
Yes I do, I have not read all of them.
I tried, it didn't.
schematics I find in aliexpress suggest that the SPI version has L1, and the I2C version has L2
I considered this. but since all of these 2.42" OLED I2C circuits look the same, I don't think it's smart to just buy the same model (it is somewhat expensive).
I prefer to try and solve the issue, or go for the inconvenient SPI version
Only on Amazon, they are the worst price you can get. Yes they are at great prices, but they are only great for them, not you.
I think I am out of ideas here now. These is a limit to what can be done on line.
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