[GUIDE] 3.5 inch HDMI Display - high energy usage

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Re: 3.5 inch HDMI Display - high energy usage - WITH Fix

Post by McGyver » Thu Dec 07, 2017 1:55 am

For other like me which use a slightly different version if the KEDEI HDMI screen without the pushbutton for backlight setting: does these other KEDEI boards have a known way to change backlight brightness?

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Re: 3.5 inch HDMI Display - high energy usage - WITH Fix

Post by salami738 » Thu Dec 07, 2017 2:17 am

McGyver wrote:
Thu Dec 07, 2017 1:55 am
For other like me which use a slightly different version if the KEDEI HDMI screen without the pushbutton for backlight setting: does these other KEDEI boards have a known way to change backlight brightness?
Hi, there are two ways i can think of.

The RTH2660d (main big chip) has a pad for the backlight button. This has to be connected to GND via a switch, then you can set the backlight. You can look at the datasheet and solder a wire to this pin, if it isn't connected on your board. I have spare time this evening and will point you to the right pin, but you have to solder a very small area.

The second way would be to locate the parts that are used as the led backlight drivers and replace or mod them. I am currently working on this and will post a picture, if I have any new information.

Please post a high resolution picture of your board, so I can see which chips are used.

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Re: 3.5 inch HDMI Display - high energy usage

Post by Vineheart01 » Sat Dec 09, 2017 5:55 pm

salami738 wrote:
Wed Dec 06, 2017 1:42 pm
Hi,

maybe someone uses the hdmi screen too and want to squeeze out more runtime on batteries.
You can save about 25% power with this screen if you desolder the two AMS1117 chips.
There is one AMS1117-18 (supplies the 1,8V rail) and one
AMS1117-33 (supplies the 3,3V rail).
The display now uses the following currents on the rails:
1V8: 90mA (0,162W), 3V3: 145mA (0,479W) and 5V0: 170mA (0,850W). This is about 1,5W in sum.

Steps:
1.) desolder the two AMS1117 chips
2.) solder a cable on the middle pin of the pad (PIN 2) on both places
3.) solder the 3V3 cable to PIN1 or PIN17 on the raspberry zero w or PP9 on the raspberry zero
4.) solder the 1V8 cable to the 1V8 marked in my image
Image

Now you use the very efficient regulator of the PI to power the display and you will have a addition runtime of +25% on batteries! Have fun!

TODO:
- Find out why the display uses 0,85W on the 5V0 rail. Cant figure it out. Any help would be greatly appreciated.

greetings from germany
So if im understanding this right...

Image

Is this correct?
I wired it this way and my screen comes on but all i get is the Retropie splash screen followed by a solid blue screen over and over.
Last edited by Vineheart01 on Sat Dec 09, 2017 8:59 pm, edited 1 time in total.

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Re: 3.5 inch HDMI Display - high energy usage - WITH Fix

Post by Helder » Sat Dec 09, 2017 7:42 pm

Looking at the datasheet of the RTD2660 it has no 5V inputs so something else might need 5v on that board to make it function. Maybe look at the other chip datasheets for a clue.
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Re: 3.5 inch HDMI Display - high energy usage - WITH Fix

Post by salami738 » Sun Dec 10, 2017 4:20 am

Vineheart01 wrote:
Sat Dec 09, 2017 5:55 pm
salami738 wrote:
Wed Dec 06, 2017 1:42 pm
Hi,

maybe someone uses the hdmi screen too and want to squeeze out more runtime on batteries.
...
So if im understanding this right...

Image

Is this correct?
I wired it this way and my screen comes on but all i get is the Retropie splash screen followed by a solid blue screen over and over.
Helder wrote:
Sat Dec 09, 2017 7:42 pm
Looking at the datasheet of the RTD2660 it has no 5V inputs so something else might need 5v on that board to make it function. Maybe look at the other chip datasheets for a clue.
Hi, I checked the datasheets of every chip. The 5V0 rail is used for touch-controller, the audio dac and a flash chip (display firmware?).
And I am 75% sure the 5V rail is used for the backlight too (fourth chip? can't read the chip numbers on my board).
Later this day, I will measure the current drawn from this rail and if it is changing if the brightness changes.

I need a little more information about your setup to help you.
- Do you use a Raspberry Zero W or a Zero? (I tested it with a Zero W, which has the PAM2306 dual step-down ic)
- Can you check the current draw between the Raspberry and the Display 1V8 and 3V3 rail?
Should be very close to my values (90mA at 1V8 and 145mA at 3V3)
- Which settings did you use for the display in /boot/config.txt? I use 480x320 (native resolution). If you use a higher resolution, the current draw from the display would be much higher (according to the datasheet).
I use the following settings:

Code: Select all

# screen is not perfectly centered
overscan_left=24
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=87
hdmi_cvt=480 320 60 6 0 0 0
- Check your solder connections
- Check your HDMI cable / Replace with another one
- Check, if the raspberry is responding to SSH, if the connection to the display got lost
- Do you have a stable 5V power supply for all components? I tested with the banggood and a lab bench supply

I made two images from my build, maybe this helps:
Image
Image

greetings
Last edited by salami738 on Sun Dec 10, 2017 6:50 am, edited 2 times in total.

