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Display brightness of my old iMac
- Thread starter zoran
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EDIT (1/18/25) - Removed the attachment since the logic controller did not work to restore the sleep functionality. Shifting to a new approach using a MOSFET driver for the sleep functionality. See my later posts in this thread for details.
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@csdesign3
Comments about your option 1: I had read the same post by Frederic several times. He is clearly much more skilled and knowledgeable about Arduino boards and their programming language than I am. He is essentially using the Arduino board and his code to perform the same functions for which I am using the logic level converter and the PWM signal generator boards to do.
Although I can't confirm this, it looks like Frederic's method requires using the LCD driver board on screen display menu to adjust the display brightness. This requires many button pushes on the controller board to navigate the menu to the brightness setting. With my option #2 the brightness adjustment buttons are always directly available to you and require no navigation of on screen display menus.
Bottom line, if you are skilled with Arduinos and programming language and don't mind navigating the OSD menu to adjust brightness, Frederic's solution is a good option. If you don't like navigating an OSD menu and are comfortable soldering 4 wires to the PWM board and installing a couple of pushbuttons on the iMac, then option 2 from my post is probably the better method.
Comments about your option 2: I had also read this post. It was originally designed to be used to restore brightness control for iMacs with upgraded GPUs that didn't support native brightness control after the upgrade (most NVIDIA cards...). In the end, this is similar to Frederic's solution in that it is using different programmable PCB (the ESP 32) to provide the PWM signal and to act as an interface to MacOS.
What isn't clear is how this would work with a display that isn't your main display (it was designed to be used with the installed display). It may require you to go into the MacOS settings menu and adjust the brightness from within the Display app. Or, it is also possible that the keyboard brightness keys will control the brightness of all modified displays simultaneously (i.e., you dim or brighten multiple displays at the same time). Lots of unknowns.
Bottom line, I still prefer the certainty and simplicity of the buttons of my option 2 against the solution using the ESP32 board.
Regardless of my opinion, the best path is the one you are most comfortable with as both of these options as well as mine should ultimately result in "normal" brightness control which modifies the PWM duty cycle instead of modifying the video signal like the software brightness control solutions.
Even the software brightness control options aren't that bad. I just don't like the effect those have on other display viewability considerations such as colors - PWM duty cycle manipulation has no negative effect on these.
I'm more inclined to use your solution PWM signal generator and a step down module, actually i already waiting to recieve both to implment your solution and add 2 extra buttons to the monitor just to control brightness. I'm far from a programmer, but i'm very handy with soldering tools and hot air stations.. Still very interested using arduino to control via OSD the brightness and volume (but for another time), i want to fully use my imac monitor (internally it as 7 port usb hub, isght camera, sd card, dvd drive all working)..
Thank you again with your precious help and guidance.
Maybe this is not the right thread.. but figuring out how to use a better inverter board than the standard supplied one seems to be the way to go when converting an TB Display..
The TB Display does not have a separate Inverter board as the iMac, why it's difficult to follow the guide by SubDriver.
@SubDriver; To summarize in a few simple words; what is the main issue/challenge with the supplied inverter board for the 2k display that leads to the brightness issue? Did it feel like an easier option to figure out how to use the iMac inverter vs. fixing/improving the Chinese one?
Thanks
The issue (iMac 2011 27") is related with output voltage and the frequency, ENA(BLO) needs 3,3v and ADJ(PWM) 3,3v @13,3 Khz, these chinese boards for some reason supply more voltage at incorrect frequency witch leads to lower brightness (maybe to prevent some heat issue in long run). The are 1 or 2 users that transform 2010 imac's witch reports to direct use of controller board connected to apple inverter with success (no absolute confirmation here).
A better way of doing the correct thing is to analyze the Chinese inverter board and modify it, but there are many revisions of these Chinese controller boards/inverters witch make it difficult to solve the problem.
@seba.m
I wouldn't know where to start to modify the actual LCD driver board to adjust the PWM and BLO signal parameters. I don't know of any components on the driver board that are adjustable. And I am not a computer engineer or programmer with the skills or equipment to get into any of the internal coding of the chips on the board. Sorry I can't be of more help with that.
If the display brightness is a significant detractor using the Chinese boards, you could purchase an iMac inverter board separately and use it. They are not too expensive ($15-$20 US) on either AliExpress or Ebay. This would allow you to follow my guide.
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@seba.m
One quick point for clarification... I do not know if the connector to the TB display is the same as the connection to the iMac inverter. This is definitely something you will need to verify before purchasing an iMac inverter. I missed your "TB" in your original post. My apologies.
What a wonderfull noticed!. Im gonna use your guide. I buy the same pwm and step/down power module.
Im going to use your guide, I’ll write to you if any doubts come up. I see that it’s incomplete. I’ll do what I can to help you.
Hi @SubDriver maybe it's a good time to make a design of the connections between all boards to clarify some ideias? Even if it is hand draw. I can help sure 😊. On my project I discard the original Apple PSU because it's way cheaper to use/change if breaks a general PSU 5amp 12v and it's produces less heat.
@csdesign3 I agree. I already have one hand drawn, but it has become unreadable as I have made changes to it as I worked through my project. I am planning to include one in my final guide writeup, hopefully this weekend.
