Sunday, 26 June 2016

How to build yourself a "Cintq" - Part two: LCD and monitors

Before going on, let me re-state that I think that the best choice of Intuos to make a build is the Intuos 3.

They already have a spatial resolution of 5080 lpi (against the 2540 of the precedent series), the model has hotkeys - which means that their driver shows a change screen function associated to a button, which is something very useful that I still have found no way to emulate with my Intuos 2,
Intuos 3 A3, PTZ-1231, 12x19"
Outside my usual budget, really.
there are still some years before the driver support is discontinued in Mac and Windows and, finally, they still do not cost as much as their more recent brethren.

And the active area of biggest one, the 12x19" PTZ-1231, can cover both a 22" screen (16:10) and a 21.5" (16:9) with some mm to spare, whereas the predecessors leave out about 2/3 of an inch of screen, width-wise. 

The Intuos 1 & 2 are way more cheaper, of course... it can be a battle, to get them up and running in modern OSes, though; It is the main reason that they are cheaper; Also, finding accessories - like the pens - for these older machines is going to become more difficult.   I like battles and don't have a dime, so I decided to "standardize" myself on the Intuos 2... but that is another issue.

Now, let's say that you already have an Intuos tablet (or a Monoprice , or whatever - as long as their drivers allow screen mapping and tweaking of the tablet area, a tentative can be made) and have decided to take the step of placing a screen over it...

Which screen? Or, better, which LCD panel?

Again, you should peruse the Bongofish forum, looking for someone who used your tablet and managed to get it to work well.

If you find a "recipe" that works for you, you do not really  need more.

Alternatively, you can arm yourself with some basic notions on LCDs, check Bernard (bongofish administrator) glorious Simtiq Planner,  look for a panel on a LCD database like,  and try a new LCD-tablet combination.

If you do, be fair to all, and report how it went in the forum, so that others may avoid your mistakes or share your triumph. 

What to look for, if you do not find a "recipe" (LCD-Tablet and how to assemble information) that suits your tasks?

I cannot really tell you, because it is a question of desires, budget, constraints etc...

When you go for this you are, in fact, deciding to embark in a bit of experimental design...

What I can give is some fundamental notions to orient your choices.

First of all, no LCD is really designed with the aim of letting pass, through it, the signal from the pen (though, some actually manage to do so, almost  by accident).

Almost invariably, they will need to be modified.

In the best case scenario, this means just removing its metal frame (then, optionally, carving up the parts of it that enters into the active area, and placing it back - if the LCD has a "single plane" structure, like a LG LP116WH2, for example, it is all that it is needed to prep it, really).
LG LP125WH2, 1366x768, IPS, LED
The panel "Timing control" board is on the same plane as the LCD panel, below it in the photo...

The back of the frame is in the way of the pen around the borders, but, once removed the tape that covers- protect the board, unscrewed the board and unzipped the small flexible pcb that connects the board to the LED strip, it is relatively easy to remove the back of the frame and cut out the parts that come in the way, and place it back, to have a final assembly as ... beware, because the the LED strip may be stuck to the frame and is easily damaged.
THe LCD proper is a sealed sub-unit insidethe frame so, if you are careful, it is easy to preserve its integrity and prevent any speckle of dust from entering it. 

LCD panels doesn't get any easier than this, to be prepped for use in one of these machines.   

If you have an Intuos 3 A5 oversize (6"x11"), this panel is most probably the best fit for it - size-wise, it is almost the exactly the same aspect ratio and just 12[horizontal] aand 16[vertical] pixels smaller than that tablet's active it has no metal apart the external frame and is just a some 3 mm thick, it is easy to see if the pairing works - just connect it to a controller, switch it on and place it on the tablet. If you see occasional false clicks, don't worry - usually those are "cured" grounding together the digitizer metal back-plane and the LCD. The resolution is not stellar but, at 12.5 inches, it is enough for most uses.

In the worst case scenarios, this means assembling LCDs out of spare parts from two or more screens... and even build some new parts (a C.N.C.-milled back-case with a LED-holder area, springs to my mind).

In any case, the rate of failure is far from negligible (with an 80% success rate to date, I am a lucky -or just quite cautious - bastard, for example). 

