Remake.IT – Raspberry Pi 3 with 7″ Touch Screen and housing

A while ago, I bought a couple of the new Raspberry Pi 3’s and at the same time, bought a 7″ touch screen and a housing (which was on special) for it from element14.

http://au.element14.com/raspberry-pi/raspberrypi-display/raspberry-pi-7inch-touchscreen/dp/2473872

http://au.element14.com/multicomp/cbrpp-ts-blk-wht/raspberry-pi-touchscreen-enclosure/dp/249469102

As usual, there can be a delay between purchase and actually assembly or use, due to other commitments. Anyway, a couple of nights ago, I decided to assemble the Raspberry Pi with the touchscreen. The touchscreen was pre-assembled, so all that I had to do was to attach the screen cable to the Raspberry Pi 3, then connect the four wires to provide power and the data signals to the touchscreen controller board. By the way, the instructions did not say that the SDA and SCL signals had to be connected and showed only connecting the ground and +5V pins.

I also needed to download the latest Raspbian operating system, and copy the image to a micro-SD card which I did the next day. Then finally plugging in the card, and fastening the Raspberry Pi down with four tiny screens. Next was placing all this in the housing. All went together and I connected up a suitable power supply and powered up.

Voila! Hmm, the display is upside down – ok, and the touchscreen wasn’t working. Checking out the FAQ on the appropriate sites indicates a fix for the display – to rotate by 180 degrees in the /boot/config.txt then a check to see if the touchscreen hardware was seen by the OS. ¬†Yes, the drivers are active so what is going on? I decided that it was time to open it up and check the touchscreen cable.

To my surprise the cable was disconnected and sticking up at a right angle – then the penny dropped. Putting the case on, must have disconnected the cable, which was connected, but now is not.

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This is the touchscreen cable, the one that is attached to that black square chip – the cable is a little bent at the edge which meant that something was pressing on it. Turning the back of the case around showed me the problem.

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The cutout for the touchscreen cable has a sharp edge, which was pressing down on the edge of the touchscreen assembly with the chip on it, and since the thinner cable is not that long, pushing down on it would pull that thin cable out. Which is what must have happened. I measured the distance from the edge of the case to that touchscreen assembly, then marked on the case where I needed to remove that sharp edge. I got out my trusty file which happened to be almost the right width at the area I needed to file out, and proceeded to remove some plastic material making that marked area more rounded which would reduce the pressure on that assembly.

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Here is the final result. After careful reassembly and checking of the cable which was can just see through slots in the casing for the HDMI socket, I can confirm that the touchscreen cable is still attached.

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After powering up, I now have touch!

 

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Replace.IT – LCD Screen for Compaq Presario V6002AU

I had this Compaq Presario V6002AU 15.4″ laptop sitting around for a little while – as they do. This laptop had a bad lcd screen, in that the display is dim and doesn’t look like anything is recognizable. I had taken it apart to check the screen. I have a copy of the Maintenance and Service Guide for this laptop. This guide shows how to open and replace parts of the laptop and is a must-have if you are to do this properly without damaging any of the plastics or component boards. Most of the time, these guides are quite accurate – and occasionally they might leave out an instruction or two, like in this case, remove the front panel switch cover requires removing three screws instead of two screws.

Ok, that isn’t the topic of today’s post – but the lcd screen is. The Compaq spare part number for the lcd screen is 431386-001, which is with BrightView, i.e. glossy. I duly went on Google to check whether this panel was available, and found a local supplier on eBay that had this for $81.99 including free postage. Ok, so I ordered it, and when it arrived, I noticed that the backlight cable was a little short. I compared panel part numbers – my original panel is a LG Philips LP154W01 (TL)(AE). The replacement panel is a LP154WX4 so I contacted the seller and we conversed via eBay and email. Anyway after explaining that the backlight cable was too short by about 2cm, I asked whether or not they had a LP154W01 (TL)(AE) in stock.

They came back to me by asking me to cut the backlight cable, and take the old backlight cable and join it to the replacement panel, and that way it should reach. I replied that this is not recommended especially since the backlight voltages are very high, usually from 500 to 900Volts. The wires have silicone insulation and if I do cut it and repair, it can form a leakage point, whereby some of the time, the display becomes dim, due to the backlight not lighting properly. Not to mention voiding the panel warranty if it should fail and then they say that the panel has been tampered with. Anyway, the solution to this eBay panel is that they asked me to send it back and they will refund me.

Now, I could find the required panel, but at a higher price, about $115 – but then it isn’t really worth it. I decided to scrounge around my old broken laptops and eventually came across a Compaq Presario V4000 with the same size screen. Ok, maybe I can use this so proceeded to remove the screen from the laptop. This screen is a LTN154X3-L01 – however the backlight cable is long enough, and the lvds connector is in the right place. I obtained the datasheet for this screen, and confirmed the pin configuration of the lvds connector is the same and the original screen. The resolution is the same, so how about I try it out? I connected this screen temporarily and powered on the laptop and was greeted with a Compaq power up screen, ok – great, so switched off and proceeded to install the screen properly.

After everything was put back in place, I had zero screws left over – always a good feeling. I power up and it wouldn’t power on – now what. Then I realize that maybe the battery is flat. It just happens that one reason I wanted to resurrect this laptop is that it uses the same battery as a HP Pavilion laptop that we had had for many years, which I have a spare battery for. I grabbed the spare battery and put it in and powered on – success, the laptop booted into Windows XP Professional. This laptop only has 1GB of ram and can handle up to 2GB maximum. I think I will use this as my Windows 10 test machine, or perhaps just run Linux on it.

The moral of the story is that quite often lcd screens from different laptops can be compatible as long as the lvds connector is the same and it is located in the right place. This one had a 30 pin lvds connector, but it is always good to compare pin configuration just in case one screen doesn’t use the standard wiring – don’t want to damage a good screen or damage a laptop motherboard.

P.S. No pictures, since a working laptop is … a working laptop.