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mahjongg
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Re: Modifying a 3.5" car display for USB power.

Sat Apr 18, 2015 12:33 pm

zKslol wrote: Any ideas what might be causing this? Any tips/a solution would be much appreciated! :-)
Yes, your cable reverses GND and the video signal, so the TV sees a negative signal.

Its in the common problems sticky: viewtopic.php?p=653422#p653422

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DougieLawson
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Re: Modifying a 3.5" car display for USB power.

Sat Apr 18, 2015 1:02 pm

Your 3.5mm plug has the AV signal and GND reversed.
http://www.raspberrypi-spy.co.uk/2014/0 ... ideo-jack/

Image
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zKslol
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Re: Modifying a 3.5" car display for USB power.

Sun Apr 19, 2015 5:58 pm

mahjongg wrote:
zKslol wrote: Any ideas what might be causing this? Any tips/a solution would be much appreciated! :-)
Yes, your cable reverses GND and the video signal, so the TV sees a negative signal.

Its in the common problems sticky: viewtopic.php?p=653422#p653422
DougieLawson wrote:Your 3.5mm plug has the AV signal and GND reversed.
http://www.raspberrypi-spy.co.uk/2014/0 ... ideo-jack/

Image
Thanks guys! Ordered a new cable last night :)

LunarScratch
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Re: Modifying a 3.5" car display for USB power.

Mon Apr 20, 2015 2:25 am

Hi all,

I recently purchased one of these displays for my GameBoy master system project, and I got the newer version with the small board. I've hooked up 5v power and ground, removed the regulator chip, as well as put the jumper between pin 3 (I've also tried pin 5), and I'm getting no signal from the display, not even a backlight. Do I need to hook up video signal before the display will even turn on?

BMS Doug
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Re: Modifying a 3.5" car display for USB power.

Mon Apr 20, 2015 12:05 pm

LunarScratch wrote:Hi all,

I recently purchased one of these displays for my GameBoy master system project, and I got the newer version with the small board. I've hooked up 5v power and ground, removed the regulator chip, as well as put the jumper between pin 3 (I've also tried pin 5), and I'm getting no signal from the display, not even a backlight. Do I need to hook up video signal before the display will even turn on?

That has occurred with some people's displays, check it with a video signal and it might work.
Doug.
Building Management Systems Engineer.

Tagiugy
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Re: Modifying a 3.5" car display for USB power.

Tue Apr 28, 2015 6:05 am

So I managed to fry my last screen and ordered another one. Surprisingly enough, the board was different. It looks just like sonami's at page 6.
When connecting 5V to one of the spots he mentioned, the screen flashes white and goes black.
Once I got the screen to work and saw retrostation's selection screen, but now I can't reproduce it :/
The composite video is forced, and I deactivated the hdmi hotplug. I know that my composite out is switched, the red cable is video, which I connect to the yellow cable of the screen.
My question is what you connect to the white cable of the screen? Is it needed at all, or is the yellow cable enough?

vxcheese
Posts: 6
Joined: Fri May 01, 2015 4:56 pm

Re: Modifying a 3.5" car display for USB power.

Tue May 26, 2015 11:58 pm

Can someone help me with this? I have this board:
Image
Keep in mind I didn't take this picture so I don't know why that chip is circled. I tried following the initial guide, and I removed the chip on the bottom left of the picture (near the push buttons). I'm not sure if that was the chip I was supposed to be going after.. If it is, where do I wire positive and negative into for USB power?

BMS Doug
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Re: Modifying a 3.5" car display for USB power.

Wed May 27, 2015 5:06 am

vxcheese wrote:Can someone help me with this? I have this board:

Keep in mind I didn't take this picture so I don't know why that chip is circled. I tried following the initial guide, and I removed the chip on the bottom left of the picture (near the push buttons). I'm not sure if that was the chip I was supposed to be going after.. If it is, where do I wire positive and negative into for USB power?
The circled and highlighted XL1509 chip is the voltage regulator, it could be regulating to either 3.3V or 5V depending on the board specifics. If it regulates to 3.3V then no modification is needed to the board, just connect the 5v power to the input power.