So, if you can lay your hand on a used LCD versus a new one, it may be a good idea (unless you plan on devolving the destroyed monitor, or LCD, to its vendor saying that "it mysteriously stopped working" - that's fraud, I do not condone it, and it won't fly if it's a naked panel, anyway; it can work with a whole monitor and a selling store that doesn't care too much about investigating claims).

However, bear in mind that a used LCD had a life, and it may arrive from someone that already dismantled it, trying to make his own project, and placed it back together in some more or less correct way (happened to me, once, with a LCD panel).

Also, there is no way to know when you may find a 2nd hand LCD panel or monitor of the type that you chose... next week I should receive a LG IPS 224; it took me a year'to find one within my budget.

So, 2nd hand -> less monetary risk, more time spent chasing it down. It all depends on how you value your time.

Also, one may hunt LCD Panels - pro, you can find documentation online, like spreadsheet and photos, on the panel itself that goes beyond the simple specs in in the marketing page of the producer... cons, you must find the right ancillaries for the panel  - 

or look for complete monitors - pro: all the auxiliaries pieces needed are shipped with it; cons: the packaging may not be the better suited for the task, for example most monitor  with CCFL lamps that doesn't use a separated power unit have one that integrates the back-light's driver, which constrains the design. Also, there is almost no way to know what LCD Panel is inside a given monitor so, it becomes a bit of a stroke of luck to get one that is worth a try.

The glorious Dell 1503fp,
the first monitor to be Cintiqized by Drew Northcott, he who created the bongofish forum

It is a now old monitor, that you can find in ebay for some 30 bucks; it reportedly does not produce interference with the working of the Intuos (1) 9x12 or 12x12 even in its native form, and is not the worst twisted nematics, CCFL monitor around.

As many monitors that use a power brick, it has a small CCFL inverter, which may make relatively easy to replace the original CCFLs with A LED setup. In fact, this image comes from a  tutorial on it..
OK, I hope that they will add back the now missing photos, some day.

Again, there is no "best choice"...  of my three machines, the one that works better has only the screen ancillaries new, the tablet was 15 years old and the LCD was out of the wreck of an Arnova g20 and rudely dismantled - by its previous owner - trying to build a projector.

The one that I use the most is based on a then "unknown" HP monitor, with CCFL lamps, a back-light driver in the power unit and as thick as practically acceptable... on paper, almost the last LCD panel to choose, for assembling on of these contraptions - I bought it as a second hand whole monitor, so... surprise; I still managed to get it to work quite well.

On the other hand, I find unusable- screen's too dim and bad colors - the first one that I made, a new LCD on a Wacom Store "demo" unit that had hardly came out of the box in the shop where it was originally displayed. It was based on a known "recipe", and it costed me like the other two together. But the screen is just too crappy anyway (I have grown older and my sight didn't improve with age).

OK, no more digression, let's go on.

When you look at LCD panels , you'll see that they use one of three main technologies, for the proper LCD part

Twisted Nematics, TN - the first type of LCDs to appear on the market. Fast response time, low viewing angles and, associated to this, unreliable colors - the shade you see changes just moving one's head. If possible, to be avoided... fast response times may appeal to gamers, but have no sense in a drawing machine, when the PC may take entire seconds to complete a line (using the Photoshop smoother at 300 pixels, to mesh a 500pixel  long area... one stroke, going to the coffee machine, pouring a cappuccino, and maybe the computer has finished the stroke, by the time I come back to make a second one). On the other hand, you can get a used 15" monitor of these for some 30 euros, and so build a usable "Cintiq" with less than 100 bucks...

In Plane Switching , IPS - somewhat slower, in the first iterations came with reduced contrast values but have much improved over time,  almost perfect viewing angles and color stability - little color fading moving around the screen.. PLS is, virtually, the same technology as marketed by Samsung. A significant drawback is that its introduction is recent, and most LCD panels using this technology have a 16:9 aspect ratio that does not correspond to that of any of the Intuos, (apart the LCDs created for Apple products: IPAD are 4:3 and MacBooks are 4:3 or 16:10).

