Open45s: Display



#2

There seem to be a few options available for the display:

1. 2-line LCD

2. 4-line LCD

3. OLED

4. e-Ink

Of course, cost is going to govern which option we should hone in on, but what is the efficacy of the respective options?

To my mind 4-line LCD is a minimum. We want something enhanced from the current offerings, but not too expensive.

Edited: 4 Nov 2007, 2:25 p.m. after one or more responses were posted


#3

Two or possibly four line LCD. But 4 lines vertically, not 2x2.

#4

4 x 20 LCD modules are available in a 65mm x 28mm form factor, like this one

(no stock though)

I would put cost down the list, getting something that fits and works is the most important criteria. I'd rather have a physical working calculator with a $50 display than a hypothetical "dream" calculator that never gets made because you are still waiting on your dream $2 custom display.

OLED has the advantage of more compact form factors, at the expense of being full dot matrix which requires more effort to drive than a character module solution. The OLED character modules look to be too big, but there might be a smaller one out there.

The entire project hinges around what display is used.

Dave.


Edited: 4 Nov 2007, 4:21 p.m.

#5

I'd have thought that a 4 line display is going to give the expectation of graphing capabilities which nobody has said they want.

Character based displays typically cannot do graphics so adding graphics as a requirement would, as DaveJ has pointed out, significantly complicate the display driver.

So my vote would be for a two liner of some kind. OLED or LCD are both good. An LCD should have a back light that can be turned off.

- Pauli


#6

I am not sure that a 4-line display necessarily implies graphing. I would prefer a 4-line display without necessarily implementing graphing functions.

Quote:
I'd have thought that a 4 line display is going to give the expectation of graphing capabilities which nobody has said they want.


#7

Quote:
I am not sure that a 4-line display necessarily implies graphing. I would prefer a 4-line display without necessarily implementing graphing functions.

I agree. A 4 line LCD does not imply graphics, that is why I posted a link to a 4 line character based module. You can't do graphics on that.

4 lines gives a lot more options, especially given soft key menu operation. It means you can keep 1 line dedicated to the menu if needed.

Also, 20 characters per line is much more inviting than the more standard 16 characters.

Dave.


#8

I didn't say a big display implied graphics, it clearly doesn't. I said that it gave the expectation of graphics....


- Pauli

#9

I'd like to make a proposal (actually I made it above already, but this thread here is the right one):

Let the folks being most knowledgeable in displays look for the ones available on the market fitting into the dimensions of

  • a Pioneer
  • a Voyager
  • a 35s
  • a "landscape Pioneer" (as Dave proposed above)
and featuring enough dots to support 2.5 lines or more. Then we will have a more realistic base for our further progress. Please, go out and search. Looking forward to the responses,

Walter


#10

For the landscape format models the standard 118mm x 36mm LCD module is a good fit. 2 lines by 24 characters, very versatile. Claimed thicknesses from 8.8mm or so. Plenty of vendor choice, and low in cost.
Mouser

Example Datasheet

Not sure how many keys you can fit in after that though.

As previously mentioned, the 80mm x36mm module format would allow and interchangable LCD or OLED display, but only in a 16 character x 2 line display. But you could put keys to the side of the display.

The LCD modules have various pros and cons:

Pros:

- Easy software development

- Multiple sources

- Defined mounting dimensions and holes make case design potentially easier, especially by a third party.

- Low cost in one-off's and off-the-shelf

Cons:

- Greater power consumption than an LCD alone (typically a few mA @ 5V), but still low enough for say a year of typical operation from a AAA or Lithium coin cells.

- Not bit mapped, although you can often do custom characters

- Thickness may be an issue

- They are big


Given that a calc design is not about the display, but about the look and feel, and operation, yet you need a display to get the project off the ground, LCD modules do offer a reasonable compromise.

Dave.


Edited: 5 Nov 2007, 10:19 p.m.


#11

Quote:
Not sure how many keys you can fit in after that though.

In a voyager dimensioned case, you'd get 30 with the 118mm display and maybe 34 with the 80mm one. This assumes a small enter key so it is really 29 and 33 with a large one.

Not exactly ideal :-(


Pauli


#12

Quote:


In a voyager dimensioned case, you'd get 30 with the 118mm display and maybe 34 with the 80mm one. This assumes a small enter key so it is really 29 and 33 with a large one.

Not exactly ideal :-(


What about a landscape Pioneer?
You could squeeze at least two extra keys on the side of the display in that case.