The chip you removed is probably an on-board memory of some kind and your board will not work without it.
Doug.
Building Management Systems Engineer.

MaK11-12
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Re: Modifying a 3.5" car display for USB power.

Wed May 27, 2015 10:58 am

Has anyone had any luck in changing the backlight brightness level?
I found that the voltage going to the 'K' and 'A' pins (the pins going to the backlight) on my 3.5" In-car LCD was a whopping 21.6V! This was whilst powering the LCD with 5V input after modding it with the instructions found in this thread. I have tried applying 5V to the K and A pins, but the backlight does not turn on at all.

My LCD uses up to 400mAh, which I want to reduce since it's going to be in a portable device. Anyone got any ideas?

Images showing the backlight pins and top-down view of the LCD circuit.
https://imgur.com/a/vY4Xh

Thanks.

BMS Doug
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Re: Modifying a 3.5" car display for USB power.

Wed May 27, 2015 11:14 am

MaK11-12 wrote:Has anyone had any luck in changing the backlight brightness level?
I found that the voltage going to the 'K' and 'A' pins (the pins going to the backlight) on my 3.5" In-car LCD was a whopping 21.6V! This was whilst powering the LCD with 5V input after modding it with the instructions found in this thread. I have tried applying 5V to the K and A pins, but the backlight does not turn on at all.

My LCD uses up to 400mAh, which I want to reduce since it's going to be in a portable device. Anyone got any ideas?

Images showing the backlight pins and top-down view of the LCD circuit.
https://imgur.com/a/vY4Xh

Thanks.
Perhaps you could break into the line, add a transistor and use PWM to reduce the brightness?
Doug.
Building Management Systems Engineer.

MaK11-12
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Re: Modifying a 3.5" car display for USB power.

Wed May 27, 2015 11:18 am

BMS Doug wrote: Perhaps you could break into the line, add a transistor and use PWM to reduce the brightness?
I've never used transistors before, so I'm unsure how your idea would work. Would I connect the 21.6V input and a PWM signal to the transistor, and the transistor would then output a voltage depending on the PWM signal?

Edit: I found this post to be of some help: http://www.instructables.com/id/Use-Ard ... trol-moto/
Thanks a lot for the idea. :)

BMS Doug
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Re: Modifying a 3.5" car display for USB power.

Wed May 27, 2015 12:42 pm

MaK11-12 wrote:
BMS Doug wrote: Perhaps you could break into the line, add a transistor and use PWM to reduce the brightness?
I've never used transistors before, so I'm unsure how your idea would work. Would I connect the 21.6V input and a PWM signal to the transistor, and the transistor would then output a voltage depending on the PWM signal?

Edit: I found this post to be of some help: http://www.instructables.com/id/Use-Ard ... trol-moto/
Thanks a lot for the idea. :)

I would suggest that you break into the Gnd line from the backlight, connect the transistor Emitter to 0v (board ground), the transistor collector to the 0v line coming back from the backlight and the transistor base to the Pi GPIO (through a current limiting resistor).

The TIP 120 is indeed a good choice for this application.
Image

By controlling the backlight with Pulse Width Modulation you will rapidly turn the backlight on and off, reducing the load and brightness accordingly. This will give you a usable brightness control that you will be able to adjust from the Pi.

Use Joan's PIGPIO library for controlling the PWM output.
Doug.
Building Management Systems Engineer.

cleathy
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Re: Modifying a 3.5" car display for USB power.

Wed May 27, 2015 5:54 pm

Hi i need some help converting this board to 5v

Here is some pictures:

Image

Image

This is the item i bought:
http://www.ebay.co.uk/itm/331040572849? ... EBIDX%3AIT

BMS Doug
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Re: Modifying a 3.5" car display for USB power.

Wed May 27, 2015 6:32 pm

cleathy wrote:Hi i need some help converting this board to 5v

Here is some pictures:

Image

Image

This is the item i bought:
http://www.ebay.co.uk/itm/331040572849? ... EBIDX%3AIT
The first thing to do is to identify the operating voltage, the voltage regulator chip is capable of outputting a range of voltages so first you need to identify what it is putting out.
Doug.
Building Management Systems Engineer.

cleathy
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Re: Modifying a 3.5" car display for USB power.

