Zipit Back Light
Contents
Adding a backlight to the Zipit
04.26.05ZipIt backlightPosted in Hackery at 11:53 pm by rob http://constructiveinterference.net/archives/date/2005/04/
I added an EL backlight to my new ZipIt last week, using the EL panel I got from Miller Engineering and an EL driver board from Jelu. It’s really a shame that manufacturers continue to ship devices without a backlight; it’s often the kiss of death for products that otherwise might develop a following. I might eventually add a serial port like the one on Matt’s for GPS / Bluetooth / EVDO goodness…
But for now adding the backlight and a decent linux distribution actually turns this little toy into a useful terminal. SSH gets you to most utilities (pine for mail, snownews for RSS, links for web, etc), and IRC is built-in. You get three virtual consoles to play with (alt-P1 to alt-P3), which is quite nice. Once I get Kismet going, this will be a killer little wireless gadget.
Here’s a step-by-step account of how I added the backlight. No, I won’t buy you a new ZipIt if you break yours while attempting this.
Step 1: Get it open
Flip the little guy over. Unscrew the battery cover and yank the battery. Pry up the tiny rubber feet to reveal four Phillips head screws. Remove them. The entire bottom should come off easily. On my unit, the sticker covering the battery area was stuck to the CPU, so you might have to gently pry that up with a screwdriver. Be careful as you pull the bottom off, as the speaker is attached to a recess in the bottom with gummy glue. Pry up the speaker and completely remove the bottom shell.
Be careful not to lose the power button cover. Take it off and put it where you put the case screws (and don’t lose those either.)
Step 2: Remove the mainboard
You’ll need a soldering iron for this step. First, apply heat to the antenna connector cable and remove it from the board. Next, gently, lift the white hinge of the plastic LCD connector and the keyboard connector, gently remove the ribbon cables.
Remove the mainboard and put aside, BUT, put the board face down (component side down). You need to protect the tiny little cover switch on the bottom of the board, it is easily damaged
Step 3: Open the LCD
Open the ZipIt lid, and remove the teeny rubber discs on the inside of the hinge. Remove the exposed Phillips head screws.
Leave the ZipIt open and flip it back over. Near the brown LCD ribbon cable you should see three more Phillips head screws. Two are connected to the metal pivot hinge. Leave those in place. Remove the third screw, which will release the small cap covering the ribbon cable and antenna feed. There was also a tiny pink plastic clip jammed into this space on my unit, putting pressure on the cables. Remove and discard it. Since we’ll be adding a power cable for the backlight here, you won’t have enough space for it, and since it just chafes the cables anyway you won’t miss it.
Now the tricky part. You have two possible start areas, one being at the latch of the zipit’s LCD (easier and better safty margin I think). The other is described later in this section part 3 of the document. Read all of step 3 before you try any thing. Don’t worry you will not get the LCD lid cover off with out putting a few good dents and dings into the seams of the two halves.
For the latch method, it’s assumed you have removed the rubber covers and two screws under them on the LCD screen. Be ware when you separate the two Halves of the lcd lid the latch and spring may fly out. Remove them and place them in a safe area, you will not be happy if you put your LCD lid back together only to find you forgot or lost the latch parts.
You need two very small flat head screw drivers to perform this mod. The idea is to take a very small screw driver and insert it into the small hole to the right of the LCD lid latch (this is the thumb lever area used to open the latch). You need to enter the screw driver as close to parallel with the edge of the zipit as possible (DO NOT DRIVE IT STRAIGHT IN, enter the screw driver at an angle and very very shallow at that). Next you pry down separating the two halves of the LCD lid. Using the second small screw driver you need to pry the TOP half of the lid cover forward and away from the zipit. That means put the screw driver in to the space and then angle the handle down. The little snap latch seal will release, continue this all the way around the zipit LCD lid. The bottom center latch is a royal pain to release, you have been warned.
For the hinge method start from one of the hinge corners, I start with the one with the wires dangling out it. Slip your thumbnail between the two halves and slide your thumbnail across to the next corner. The hinge clips should gently pop loose. Slide all around until the final corner next to the opposite hinge is opened. Beware, the clip at the bottom has to be "levered" open, it is not a snap clip.
Also, be very careful when prying this apart not to lose the lid latch and spring. You can probably live without them, but if you want to keep them, now is your chance not to let them fly across the room or fall behind the workbench.
Step 4: Remove the LCD reflector
If all went well, you should see the white backing of the LCD panel, as well as more brown ribbon cable and the lid antenna. The white backing is held to the LCD with a sort of thick rubber cement. You need to peel this backing off and replace it with EL panel. The cement will stick to the LCD. Keep in mind that there is a polarized sheet on the back of the LCD. You must only remove the "paper thin white/silver reflective sheet", and not this polarized sheet, or your LCD will not work until you replace the polarized sheet with the original or a new piece.
Pick at a corner of the backing with a razor blade (or a fingernail). Try to peel off the backing all in one piece, pulling firmly away from the LCD. Keep in mind that the LCD is made of glass and is very, very fragile. Start your peel from the foil side of the LCD, not from the antenna side, keep a little finger pressure on the foil to keep from popping the display out of the cover.
When the backing has been removed, there will be a cloudy film left over. You can remove this by rubbing a clean finger (thumb works better) on the films. It will ball and roll off after a while. When all the glue has been removed, clean the back of the screen with alcohol and a lint free cloth. It’s not a quick project but will leave you with a clean clear screen, perfect for the backlight mod. And remember the screen is frail glass do not push down very hard hard or bad things will happen.
Also refrain from the temptation of using a fingernail to remove the adhesive. You may scratch the polarized filter.
