20" iMac G4 Pro - Touchscreens

After a break, I am back and have several projects which I am starting to organize for.

1.  The 17" TMDS to DVI, including Video Tutorial has been completed.

2.  For the 17", I am thinking about finishing this up in some fashion.  This would not be an all in one, but instead may use wireless DVI and function as a second monitor.

3.  Apple Cube mod.  After searching I have seen some amazing cube mods including newer ones which use the existing heatsink.  This makes me somewhat less enthusiastic, as it has been done already, but it is still something that I would like to do using my core 2 duo ECX board.

4.  The 20" iMac G4 Pro Mod.  As I talked about in an earlier post the features that I would add to this pro mod would include, in order of importance:

A) Touchscreen: Something I have tried to incorporate since my first iMac G4 Mods

- The problems that I've had relate mostly to the fact that 20" 16:10 is no longer a common size.

- Touchscreens often add extra weight and thickness and thus complicate the designs

- Available Touchscreens are often of poor quality and use resistive technology that is not multitouch compatible and often detracts from the image by adding a reflective glare.

B) LED Backlighting: This conserves power and can allow for a much thinner LCD enclosure.

- Similar to the Touchscreen this is complicated by the odd 20" 16:10 aspect ratio.  No commercially available LED LCDs are available in this format.

- This may also allow for brightness control with a PWM control.

C) Upgraded Processor, RAM, and improved cooling: You can't have the first two without the third.

- I tried to make my previous mod as close to the original as possible, with the optical drive, space is somewhat limited and to ensure stability with the existing heatsink I went dual core i5

- To use a quad core, I will have to upgrade the cooling in place of the optical drive.

D) The native PSU: Resourceful readers have incorporated the native PSU.  

- Unfortunately, the native PSU did not fit my previous mod.  Without the optical drive and with improved cooling, I should be able to use the native PSU.

E) An iSight/Mic: Although the mic exists the rotating, tilting LCD makes the G4 ideal for an iSight.

- I do not yet know if a newer iSight will work better than the one from the iMac G5.  I already know how to turn the iSight from the G5 into a USB compatible camera, but I don't know if it will fit.

F) Aesthetic Changes: While rigs with neon lights all over were never my taste, I wouldn't mind some LED lights to differentiate this mod.

To start with, the most important thing I would like to incorporate is a Touchscreen.  Several of my iMac G4 mods have incorporated touchscreens.  I do agree that desktop touchscreens are not ideal, but in certain situations they can be quite useful.  A prerequisite is that the must be able to tilt backwards - newer touchscreen all in ones are doing this and apple's own patent shows that they have considered this approach in a design that is very reminiscent of the iMac G4 (mixed with the current iMac design).

Courtesy of patentlyapple.com

Rear View

Unfortunately, the extra girth and weight of the 20" touchscreens required significant compromise in the design.  I used a shell from an aluminum 20" cinema display and the front bezel of the G4.

At the time I hadn't yet figured out how to use the native inverter, so using the ACD solved both of these problems.  Once I figured out how to use the native inverter, I was able to use the complete original G4 shell and came to prefer the native appearance over my design despite the touchscreen.

Part of this had to do with the 5 wire resistive touchscreen which I found myself having to recalibrate frequently and had an annoying reflective glare.

However, with newer operating systems favoring touch/tablet interfaces over traditional Mouse/Keyboard, having a rotating. bending, tilting, floating touchscreen seems like the best possible type of desktop to try this on.  Lion (and even more so Mountain Lion) is actually touch friendly especially from the Launchpad interface.  Windows 8 Consumer Preview is even more touch friendly in that not using a touchscreen seems wrong.

I have an image of a broken 20" iMac G4 that will serve as the skeleton of this project.  The previous owner tore the front bezel off.  What you will notice is that the LCD comes right to the front of the enclosure.  Sure, you could put a touchscreen in front and secure it with double sided tape and the tape on the front bezel, but there would be a visible space from the side.  Plus, as you'll be moving and touching this, I worry about keeping it secure.  But, you can see that as is, adding anything in front of the LCD is difficult.

I have gone to great lengths to consider various touch options that are available, even inquired about custom touch screens.  The 20" 16:10 continues to be a difficult size to find.  There is a 20" 16:10 Surface acoustic Wave Touchscreen that I used in the past, but it requires a border that goes beyond the dimensions of the enclosure.  So that leaves these four:

Top Left is a broken 21.5" 16:9 optical touch monitor (LCD is broken by the touch aspect works).  This uses optical sensors in the corners and does require a "gap" in front of the LCD.  Can I adjust this to 20" 16:10?

Bottom Left is a 5 wire resistive touchscreen.  This is the same company that manufactured the screen for my old mod, but they have added an anti-reflective coat.  Its fairly light and thin and the correct size and ratio, but I still have reservations regarding resistive technology in general.

Top Right is an IR 19" 16: 10 touch panel.  The IR sensors are corrected in the corners and it may be possible to extend this connection.  Again, this requires a "gap" and I will likely loose touch sensing in the 4 corners.