Wed May 27, 2015 10:19 pm

BMS Doug wrote:
The first thing to do is to identify the operating voltage, the voltage regulator chip is capable of outputting a range of voltages so first you need to identify what it is putting out.
Alright, heres is what i got from my readings

Image

(if the text is too small, i can make it bigger)

BMS Doug
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Re: Modifying a 3.5" car display for USB power.

Thu May 28, 2015 8:06 am

cleathy wrote:
BMS Doug wrote:
The first thing to do is to identify the operating voltage, the voltage regulator chip is capable of outputting a range of voltages so first you need to identify what it is putting out.
Alright, heres is what i got from my readings


(if the text is too small, i can make it bigger)
The Text is clear enough, That's a BM1410A not a MB1410A as you wrote.

Pin 3 (the pin that is at 4.59 Volts) is where you will need to connect the 5V power supply.


The other chip in an internal memory and should be left alone.
Doug.
Building Management Systems Engineer.

cleathy
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Re: Modifying a 3.5" car display for USB power.

Thu May 28, 2015 8:49 am

BMS Doug wrote:
cleathy wrote:
BMS Doug wrote:
The first thing to do is to identify the operating voltage, the voltage regulator chip is capable of outputting a range of voltages so first you need to identify what it is putting out.
Alright, heres is what i got from my readings


(if the text is too small, i can make it bigger)
The Text is clear enough, That's a BM1410A not a MB1410A as you wrote.

Pin 3 (the pin that is at 4.59 Volts) is where you will need to connect the 5V power supply.


The other chip in an internal memory and should be left alone.
Okay. Should i remove the chip too?

BMS Doug
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Re: Modifying a 3.5" car display for USB power.

Thu May 28, 2015 2:45 pm

cleathy wrote:
BMS Doug wrote: Pin 3 (the pin that is at 4.59 Volts) is where you will need to connect the 5V power supply.

The other chip in an internal memory and should be left alone.
Okay. Should i remove the chip too?
The original post on this thread recommends removing the voltage regulator chip, some people have said that they got theirs working without removing the chip. I guess it's up to you, I personally would remove the chip (as I would worry about what the chip was doing while we abuse its designed function).
Doug.
Building Management Systems Engineer.

cleathy
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Re: Modifying a 3.5" car display for USB power.

Thu May 28, 2015 10:01 pm

BMS Doug wrote:
cleathy wrote:
BMS Doug wrote: Pin 3 (the pin that is at 4.59 Volts) is where you will need to connect the 5V power supply.

The other chip in an internal memory and should be left alone.
Okay. Should i remove the chip too?
The original post on this thread recommends removing the voltage regulator chip, some people have said that they got theirs working without removing the chip. I guess it's up to you, I personally would remove the chip (as I would worry about what the chip was doing while we abuse its designed function).

Alright, thank you! I'll try that (:

jay_hart
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Joined: Sat Jun 06, 2015 11:54 pm

Re: Modifying a 3.5" car display for USB power.

Sun Jun 07, 2015 12:24 am

Hey everyone. I've recently acquired the same lcd screen from Amazon but it seems my board hasn't been worked on before here.
Image
Image

I'm trying get this working as a portable screen for my raspberry pi running retropie. I've purchased an Adafruit Powerboost 500 Basic and a Mini Lipo charger. I plan on using a 3.7v battery thats why I added the Powerboost. The picture above is my current setup. No battery at the moment so just a usb cable hooked up to where the lipo charger would recharge the battery. All I can manage to do however is get the screen to lightly flash when I first plug in the usb and thats it. I have a video line on Video 1 so that isn't the issue. I've read through what you guys have come up with and found 5v coming out through where I currently have the red and black cable going through but no dice. Any suggestions??

Chillman90
Posts: 4
Joined: Sat Sep 07, 2013 8:35 am

Re: Modifying a 3.5" car display for USB power.

Sun Jun 14, 2015 3:08 pm

Hello!

I also bought a slightly different display from eBay:
http://www.ebay.de/itm/331113587110?_tr ... EBIDX%3AIT
Which sadly didn't work from the beginning on. However it has a very small circuit board.

