ryans I just received one of these (Essential Phone) today, and found pwm at all levels using the photodiode and oscilloscope, on the original firmware. (thanks to the circuit and post from @Wootever https://ledstrain.org/d/312-homemade-oscilloscope-to-detect-pwm-diy-guide/19 )
Updated to 8.1.0, then 9.0 and looks like the PWM still there. Its a weird looking waveform guessing around 180Hz, with 5-10kHz modulation within it. Adjusting the brightness just changes the gross amplitude)

I am presently using an LG v30+ which appears to be one of the few modulated screens that does not give me headaches, however I need to keep it above 42% brightness. I am not sure why, but the waveform on the scope 42-100% looks very different 0-41% so maybe something is in there to explain.
My previous phone was an LG G5 which did not show any pwm above 37% brightness.

Just a heads up though, I haven't used an oscilloscope/done engineering stuff in a long time, so this could all be something entirely different.
I don't know why the embedded image of the oscilloscope doesn't show - its at (remove spaces) https://imgur.com/ a/08FyTDR

https://imgur.com/a/08FyTDR

      12 days later

      Thanks for sharing. My old Galaxy S5 is not running well. I am afraid I might have to suck it up and buy a phone I know will give me headaches/strain in hopes that my eyes will adjust.

      • KM replied to this.

        Jimmyww I’m using a Samsung galaxy S3 with android 4.3 which I know is LED backlit but I’m fine with it (which is weird), however as a test I took the phone apart and put my screen on a S3 with android 4.4.4 I could feel straight away that it was giving me a headache. This makes me think that something changed in the software.

        The Galaxy S3 seems to have an AMOLED display which flickers at 240 Hz PWM frequency. Because you can look at it that probably means you do not have a problem with AMOLED and that 240 Hz flicker in particular.
        Eye strain that one may have after upgrading any OS has been confirmed by many people now. Unlike PWM, the reasons for this are still unknown and are astonishingly hard to capture.

        On the other hand, this means people could turn a device they previously thought to be totally unusable into a usable device by choosing the right ROM/OS.
        There are at least two factors at play: The display hardware and the software driving it. Making it tricky to find a working combination.

        Jimmyww I think the resolution of the screens plays apart too, with HD and UHD having very fine detail and vivid colours, which certain people are sensitive to??

        If you find a high resolution display that you can use, you can eliminate that theory. After all, the 720x1280 4.8" display you can use has ~306 PPI, so is pretty high-res already.

        It would be interesting to know if you can use a current custom ROM like LineageOS on a Galaxy S3. May help a little to extend its life (providing the unlocking procedure succeeds). Or it may introduce eye strain...

              KM Eye strain that one may have after upgrading any OS has been confirmed by many people now.

              I confirm that with Android. Factory-reset helped.

              • KM likes this.

                olgomar What does the LG's wave look like before and after the threshold? The more data we have, the better.

                I have been interested in buying a Rigol oscilloscope, but I am unsure if the display flickers or is otherwise uncomfortable. Could you measure the display if you have the time? It seems no one has ever done this before. They seem to use a very special form of LCD that differs from standard ones.

                Since you use the OPT101 circuit, did you find it can capture even high frequencies? I was concerned of its low bandwidth specs that say like "14 kHz".

                    ryans Before throwing the phone away, you might want to try to unlock it and install a custom ROM. Those may make the device more responsible. By doing do you could also provide info about which ROMs are eye-friendly on the S5.

                      KM Could you measure the display if you have the time? It seems no one has ever done this before. They seem to use a very special form of LCD that differs from standard ones.

                      Since you use the OPT101 circuit, did you find it can capture even high frequencies? I was concerned of its low bandwidth specs that say like "14 kHz".
                      Edit: I just re-read your post and saw you want a measurement of the Rigol, it is packed away again atm, so I will get on to that the next time I do some testing.
                      KM What does the LG's wave look like before and after the threshold? The more data we have, the better.
                      I have put up the LG G5 flicker measurement photos here:
                      https://imgur.com/a/McR5oFm
                      I do not know about higher frequencies with the OPT101 other than the tests I have done so far.

                            olgomar I meant the LG v30, because you said while it flickers it has a different waveform that causes you no trouble. Would be interesting to analyze the difference. It might help understand the difference between "good" and "bad" flicker.

                            If you are interested in your OPT101 speed, you could test it for example with this Raspberry Pi LED circuit: https://ledstrain.org/d/375-howto-create-pwm-led-flicker-with-a-raspberry-pi/3

                                KM I meant the LG v30, because you said while it flickers it has a different waveform that causes you no trouble. Would be interesting to analyze the difference. It might help understand the difference between "good" and "bad" flicker.

                                Sure:
                                https://imgur.com/a/7gvXEvj

                                    olgomar That is very interesting. The oscilloscope values are hard to see though. Was the input AC-coupled? Peak-to-peak voltage and frequency of the large spikes (50% brightness) the same as in the sine-like wave (38%)?
                                    By the looks of it I would guess that at 50% the hardware switches from 240 Hz to 60 Hz like my OnePlus 3 does it at ~25%.
                                    Like you I can not tolerate the 240 Hz but only the small 60 Hz pulsation.

                                    But is it small on your device? The peak-to-peak and maximum voltages, which are hard to see in the photos are most interesting.

                                        KM Was the input AC-coupled?

                                        The input was DC coupled

                                          KM I have been interested in buying a Rigol oscilloscope, but I am unsure if the display flickers or is otherwise uncomfortable. Could you measure the display if you have the time? It seems no one has ever done this before. They seem to use a very special form of LCD that differs from standard ones.

                                          Here is the experiment result of the Rigol measuring itself. It looks like a higher frequency than the OPT101 will allow so not sure what to make of it.
                                          https://imgur.com/a/eEXtcaF

                                          • KM likes this.

                                            KM The peak-to-peak and maximum voltages, which are hard to see in the photos are most interesting.

                                            The cursor measurements have been added on these ones.
                                            https://imgur.com/a/LdNgP3t

                                              Does anyone know what is going on when the phone is rebooted and a green screen with two gears shows up saying "Android is starting...Optimizing App 1 of 1"??? I am freaking out.
                                              I have never seen this before. I checked and automatic updates are deactivated.
                                              Have they found another way through? I really do not want more surprises...

                                              • KM replied to this.

                                                AGI I believe the Google Play Store updates itself automatically.

                                                • AGI replied to this.

                                                    Pixel 3 is due in about 1 month. I'm hopeful that we will find it usable!

                                                    • JTL replied to this.

                                                      ryans I wouldn't hold my breath. Not until OLED PWM is "solved".

                                                          KM Thanks. It actually happens every time I shut the phone down. Like, if I switch off twice in a row, it runs that optimization again...it cannot be a real update...Looks like some kinda bug...

                                                          • JTL replied to this.

                                                              AGI I think what it's doing is recaching all the app files. Not an update.

                                                              • AGI replied to this.

                                                                  JTL I know, I'm trying to be optimistic. I wonder if it's possible to have some kind of therapy to make people less sensitive to PWM. I'm concerned because I don't believe OLED is going away anytime soon. For people that aren't us, OLED is great, it produces some really nice colors.

                                                                  • JTL replied to this.
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