Bottom Right is a 20" (approx 16:10) capacitive panel that I obtained from 3M.  Its an older cap active technology, but I have been playing with it on Lion and have been impressed by it so far.  While it is heavy and fairly thick, its active area fits the entire screen and as it is capacitive, multitouch drivers are available for windows (therefore should be possible for OS X).  This seems like the best solution and I feel lucky that I even found it, to be honest.

LCD enclosure

To fit it, however, I have to make the LCD enclosure itself smaller.

Show here is the LCDs enclosure.  There is a front and a back.  The LCD panel itself is quite thin and its control board actually extends outside the main enclosure.  Where it can interface with a JAE cable.

Side profile of LCD panel

Oblique Angle

 Most of the space is actually taken up by the backlight mechanism.
To be continued....

The Elusive All-In-One

Let me introduce you to my new favorite form factor: The Embedded Compact or ECX.  When I took this out of its box, even though I knew its dimensions, I was shocked at how small it was.  I do want to caution that everything with these boards is proprietary including its cables and proprietary = expensive.  So know what your getting yourself into.  I've seen these available in either Atom or most excitingly Mobile Core 2 Duo configurations as this one is.

For perspective I have included a picture with a metro card (credit card sized).  To demonstrate how small these boards are.  The have the same dimensions as a 3.5" drive, but they are also quite thin as the mobile processor fans are small and the ram inserts horizontally on the underside of the board.

In terms of features you can see the PCIe x 4 slot, a DVI/VGA/HDMI out.  However, there is actually an LVDS out as well inverter pins (yes the entire LCD conroller is embedded in this tiny motherboard).  So you could connect the LVDS cable and inverter directly to this motherboard without any additional hardware.  Now the question is can the native LVDS resolution drive the iMac's 20" screen? And does this solve the problem with the inverter for the 20" iMac - maybe?

The underside shows the RAM (4GB) in place (purchased separately) as well as a slot for a Compact Flash Card.  This I also find to be a fantastic addition.  I need all the space I can get and although I am not sure, I would be surprised is an embedded board was unable to boot from the compact flash memory. This could mean with a 64+gb card no need for a hard drive, no extra heat or power, and a much faster system.


Here is the 2.53 Ghz Core 2 Duo Mobile (Socket P Penryn Processor) and its very reasonably sized heat sink/fan.

This is the first board that I have felt makes an all-in-one doable.  I have never liked the idea of shoehorning a mini itx or mac mini into the base at an angle.  Plus I had extreme concerns about airflow.  I imagine this sitting above the dvd drive with the cpu fan around the same place as the iMacs original fan.  This board also allows incorporation of a dvd drive.  Although not necessary anymore, I always felt it was part of the iMac's charm.  In addition, if no other hardware is required that would leave the bottom for placement of a powerwave adapter (to use the original speakers) as well as extenders/ports to make the rear I/O look as original/professional as possible.  It does use a power brick, but I am certainly ok with that as no internal powersource = less heat.
Now I could find this board impossible to work with, it may not fit at the top of the base, it may require a hard drive.  I don't know, but keep this in mind the original iMac was an embedded compact motherboard, it only makes sense to use something along those lines.

I already know I can thread LVDS cables down the neck into the base with a replacement 20" LCD.  However, I could also try to splice the existing panel to DVI.  I'm not sure which way I'm going to go - but I am leaning towards LVDS (if the native resolution is compatible) as it is embedded onto the motherboard, thus will turn on/off with the motherboard etc.  For people interested in doing this, you will need extra LVDS cable.  The best place to get it is ebay.  I find cables used in flat screen tvs are usually longer and of more use.  Examples of LVDS cables from tvs are shown in the pic on the right.

The biggest problem I'm going to have is with that damn 20" inverter (I am not running high voltage cables through the neck again - too unsafe).  Unlike the 15 and 17" I have not been able to get it to work independently.  Although there are pins for the inverter on the motherboard, it is one short.  I believe there is some voltage difference involving orange and yellow that turns the inverter on.  I am hopeful that maybe by having an active dimmer hooked up that this may solve the problem.  Obviously using the native inverter with the motherboard would be option number 1.

Option 2 would be to locate some other aftermarket inverter that will work.  I have yet to find one that is "flat" enough to fit in the monitor casing, but I haven't looked for sometime.

Option 3 is something I have recently begun to play around with and that is led lighting.  I could try edge lighting the lcd glass, replacing the CCFLs with these superbright leds from environmental lights.  These work on a 12v dc line which can be supplied directly from the motherboard without need for an inverter.  This is a 6 foot roll.  They do come brighter however, this requires a 24v dc line.  If this is not bright enough, I may try led back lighting instead of edge lighting.

Option 4 is using the 17".  Although I'd prefer the 20", if getting the backlights to work on the 20" proves too difficult, I already know how to do so with the 17".  And would be quite happy with a fully all-in-one modernized 17" iMac G4.

I'd love to hear advice from people who have some know how with led backlights etc.  And as always I'd be happy to answer any questions.