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by AndyA
Wed Feb 06, 2013 7:33 pm
Forum: Other projects
Topic: 5" HDMI Touchscreen
Replies: 15
Views: 8239

Re: 5" HDMI Touchscreen

Curiosity question: Why go to SPI, then USB? Why not pipe the touchpad X-Y leads into an ADC and run it into the GPIO directly? Not meaning to criticize. I'm curious if you are aware of a GPIO issue that I haven't forseen? Just trying to expand *my* knowledge of modern technology. Using a trouchscr...
by AndyA
Wed Feb 06, 2013 7:23 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

OK. Warning note about the 3.5" board two posts up. That board runs some parasitic voltage doublers and inverters off the main switcher in order to generate LCD bias voltages required by certain display panels. Or in english - Depending on the exact display panel used in the unit you got it may not ...
by AndyA
Wed Jan 30, 2013 9:12 pm
Forum: Other projects
Topic: Powering a LCD car monitor
Replies: 11
Views: 3034

Re: Powering a LCD car monitor

So I may be able to power both the Pi and the screen directly applying 5V current? That could prove useful indeed. For now I'm just going to try again and be more careful with polarity. This isn't the thread you're looking for... http://www.raspberrypi.org/phpBB3/viewtopic.php?f=64&t=17651 ;-) I re...
by AndyA
Mon Jan 21, 2013 7:35 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

Two more board reworks, both of these will convert the existing input cable to 5V input. Note: outwardly there is no indication that the display is modified but connecting it to 12V will blow things up so if you have more than one display around make sure to mark it clearly. First a different board ...
by AndyA
Fri Jan 18, 2013 4:43 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

dooblem wrote:Well, but I don't know another way to make it work on 5v. Any other idea?
Sorry, not much help I can give without access to the circuit to poke around a bit.
by AndyA
Fri Jan 18, 2013 2:18 am
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

I think most work on about 5.25V, exactly where below that point they stop will vary board to board even for ones of the same design. The point of making the changes is to work from any USB voltage and also drop the current draw, running a switching regulator to convert 5 volts to 5 volts isn't very...
by AndyA
Fri Dec 14, 2012 1:41 am
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

Not shorting pins r36 and r37, loading those two parts with the correct value resistors as shown on the schematic. The cpu has a single usb port. On the B that goes to the lan chip which is also a usb hub. On the A it goes directly to the socket. Those two resistors link the cpu usb port directly to...
by AndyA
Thu Dec 13, 2012 10:51 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

It's the square one with lots of pins directly behind the USB ports. ;-)
Not exactly easy to get at with all the tall parts around it.
by AndyA
Thu Dec 13, 2012 6:22 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

i ran from my batterys to a step up transformer that suplied 1 amp to the rpi i then conneted the lcd to the gpio 5 volt output and it ran fine watched a film copyed files no problem i would be better with the a board as it dose not have lan but the memory is only 256 so i think i going to have to ...
by AndyA
Thu Dec 13, 2012 6:04 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

Just FYI: I'm using this pack http://www.newtrent.com/iphone-battery-imp60d.html and running both the Pi and the screen off the 1A rated output (the Pi has been modified so that the USB power in can be passed on to the screen bypassing any current limiting on the Pi). This then leaves the 2A output ...
by AndyA
Thu Dec 13, 2012 5:39 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

I bought a LCD just like this one and i'm thinking in doing this mod to use it with 5v feed. I know that the Pi needs something like [email protected], my question is: Using a 12.000mAh battery with an Output of 2.[email protected], can I power the Pi and the LCD with the same USB port on the battery? From what i've read,...
by AndyA
Wed Dec 12, 2012 6:39 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

Hi Andy, would you have a URL for the display? Maybe I am missing something, but the posts start with a reference to a display but there appears to be no link or even model description. Thanks! Johannes You have the forum set to the default colour scheme don't you? For some reason the default setti...
by AndyA
Sun Dec 09, 2012 4:06 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

You can power the display from the pi mk. 1 but you need to modify the board by tieing the power input directly to the usb power outputs. Bypassing the current limit protection isn't a good idea most of the time, it's there for a reason, but isn't hard to do if you need to save the space a hub would...
by AndyA
Wed Oct 24, 2012 4:00 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