@csdesign3 @wujku and all others interested...
My bideirectional logic converter concept to restore display sleep funcitonality did NOT work. Although I got the correct signals delivered to the inverter board, the display would not fully turn on. At first, I thought maybe I had a loose connection or something else wrong. But after a couple hours of troubleshooting and verifying all the wiring, I could not find a reason. My best guess is the current supplied to the ENA pin was too weak to trigger the display.
I have reverted back to my original setup where the ENA signal is linked directly to the power button via a step down voltage converter.
After some additional research, I have ordered the following component for my next attempt: Adafruit 5648 MOSFET Driver
This solution uses a MOSFET whereby the MOSFET should be triggered by the BLO signal from the LCD driver board. This would then allow 3.3Vdc at nominal amperage to pass through to the ENA pin on the inverter board anytime the LCD driver board signals for the backlight to be energized.
The sad part is that I will have to wait another week for the MOSFET to arrive.
My bideirectional logic converter concept to restore display sleep funcitonality did NOT work. Although I got the correct signals delivered to the inverter board, the display would not fully turn on. At first, I thought maybe I had a loose connection or something else wrong. But after a couple hours of troubleshooting and verifying all the wiring, I could not find a reason. My best guess is the current supplied to the ENA pin was too weak to trigger the display.
I have reverted back to my original setup where the ENA signal is linked directly to the power button via a step down voltage converter.
After some additional research, I have ordered the following component for my next attempt: Adafruit 5648 MOSFET Driver
This solution uses a MOSFET whereby the MOSFET should be triggered by the BLO signal from the LCD driver board. This would then allow 3.3Vdc at nominal amperage to pass through to the ENA pin on the inverter board anytime the LCD driver board signals for the backlight to be energized.
The sad part is that I will have to wait another week for the MOSFET to arrive.
@SubDriver I make a simple design scheme in PNG, feel free to edit if you know if something its wrong about (this is my interpretation about your document). i dont use the 2 voltages step down (you can adapt to your document).
Attachments
@csdesign3 Your drawing is correct. I guess that means my guide is fairly clear!
I will post a complete diagram showing all internal components in the next few days after I return home from travel, to include the power and brightness control buttons, the speakers, cooling fans, and HDDs. Hopefully the MOSFET driver I ordered will resolve the display sleep function and I can include that in my drawing with confidence it will work.
Thanks@csdesign3 Your drawing is correct. I guess that means my guide is fairly clear!
I will post a complete diagram showing all internal components in the next few days after I return home from travel, to include the power and brightness control buttons, the speakers, cooling fans, and HDDs. Hopefully the MOSFET driver I ordered will resolve the display sleep function and I can include that in my drawing with confidence it will work.
I will improve the design quality (this is a quick Paint draft)Maybe the guide can include in the future the conversion of iSight camera and SD card reader to USB.
The time we already spent in searching information online well justifies the need to leave a well documented work i guess.
And again many thanks for your precious contribution.
Attached file has graphics showing the connections to the various components in my conversion.
I also attached an updated guide with the MOSFET driver instructions in case anyone else wants to try that. I should have my MOSFET driver in the next couple of days.
NOTE: The graphic on page 2 of the attachment is still not tested as I haven't yet received the MOSFET driver. Providing it for information only at this point. I will update this thread once I am able to confirm (or not) the sleep functionality with the MOSFET driver.
I also attached an updated guide with the MOSFET driver instructions in case anyone else wants to try that. I should have my MOSFET driver in the next couple of days.
NOTE: The graphic on page 2 of the attachment is still not tested as I haven't yet received the MOSFET driver. Providing it for information only at this point. I will update this thread once I am able to confirm (or not) the sleep functionality with the MOSFET driver.
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I may try to connect the SD card reader as part of my conversion in the future and will add that to the guide if I do that.Thanks
Maybe the guide can include in the future the conversion of iSight camera and SD card reader to USB.
The time we already spent in searching information online well justifies the need to leave a well documented work i guess.
And again many thanks for your precious contribution.
However, I don't intent to try to reconnect the iSight camera - it is such a poor quality compared to others available now. Additionally, with the ability to use an iPhone camera with a standalone Mac (mini or studio) through the iPhone Mirroring capability of Sequoia, it doesn't seem worth the effort.
If there are others that have done the work for the iSight camera, I can easily add those details to the guide if they are provided to me.
Hi Everybody. I am fairly new here so please excuse me if I have missed something. I am converting iMac A1312 and of course I do have the issue with the brightness. The display is LM270WQ1-SDC2 as the SDE3 model that came with the iMac I managed to physically break while trying to change the backlight as it had half black screen initially. So I have this idea based on post #113 to solve the sleep issue. I measured yesterday the voltage coming out of BLO/ENA and it is 5.08V. It should be good enough for the step down module to work (at least for the one I purchased) so instead of using one of the 12V wires for the step down module we use the BLO/ENA's 5.08V. This way when the controller disconnects the 5.08V supply the step down module stops the power supply to the PWM module and to the BLO/ENA of the original iMac inverter and the screen should go to sleep. Am I missing something? I have modified slightly the drawing from post #113 to show visually my idea. Please comment.