Vertical Alignment, VA - Great viewing angles and colors, horrible response time (usually not inferior to 30 ms). Given the long response time, rarely used on the home monitors market, but mostly for industrial ($$) or medical ($$$$$$) use,  which may be one reason why they are produced in a wider range of aspect ratios than IPSes.
It is usually preferable to pay top money for a new LCD panel of the same size and shape than re-designing an industrial machine - or a medical unit - to accommodate a newer, mass market LCD.

As far as this kind of projects go, VA and IPS are both valid. TN ... unless they are very good value for the money, are better left to gamer.

Beyond the type of the LCD technology, also the type of backlight source has its importance.

Essentially, there are two types:

Cold Cathode Fluorescent Light, CCFL - (where "cold" is actually some hundred degrees) is the oldest technology, essentially the CCFL are small "neon" bars. They work with a voltage that goes from 1300 at start-up to some 600 volts during normal operation, voltage which is provided by a step-up inverter with the start-up reactances integrated. If said inverter is separated from the power unit, it is almost) simple to replace the CCFLs with LED strips and their driver unit (essentially, it is a bolt-on substitution). If it is separated, it requires a bit of reverse engineering to locate the actual power and signal lines (the replacement kits usually requires a ground line, a +12 volts power line, a on/off and line and and adj/dim line). The CCFL high voltages make them a notable source of interference, and the transformer inside their inverters is even more of a noise source... in my machines, I managed to place them as far from the digitizer as it was possible.
Panels with CCFL lights designed for office use are meant to be opened up to replace the CCFLs, when they reach the end of their life (around 12-18 thousand hours, i.e 4-6 years in office life, two years in 24/7 uses).

This make modifying them, to be placed over the digitizer, relatively easy.

Also, to simplify their substitution, the CCFL use standard connectors and already made extenders are easy to come by.

If one need a longer extension, it is feasible to take one of said extenders, cut (better not at the center, on one cable , toward one extreme, on the other, toward another ), splice and solder additional cable to extend it further, if possible of the same gauge and class (OK, I did it with 220V house wire, adding a huge and thick insulating  coat to one of the two, to reduce capacitive coupling -  it shouldn't, but it works well anyway... just luck, probably)

LED lights - they operate with voltages that reach, at maximum, some 60 volts and as such, a part particularly unlucky cases in which the Pulsed Width Modulation  used to dim their brightness directly resonate with some of the digitizer specific frequencies, the interference produced  by this light source tend to be much more subdued than those produced by CCFL lamps and often fall below the threshold of noise that the digitizers are natively able to filter out.
On the back side, the LED estimated life is usually on par with that of the liquid crystals and, as such, these displays are not meant to be opened, ever.
 Their design doesn't necessarily accommodate our needs to manhandle them.

Also, many panels with LED backlight have the LED driving circuits inside the controlling board on their top (yes, the one that, unless the panel has a "single plane" structure - with the board already  lying below the panel - usually needs to be folded out of the way) and small flat flexible PCBs, with multiple lanes, connecting the actual led strips to the board.
Depending on the design of this, and one's accessibility to the right pieces (essentially, ZIF-toZIF adapters and FCC of the same pitch as the connector) these lanes can be very easy to extend, or instead be virtually impossible to tame.

(My smallest machine was built out of the wreckage of a precedent try... I had modified the LCD with no issues, but couldn't find the FCC or the ZIF-to-ZIF to extends its led connection once the board was folded out, so in a fit of impatience I destroyed the LED strip connection lane trying to solder electric motor wire to it; a couple of years after, Nyjtouch sells the FCC, zif-to-zif extenders and I find a 2nd hand LCD of the same type... in a couple of  hours or so, it was done)

A note: many modern LED backlight TV have a zoned backlight setups, with the LEDs dispersed in the middle of the active area that can be individually dimmed.
IT may help getting better contrast ratios, but this means that they have these LED power lanes in the middle of the pen signal path. Not sure about it, but I'd avoid them, if possible. 

Desktop LCD monitors have, almost always, at least 8 bits of resolution per each color   -billion of colors. the fabled 16.4 million colors. Some high end monitors have 10 bits per color channel, and can display a billion colors.

Many laptop Screens only have 6 bits per channel color resolution, and can thus display only 64 gradation of gray, or 262 thousand colors (now you know why, when drawing gray-scale images on your laptop, you never seem to be able to pick the right, intermediate value that you need -  the computer and graphic adapter are trying to give it to you, but that's the screen that simply cannot show it).