It seems like there are many different board revisions out there, and I have one that nobody has documented before. http://jonty.co.uk/bits/screen_board.jpg The screen works fine when powered from 12v, but tapping into any available 5v points (including the spare through-hole connectors) results in...
by AndyA
Wed Oct 17, 2012 8:54 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

I see three models on the Amazon US website that are about $18. [...] Could someone who made this hack work with a product they bought on Amazon let me know which is the screen to order? Option 1 $17.99 Option 2 $19.70 Option 3 $18.45 Thanks. I've opened up both 1 and 3 and they are identical. I ha...
by AndyA
Wed Oct 17, 2012 1:31 am
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

However, what I don't understand is what do you mean by the 4 pins to the left? ... Additionally, id there a way to power this screen off of the pi itself without taking a usb port? I mentioned the two 4 pin parts on the left. They have 3 small pins on one side and one large one the other. These ar...
by AndyA
Tue Oct 16, 2012 3:09 am
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

However my control board is unlike yours, any idea which is the 5v resistor. The main regulator will be the bigger part in the top right. The 5V rail will go to one of those 3 large capacitors on the right, which one is impossible to tell from that photo. If you have a voltmeter it should be possib...
by AndyA
Thu Oct 04, 2012 10:43 pm
Forum: Other projects
Topic: Cheap 3.5" screen with touchscreen.
Replies: 3
Views: 5988

Re: Cheap 3.5" screen with touchscreen.

Update to account for my inability to count in the correct direction: I had the display ribbon cable back to front, pin 1 is the end one furthest from the driver IC, closest to the power supply and buttons. It looks like the touchscreen pins aren't connected to anything and are just floating. So it'...
by AndyA
Thu Oct 04, 2012 9:47 pm
Forum: Other projects
Topic: Cheap 3.5" screen with touchscreen.
Replies: 3
Views: 5988

Cheap 3.5" screen with touchscreen.

Want to add a touchscreen to your small display? The chances are you already have one and just don't know it. I posted previously how to convert this http://www.amazon.co.uk/gp/product/B0056WJP1M display to run from 5V rather than 12V. I was in the process of repackaging it into a smaller case when ...
by AndyA
Wed Sep 26, 2012 10:01 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

Would some thing similar to this work and adding the resistors as you have shown. I accept that Vgs does not have exactly what you suggested, but if I am on the right track then I will keep looking. http://www.irf.com/product-info/datasheets/data/irf7507.pdf The Vgs is fine, a lower threshold (mean...
by AndyA
Wed Sep 26, 2012 9:03 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

Everything is working fine! the resolution is not good to do much text coding as i think it will tire your eyes very quickly but for some quíck and dirty things should be fine. Haven't tried video! One thing I discovered was that changing the screen resolution to something closer to the displays na...
by AndyA
Wed Sep 26, 2012 8:54 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

James, Here's the schematic. https://dl.dropbox.com/u/25986954/schemeit-project.png The nice thing about FETs is that the current into the gate pins is 0* making them nice and easy to use. Q1 is a N channel with Vgs threshold of ~2V This means that until the voltage at the gate of Q1 is at least 2V ...
by AndyA
Mon Sep 24, 2012 11:19 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

I would like to be able to switch the display off using GPIO. Can any one suggest a circuit for doing this. The simple way is a total of 4 parts. Take an N channel MOSFET. Connect the gate to the GPIO pin, connect the source to ground and put a 1k resistor between the two. Now take a P channel MOSF...
by AndyA
Mon Sep 24, 2012 8:37 pm
Forum: Other projects
Topic: Modifying a 3.5" car display for USB power.
Replies: 453
Views: 233242

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

Could I also confirm, when the display is powered on, initially it flickers on then off again. Then after 3-4 seconds it detects the video input (From input 1 or 2) and switches on. Is this 3-4 second delay consistent with your models? Yes, an initial flicker then blank for ~4 seconds before it wak...
by AndyA
Mon Sep 24, 2012 6:33 pm
Forum: Other projects
Topic: 3.5 TFT Lcd Screen Problems.
Replies: 21
Views: 10510

Re: 3.5 TFT Lcd Screen Problems.

dteich02 wrote:I had a few problems running off of 250mA - are you sure thats going to work?
The two screens I've tested have used 300 to 380mA when running from a 5V source.
When running from 12V the current is about 180-200mA.

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