A 24 character display is certainly an attractive prospect.

Dave.


#13

Check this out:
Varitronix

A 40x2 LCD in a tiny 108mm x 20mm x 12mm package - WOW!
That could allow an even shorter Voyager form factor.

I guess the only complaint would be the characters might be too small. But I think they are the same size as my uWatch, and I think that's just fine.

Imagine what you can do with a 40 character display though...
Might look a bit funny doing normal calculations, but would be awesome for a formula entry mode for example. Would certainly set the calc apart from anything else on the market.

Gotta find someone who sells it though.

Dave.

Edited: 5 Nov 2007, 11:21 p.m.


#14

Mouser seems to sell most of this product line.

They have the 20x2 (65mm x 20mm x 8mm) character version with LED back light for $13.61 in single quantity. I'll bet that they can get the 40x2 if you need it.


Edited: 6 Nov 2007, 12:16 a.m.


#15

Quote:
Mouser seems to sell most of this product line.

They have the 20x2 (65mm x 20mm x 8mm) character version with LED back light for $13.61 in single quantity. I'll bet that they can get the 40x2 if you need it.


Interesting, Varitronics don't seem to have the 20x2 20mm version listed as a product, yet Mouser have it in stock.

20x2 20mm

Maybe discontinued?

Otherwise the 20x2 20mm module is a very nice option indeed.

Dave.


#16

They only have four pieces in stock, no data sheet, and it is non-RoHS, so it seems likely that it is discontinued.

#17

Digikey have listed the Varitronix MDLS-20433-C-LV-G
A 20x4 module at 65mm x 28.4mm x 8mm

http://dkc3.digikey.com/PDF/T073/P2279.pdf

The Varitronix website has not heard of it though.

Could be used in either the Voyager or Pioneer. More suited to the Pioneer though.

4 lines would be awesome on the Pioneer. One row for soft keys, and 3 working rows.

Eric Smith should use this one in the DIY4!

Dave.


Edited: 6 Nov 2007, 4:19 a.m.


#18

Is there still interest in a landscape Pioneer, or are we aiming for a true Voyager if we go landscape? Whichever we use, shall we call our form factor the Phoenix?

I would dearly love to see a 4-line LCD!

Cheers.

Quote:
4 lines would be awesome on the Pioneer. One row for soft keys, and 3 working rows.

Eric Smith should use this one in the DIY4!



Edited: 6 Nov 2007, 6:08 a.m.


#19

Quote:
Is there still interest in a landscape Pioneer, or are we aiming for a true Voyager if we go landscape?

With both of the screens mentioned (40x2, and 20x2), a Voyager form factor is easily possible. In fact you could make it smaller in the horizontal, and you'd be pretty silly not to try I think. Smaller is better.

I would use the 40x2 display, it opens up so many possibilities.

Does someone want to try and photoshop up a Voyager with the 40x2 display?

No need for the landscape Pioneer.

Quote:
Whichever we use, shall we call our form factor the Phoenix?
I would dearly love to see a 4-line LCD!

4 line is easy on the Pioneer shape, and also possible on the Voyager as well.

Looks to be plenty of choice in LCD modules actually.

Phoenix is as good a name as any!

Dave.

Edited: 6 Nov 2007, 7:11 a.m. after one or more responses were posted


#20

PalG, over to you...


Quote:
Does someone want to try and photoshop up a Voyager with the 40x2 display?


Can we mock up both a 40x2 and a 40x4, please?


#21

Quote:
PalG, over to you...

Can we mock up both a 40x2 and a 40x4, please?


40x4 won't fit.

Just to consolidate the list, the ones suitable for the Voyager would be:

40x2 at 108mm x 20mm
24x2 at 100.1mm x 26.4mm
20x4 at 65mm x 28mm
20x2 at 65mm x 20mm

The 24 or 40 character ones are the pick. The shorter ones would look a bit funny I think.

The 20x4 is a sure bet for a Pioneer, but I haven't looked at alternatives for that form factor yet, been focusing on the Voyager.

The 40x2 display would put the design into the old pocket computer display category! The possibilities are quite exciting...

Dave.

#22

Well, suitable LCD modules are coming thick and fast now.
Powertip have a 24x2 module suitable for the Voyager.
The PC2402-H at 100.1mm x 26.4mm
Not as slim as the 40x2 module, but maybe a good option.
RS components stock the brand, but haven't checked for actual stock of that part yet.
Powertip list

Batron also have various 20x4 displays in the 65mm x 28mm x 8mm package, stocked by Farnell, with a choice of white or yellow background.