Smart LCD controllers try - and nearly succeed - to close the gap, using spatial-temporal dithering techniques (for example, flipping a pixel's color between two levels or, similar to what the JPEG does, considering a 2x2 pixel cell as base color unit, and using the combinations to dither, or both the techniques at once), which can close the gap with 8 bits panels.

So, 6bits/8 bits has its importance, but it is not fundamental (note: I hardly ever use color anyway, so take this with a grain of salt... also, the LCD controller you is going to be only as smart as it is, not as smart as its best competitor is).     

Unless you made an incredible bargain (I saw an Intuo4 XL going for 140 euros, this week... I still want to cry, I paid my Intuos 2 180! ) or it is a UC-Logic (currently, the only other maker of digitizers that is worth a try...), usually the square inch of your tablet has costed you a lot more than the square inch of screen, which will prompt some soul searching, when it comes at choosing sizes, as your digitizer and the LCD may have a different aspect ratio.

 As I noted, most IPS panels with LED backlight comes with a 16:9 aspect ratio. Though replacing the CCFL with LED kits is possible, it is not necessarily easy or something you may want to risk.

So, choosing a LCD that falls all inside the active area, is IPS and has led backlight may mean to forego half of the tablet, as almost inevitably one such panel is a "modern" 16:9....

Though it is true that it is simpler to calibrate a machine when the LCD image falls all inside the digitizer's active area (my last), in my experience it is also quite simple to tune machines whose screen is bigger than the digitizer in all directions (my first) and only slightly more annoying to tune one where the screen is wider but the digitizer is taller than the LCD (my biggest -  first one tunes the screen width, then the tablet height).

In reality, a smaller LCD makes easy to move the screen position around the desktop... which doesn't really matter, on the biggest builds;One cannot shove around his main monitor in the desktops space, anyway.

Now the main trick, to live with a screen  that is wider than your tablet, is to make sure that you can still always reach the scrolling bars of the programs.

Not being able to scroll with the pen is, in my experience, the most conspicuous font of frustration in such a set-up.

There is a program called Power Strip, from a Taiwan Enterprise called Emtech, that allows one to "carve up" custom-resolutions (essentially, adding black bands on the screen) out of the screen. As it also allows to finely tune the internal timings of the LCD, which can reduce substantially the interference faced by the digitizer, and it comes shareware with a month of access to its full features, it is usually worth a try. If with it you can tune out some (or all) of the pen jitter AND reduce the screen used by the OS just to the tablet area, its 40$ lifetime license is money well spent.

Alternatively, a work-around can be to place the task-bar on the right, and extend it till the programs right borders falls inside the active area (it is what I did with UBiQ in Windows rustratingly enough, Ubuntu is idiotic enought that it thinks to know where I need to place the).

Then, placing a setting for Explorer.exe, in the tablet driver,  that allows access to the whole screen area, makes so that even the icons in the tray area can be reached...and one can almost forget that the pen doesn't reach every corner of the screen.

If the LCD is bigger on all sides, but the difference is smaller than the smaller icon in use ( 15.4" in 16:10 is about six mm wider and taller than an Intuos 4 large... if well centered, the digitizer active area falls - at 1440x900 - 10-pixels from each border; icon sizes usually start at 16x16... any Icon on sight is reachable), it is hard to remember that it is bigger at all.

So, resuming all of these, the ideal screen is

Using IPS (or VA)  technology

With a good resolution (but, if it is a small machine that is not going to be used as  the main screen, it may not be wise to obsess over it - better a nice screen with a lower resolution, than a crappy one with an higher resolution)

Possibly, with 8 bits per color channel (again, if the LCD controller before it is good, a 6 bit panel may look just fine enough)
Using LED back-light (possibly, with either an external LED driver, or with a typology of board-LED connection that you already know how to extend)

With only one circuit board, or having a "single plane" architecture (If the circuit boards are already out of the way, it doesn't matter too much)

Of a size and format that cover as much as possible of the digitizer, with a minimum of LCD overhangs...

Ok... next time, I'll try make a small list of the combinations that I know to work.

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Feel free to point me out conceptual, orthographical, grammatical, syntactical or usage's errors, as well as anything else