There is a good reason for taking the time to remove this adhesive. If you stick the backlight material to the adhesive, it will leave the display a dark gray. This is due to the light that the reflector used to "reflect" (heh), now a lot of that is absorbed by the EL material. When you are using the ZipIt in lighted environ, the display would look "dark". Removing the adhesive, the display is much "lighter" in color (light grey) even when powered off.
Step 5: Prepare and install the EL panel
You should now be able to estimate how much EL panel you will need to cover the LCD. Trim yourself a nice piece using a pair of scissors. It should overlap the LCD panel on three sides by a couple of millimeters. On the side nearest the antenna, leave one set of leads and trim off the rest.
Consider taping the edges of the backlight down so it doesn't shift while assembling the cover.
Step 6: Wiring
Solder a couple of wires to the leads on the EL panel. I used ribbon wire salvaged from an old floppy disk cable. It should be at least 8 or 9 inches long, preferably stranded, and as thin as you can find (recycled CAT5 cable is way too thick). Remember that plastic will melt if you’re not careful with your soldering, so be quick.
Run this wire the same way the antenna wire is run. Cover the exposed leads on the EL panel with a piece of electrical tape.
Flip the ZipIt back over, and put the mainboard back in place. Feed the antenna cable and the two wires through the hole closest to the LCD panel connector.
Now comes the fun part: soldering the leads to the mainboard. Attach one wire each to the plus and minus poles on the battery connector. Solder a third wire to the corner pin on RP4, on the R108 side closest to C116. Here’s a detailed photo with the proper pin labeled EN.
Finally, reattach the antenna lead. When you’re done, it should look something like the photo on the left. If your soldering iron isn’t fine enough to solder the third wire, don’t panic. This pin is pulled high when the LCD panel is active, so once we figure out power management on the board, this wire will turn the backlight on and off when the lid is closed. Of course, we haven’t figured out power management as of this writing, so the backlight stays on all the time anyway (unless you’re running the ZipIt messaging client, in which case it works beautifully.)
If you can’t get this wire attached without destroying the board, just connect that wire directly to power and the backlight will stay lit all the time. Not ideal, but better than nothing.
Step 7: The driver board
Now solder in the EL panel driver board. The driver board from Jelu is based on the Supertex HV857MG driver (it’s pretty much a nice little implementation of the reference design.) I’ve noticed that this chip isn’t designed to drive a panel as big as the one for our ZipIt, so it ends up being a mellow blue instead of bright white. If you change the chip to an HV826 or HV830 (see the data sheet link above), it should be much brighter. I’ll likely give that a try at some point.
Connect LA and LB to your EL panel (it doesn’t matter which is which), and connect GND to minus, VDD to plus, EN to the remaining wire. At this point, you probably will want to connect the battery and power up the ZipIt to be sure that everything works as expected. Don’t touch the driver board while it’s on unless you are partial to electric shocks for fun.
If all went well, completely cover the driver board in electrical tape and carefully reassemble the ZipIt. There’s plenty of room for the driver board in the channel next to the battery compartment.
Conclusions
Installation is the reverse of removal. ;)
Congratulations, you can now use your ZipIt in lighting other than direct bright sunlight
I’m definitely going to try a different EL driver chip to get the brightness up a bit. But the Jelu model should get you going. These things are really neat; you typically need a big, whiney transformer to drive EL, but these driver chips are small, quiet, and efficient. A tiny driver board combined with a light that you can cut with scissors to any shape should make it easy to add a backlight to just about any transparent LCD display…
Blogged in /seattlewireless/hacknight by mattw Monday April 11, 2005 at about 6:14 pm
Adding a backlight to the Zipit is a bit more advanced than the 5 wire serial mod on the Aibo Hack page, but is still do-able for your average hardware hacker. In my opinion, this makes the device much more useable, and of course, with your choice of EL colors, gives you a bit of personal bling.
The first thing that you need to do is order some parts. The Jelu Web Shop has an awesome little EL Backlight Driver that is smaller than any of the driver kits available at the EL outlets I found on google. http://www.jelu.se/shop/product_info.php?manufacturers_id=10&products_id=33 Second, you’ll have to get a piece of EL Panel. I ordered a nice red panel from Florida, but of course, it wasn’t in stock. Rather than wait around for the postman, I ripped apart a Virtual Bartender I had laying around (christmas gift?) and gutted it for it’s panel. It’s a little short, but hey, it’ll work until the red one shows up.
The EL Backlight Driver comes with a schematic, and this page has instructions for soldering to a yampp. http://www.myplace.nu/mp3/backlight.htm For the Zipit, you’ll need to connect the EN pad on the board to RP4 on the Zipit motherboard. http://imob.org/zipit/zipitboard_backlight This will make the backlight shut off when you close the lid (running Zipit application only, Linux blanking is not supported yet). It’s a bit of a tricky connection, so I had Rob do the soldering here. Thanks Rob
The LCD in the Zipit has a peel-off backing, so you can just peel that off and stick your EL on. I actually removed all the gummy bits with some goof-off, but I think it may have been an unnecessary (and brain cel killing) step.
With all of these mods, the wire snaking will be your own personal nightmare. I suggest you don’t use bits of Cat5 and go with a lighter gauge solid core wire. Or a flat ribbon cable cut down to 2 connected strands from a printer heads driver ribbon cable or the ribbon cable from an old scanner. The idea is high voltage low current, current equals heat. High voltage equals arking emitions by jumping like a static shock. The thicker the wire coating the better. You will also want to put upto but no more then two coils in the hinge area as strain relief on the high voltage wires for driving the backlight.