Optrex probably have something suitable too.

Plenty of choice for both the Voyager and Pioneer format, and I'm not even doing an exhaustive search.

I do hope Hugh's OpenRPN and Eric's DIY projects make use of these bigger displays. 16x2 just doesn't seem to cut the mustard any more.

Dave.

#23

Hi!

Quote:
3. OLED

To offer at least one suggestion for option three, how about one of those:

http://www.densitron.com/Displays/Displays.aspx?nCategoryID=10

The ones toward the end of the list seem most promising to me.

Greetings, Max


#24

Quote:
To offer at least one suggestion for option three, how about one of those:

http://www.densitron.com/Displays/Displays.aspx?nCategoryID=10

The ones toward the end of the list seem most promising to me.


It certainly doesn't look like the HPs from the good old times... ;-)

But I must say especially the last one in the list is VERY attractive and won me over. My vote for it!


#25

Hello!

Quote:
It certainly doesn't look like the HPs from the good old times... ;-)

If you only think about calculators, maybe. But I had the luck to work with HP laboratory equipment (for microwave imaging) during some years in the early nineties and I remember some displays, although being made of silicon (instead of polymer) LED matrices, looked not too different from that.

Greetings, Max

#26

The last one looks very promising indeed. Resolution of 256 x 64, so this would allow for 6 lines of more than 40 characters each. It comes within a module size of 88mm x 28mm, featuring a visible area of 78.8mm x 21.2mm. On our Voyager it would leave space for 36 keys...

Is there anything comparable in the LCD world?

Edited: 6 Nov 2007, 1:51 p.m.


#27

Quote:
The last one looks very promising indeed. Resolution of 256 x 64, so this would allow for 6 lines of more than 40 characters each. It comes within a module size of 88mm x 28mm, featuring a visible area of 78.8mm x 21.2mm. On our Voyager it would leave space for 36 keys...

Is there anything comparable in the LCD world?


That produces light output and draws at least 0.2W of power for 50% display? then the answer is no.

BTW, those who want the datasheet without having to register, HERE IT IS.

It's very nice, but the battery solution is problematic, your software complexity has just gone up several orders of magnitude (the driver chip does not do the fonts for you), and people will want graphics and will fuss over the fonts and their size until the cows come home.

Dave.


#28

I realize I'm coming very late to this discussion, but what's wrong with the display on the 28S? Unless you're doing a graphing calc, or displaying equations in a book form, why add all this cost, complexity, and power draw? (plus, I once broke the display on my 48sx, it's a very large and fragile surface area)


#29

Quote:
I realize I'm coming very late to this discussion, but what's wrong with the display on the 28S?

It's a custom graphic dot matrix, so is in no way suitable.

Quote:
Unless you're doing a graphing calc, or displaying equations in a book form, why add all this cost, complexity, and power draw? (plus, I once broke the display on my 48sx, it's a very large and fragile surface area)

No one is talking about practically using the screen from a 48/49/50.
But those points are precisely why I am recommending going for an off-the-shelf character LCD module.
Everything is going to be a compromise, so you may as well choose a compromise that eases your development effort.

Dave.


#30

I'm coming to this topic late too (and I have not read the entire thread), but I will comment that every time this kind of thing comes up, a lot of people get all excited about OLED. Just forget about it! Those things are power hogs and are not at all suitable for calculators. Dave's recommendation for an off-the-shelf LCD is a very good one. They are made by lots of companies, and if for some reason your supplier goes belly-up, there are plenty of drop-in replacements available immediately from other companies and with no tooling charge. I have used several of the intelligent character LCD modules, and they're pretty easy softwarewise, and they mostly use the same instruction set so going from one brand to another does not require re-writing the software. So far I have not used the graphics ones, but I understand they mostly use one of only a couple of chip sets.

#31

Quote:
Quote:
Is there anything comparable in the LCD world?
That produces light output and draws at least 0.2W of power for 50% display? then the answer is no.

:)) OK, but you know what I was asking, don't you? Please remember the objective as written above:
Quote:
...look for (displays) available on the market fitting into the dimensions of ...
  • a Voyager
  • ...
and featuring enough dots to support 2.5 lines or more.
So far only one display in our list meets this objective. There must be more!

#32

Quote:
So far only one display in our list meets this objective. There must be more!

Why 2.5 lines?
I assume it's because you want something for the soft menus or annunciators?
Two character based lines is more than enough for a calculator.