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Re: 3.5 inch HDMI Display - high energy usage - WITH Fix

Post by YaYa » Sun Dec 10, 2017 5:28 am

I really like how deep you are going in your build ! Thanks for sharing this with us :D
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Re: 3.5 inch HDMI Display - high energy usage - WITH Fix

Post by Vineheart01 » Sun Dec 10, 2017 8:41 am

salami738 wrote:
Sun Dec 10, 2017 4:20 am
Vineheart01 wrote:
Sat Dec 09, 2017 5:55 pm
salami738 wrote:
Wed Dec 06, 2017 1:42 pm
Hi,

maybe someone uses the hdmi screen too and want to squeeze out more runtime on batteries.
...
So if im understanding this right...

Image

Is this correct?
I wired it this way and my screen comes on but all i get is the Retropie splash screen followed by a solid blue screen over and over.
I need a little more information about your setup to help you.
- Do you use a Raspberry Zero W or a Zero? (I tested it with a Zero W, which has the PAM2306 dual step-down ic)
- Can you check the current draw between the Raspberry and the Display 1V8 and 3V3 rail?
Should be very close to my values (90mA at 1V8 and 145mA at 3V3)
- Which settings did you use for the display in /boot/config.txt? I use 480x320 (native resolution). If you use a higher resolution, the current draw from the display would be much higher (according to the datasheet).
I use the following settings:
CODE: SELECT ALL

# screen is not perfectly centered
overscan_left=24
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=87
hdmi_cvt=480 320 60 6 0 0 0
- Check your solder connections
- Check your HDMI cable / Replace with another one
- Check, if the raspberry is responding to SSH, if the connection to the display got lost
- Do you have a stable 5V power supply for all components? I tested with the banggood and a lab bench supply
Missed the code i needed for one, entered that in.
Apparently the Pie Zero W has a slightly higher power draw or something? I used the same initial setup i had with my last build before hooking the Powerboost up (hacked up USB cable feeding into a breadboard) and even with the screen detached it'd sit there rebooting over and over. Plugged it into the regular power cable and it didnt reboot.

Wired up my powerbooster and utilized that. Works just fine now.

Thanks for your help, i was confused on how to get this thing to work without utilizing the "intended" way. Unfortunately im still waiting on my slow boat from china for the hdmi stuff i intend to use so ... stuck again on this build :(
(i'm glad this worked because i accidentally shattered the 3V3 regulator when removing it lol)

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Re: 3.5 inch HDMI Display - high energy usage - WITH Fix

Post by salami738 » Sun Dec 10, 2017 9:36 am

Vineheart01 wrote:
Sun Dec 10, 2017 8:41 am
salami738 wrote:
Sun Dec 10, 2017 4:20 am
Vineheart01 wrote:
Sat Dec 09, 2017 5:55 pm
...
Missed the code i needed for one, entered that in.
Apparently the Pie Zero W has a slightly higher power draw or something? I used the same initial setup i had with my last build before hooking the Powerboost up (hacked up USB cable feeding into a breadboard) and even with the screen detached it'd sit there rebooting over and over. Plugged it into the regular power cable and it didnt reboot.

Wired up my powerbooster and utilized that. Works just fine now.

Thanks for your help, i was confused on how to get this thing to work without utilizing the "intended" way. Unfortunately im still waiting on my slow boat from china for the hdmi stuff i intend to use so ... stuck again on this build :(
(i'm glad this worked because i accidentally shattered the 3V3 regulator when removing it lol)
Thanks for your reply, so now we have two setups with this hack working!

The Pi Zero W has a higher current draw than the Zero because it has buildin WIFI and BT. You can disable that, if you dont need it via config.txt (didn't found a way to do it online without reboot).
Breadboards aren't designed to be used for high current draw, I think this was the problem.

Today I fried my arduino pro micro, so I have to wait for the slow boat too :lol:

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Re: 3.5 inch HDMI Display - high energy usage - WITH Fix

Post by Vineheart01 » Sun Dec 10, 2017 10:13 am

Oh im still using the breadboard but the power source is the powerboost 1000c instead of Random USB #1141 i had lying around i hacked up to expose the wires lol.
I'm guessing it wasnt able to supply enough power and once the Pie booted up enough programs it flipped out and rebooted. I didnt have that problem with my last build but my last build didnt have the wifi version and it was a BW screen.

Yeah i know i can disable the wifi and i'll probably do that when the build is finished but im a long ways from that.

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Re: 3.5 inch HDMI Display - high energy usage - WITH Fix

Post by salami738 » Wed Dec 13, 2017 1:28 am

@Vineheart01: Can you provide the model numbers of the four tiny chips on the board? Cant read the model number of the fourth and would like to know if this is the backlight driver.

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