So I've opened it and found out, that one of the flex cables seems broken (red circle in the picture).
Though the seller is refunding the money, I'm curious if it is possible to fix and modify this display for the use with 5V.
If it is not fixable I have to buy a replacement and I could order the same type if it will work with 5V.

What do you think? Looking forward to any ideas. :D

Circuit board:
https://www.dropbox.com/s/l04b97d3h9h67 ... 0.JPG?dl=0
Attachments
IMG_0181.JPG
IMG_0181.JPG (59.31 KiB) Viewed 5071 times
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$_12.JPG (25.93 KiB) Viewed 5071 times

cheezyguy5
Posts: 8
Joined: Wed Jan 08, 2014 2:53 pm

Re: Modifying a 3.5" car display for USB power.

Sun Jul 05, 2015 8:49 pm

Chillman90 wrote:Hello!

I also bought a slightly different display from eBay:
http://www.ebay.de/itm/331113587110?_tr ... EBIDX%3AIT
Which sadly didn't work from the beginning on. However it has a very small circuit board.

So I've opened it and found out, that one of the flex cables seems broken (red circle in the picture).
Though the seller is refunding the money, I'm curious if it is possible to fix and modify this display for the use with 5V.
If it is not fixable I have to buy a replacement and I could order the same type if it will work with 5V.

What do you think? Looking forward to any ideas. :D

Circuit board:
https://www.dropbox.com/s/l04b97d3h9h67 ... 0.JPG?dl=0
That flex cable is broken, and flex cables cannot be reattached at all. I suggest you try to return that.

Otherwise, I believe the voltage regulator is the small black chip just below the white cable connector in the top left of the board. But you should use a multimeter to test the voltages just to be safe. If the output is 3.3v then you can just hook it up to a 5v source without a problem, if it's 5v then you'll need to solder a cable to both GND and +5v and run your 5v source through those wires. That chip should not need to be removed.

tinylcd
Posts: 206
Joined: Sat Oct 26, 2013 4:07 am

Re: Modifying a 3.5" car display for USB power.

Mon Jul 06, 2015 4:23 am

Hello

incase you are planning to buy the one which works on 5 volts

and the 5 volt power adaptor included in the price

than you can have a look at below product

http://www.neosecsolutions.com//product ... 8&cPath=21

regards
tinylcd

Chillman90
Posts: 4
Joined: Sat Sep 07, 2013 8:35 am

Re: Modifying a 3.5" car display for USB power.

Sat Jul 11, 2015 7:39 am

Hello cheesyguy5 and tinylcd,

I just received an other LCD which I ordered before you answered tinylcd (sorry) and tried to use that one instead. It appeared to have the same problem. By chance I found a 5V-source from a broken USB-Hub and tried running the LCD with that one and it worked. :D
So I tried that source with the old LCD (with the apparently broken flex cable) and it worked, too. So I probably have to blame the adaptor of the powersource.

So both displays work with 5V. :D

This is the link to the newer working LCD:
http://www.banggood.com/3_5-Inch-Digita ... 74587.html

Thank you for your tipps!

cheezyguy5
Posts: 8
Joined: Wed Jan 08, 2014 2:53 pm

Re: Modifying a 3.5" car display for USB power.

Mon Jul 13, 2015 3:10 am

Chillman90 wrote:Hello cheesyguy5 and tinylcd,

I just received an other LCD which I ordered before you answered tinylcd (sorry) and tried to use that one instead. It appeared to have the same problem. By chance I found a 5V-source from a broken USB-Hub and tried running the LCD with that one and it worked. :D
So I tried that source with the old LCD (with the apparently broken flex cable) and it worked, too. So I probably have to blame the adaptor of the powersource.

So both displays work with 5V. :D

This is the link to the newer working LCD:
http://www.banggood.com/3_5-Inch-Digita ... 74587.html

Thank you for your tipps!
:shock: You got insanely lucky, man! That broken flex cable must have been some kind of non-essential connector, otherwotherwis you would've seen a mess of interlacing.

If it ran off of the 5v adapter, then the thing is running at 3.3v, another great stroke of luck because that requires no modding.

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