Saying that a two line character display is not suitable because it does not fit some arbitrary "2.5 line" requirement seems overly restrictive and a bit pointless.

A 2x24 or 2x40 line LCD display would provide a lot of flexibility, with all sorts of various menu and annunciator systems being possible in software.
Both are only 20mm high and almost perfect for a Voyager form factor.

Also, to get "2.5 lines" you either need a full dot-matrix graphic display, or a 4 line display. Both of those solutions have problems.
Although the 4 line display module is not an entirely bad option.

Dave.


#33

Quote:
Why 2.5 lines? I assume it's because you want something for the soft menus or annunciators? Two character based lines is more than enough for a calculator.

This would allow for displaying a soft menu for a longer time, until you select another menu or drop it explicitely. And you'll still have 2 lines for output of results. Please see an example here. IMHO a permanent menu line would add a considerable benefit to a calculator.

BTW, that's why I left yellow shift "unused" at the top left 8 keys: E.g. press top left key to execute SINH while f SQRT lets you execute SQRT - so TOP.FCN became dispensable.

Nevertheless, I'll try with 2x40 line LCD.


Edited: 7 Nov 2007, 12:35 a.m.


#34

Quote:
This would allow for displaying a soft menu for a longer time, until you select another menu or drop it explicitely. And you'll still have 2 lines for output of results. Please see an example here. IMHO a permanent menu line would add a considerable benefit to a calculator.

No doubting that, more lines is better, but a 2 line display is still very capable, and there is absolutely no reason to exclude it.
There are three choices here:
1) A 2 line display module (great for a Voyager format)
2) A 4 line display module (less than ideal for a voyager form factor, more suited to a Pioneer)
3) A full dot matrix display that allows "2.5" or 3 lines. This has all sorts of issues as stated before. And no one has thus far presented a suitable low power LCD version. But I'm sure one is out there if someone cares to look.

You've gotta work with the components you can get in order to get a project off the ground.

Quote:
Nevertheless, I'll try with 2x40 line LCD.

No need to try, it's guaranteed do-able, it's just how you decide to go about it. There are plenty of ways to implement limitless functionality into a 2 line display (think 42S, 33S, 35S, my uWatch etc)

Dave.


#35

When working with the 35s I keep wishing that I could just have more information at a glance rather than having to R v all the time. If we go with the standard x,y,z,t stack then having a 4 line display would in my mind be very desirable.

Cheers.


#36

Quote:
When working with the 35s I keep wishing that I could just have more information at a glance rather than having to R v all the time. If we go with the standard x,y,z,t stack then having a 4 line display would in my mind be very desirable.
Cheers.

A display mode could show 4 stack levels simultaneously,
two per line. With a 40-character, 2-line display, there's
enough room.

Don't know if it's easy to do, but another display mode could
use the whole display to show just X in double-width, double-height
characters, so I could use the calculator without reading
glasses.

Paul Guertin


#37

Quote:
Don't know if it's easy to do, but another display mode could
use the whole display to show just X in double-width, double-height
characters, so I could use the calculator without reading
glasses.

That's not possible with the character based modules I'm afraid, one of their down-sides.
Full dot-matrix would be needed for that.

Dave.

#38

A 4x16 display at 72mm x 48mm, Everbouquet brand.

Farnell Stock

Dave.


#39

Having a look at this site, there seems to be some more options for displays:


[link:http://www.gy-lcd.cn/readarticle/htm/class/C81_1.html]GY-LCD Mfg[/link]

Do we want to specify trans-reflective with back-lighting to our spec?

Cheers.

My, that PCM 4002A-FL-YBS looks nice (for a 2-liner)...


#40

Quote:
Having a look at this site, there seems to be some more options for displays:

GY-LCD Mfg

Do we want to specify trans-reflective with back-lighting to our spec?

Cheers.

My, that PCM 4002A-FL-YBS looks nice (for a 2-liner)...


That one is 33.5mm in height, compared with 20mm for the Varitronix unit. I believe that does not leave enough key space.
BTW, many manufacturers do the same size 40x2 display, but only one does the 20mm version that I can find.

BTW, backlighting (LED) on these displays is usually quite poor. I probably wouldn't bother. No calculator I own has a backlight and I've never needed one. I added one to my uWatch because I could, and it's used as watch so should have one, but it's very ordinary indeed.

Dave.


Edited: 10 Nov 2007, 7:12 a.m.


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