I thought I'd start a new thread on this design. So those who don't want to talk about credit card calc design, please ignore.

Two basic design options are presenting themselves:

1) Less powerful design (say PIC18) with high contrast 8 digit 14 segment LCD display window 45mm x 8mm. Thickness can be no less than 4mm.

2) More powerful design (say PIC24 or PIC32) with lower contrast 35mm x 9mm 128x32 dot matrix display window. This would allow 4 lines of 16 characters with an 8x8 font. Bigger fronts are of course possible to compensate for the lower contrast. This is the same display as for the uWatch MK2. Thickness can be no less than 3mm. More expensive by at least $10 in parts cost.

Both designs would be standard credit card dimensions, entirely solar powered (need to get samples and test, but looks possible), possibly have super cap power backup, a standard ICSP programming header on the edge, and a Micro SD card is also possible. And other edge mounted stuff is also possible, like a rocker switch, IR LED etc.

Micro USB connector is only possible on the 4mm 14sgement LCD design.

I see backlight as being pointless on both.

Either design could of course have a powerful processor and Micro SD card etc, but I think all that power is kinda pointless on the limited 8 digit 14segment display design.

Either design can have either a membrane overlay or capacitive touch sense keypad. As many keys as can fit.

The membrane option adds some thickness due to the material and the domes (say 0.5mm minimum), but is possibly much cheaper once NRE is taken out, and people could in theory design their own own to have whatever key overlay they like (it just sticks on the panel).

The cap touch sense is the thinnest option, and no NRE for the overlay. But it does use more power (likely not an issue), and would not have any tactile or key "feel". A flat stick-on adhesive graphic overlay would be an option, allowing users to add their own stick-on custom overlay.

So, a few questions:

1) Who would buy such a thing? (cost say $60-70 approx)

2) What display/thickness option and why?

My initial thought is that thickness should be the main criteria, as much as I love high contrast 7 segment displays. So the more expensive 128x32 dot matrix and cap touch panel seems the best option.

Case is entirely resin fibreglass with a choice of funky colours top/bottom.

I've got all the parts bar the solar cell and am getting rather excited! :->

Discussion please...

Dave.

Edited: 14 Nov 2009, 6:31 p.m.

What is the thickness (3mm or 4mm) you are describing? Surely not the thickness of the entire watch?

I'd buy either one, but I think I'd rather have the dot matrix display and more powerful processor. On the other hand, I do also want the USB interface. Why can't the micro-USB connector be put on the dot matrix version? If that would make it slightly larger (in any dimension), I think I'd still want it.

I'm sure I'm in the minority here, but I'd much prefer the higher contrast larger digit display. I don't really want to play chess on a calculator just calculate (and maybe program) so all those pixels and higher speed aren't needed. Besides

Quote:

---

35mm x 9mm 128x32

---

means each pixel is roughly 270um square (40% smaller than the uWatch LCD) you're going to need a magnifying glass -- if not a microscope -- to play chess on this display.

4mm would make it about one half the thickness of the humble HP 6S solar -- which I think is the thinnest "HP labeled" calculator ever made. Not to mention the only solar powered one.

$60 would be a great price for this!

I'd buy either. Probably more than one.

I'm in a real bind over which I'd prefer. I view a credit card sized calculator as being something to carry around for spur of the moment calculations. It needs to be thin to fit comfortably into wallets etc. It will also need a decent display because these calculations get done in all manner of places & I like segmented displays. The more I think about this point the more I'm leaning towards the thinner with dot matrix display -- an eight digit display is pretty small after all. Still I like contrast.

Either CPU would be fine. I'm not going to be playing chess on it :-) Although it could be the first solar powered chess computer to my knowledge.

Much as I'd like a thinner keyboard, tactile response is more important to me. The power use is moot since there is no battery and the solar panel is adequate. However, I'm not super fussed over this point -- i.e. either is good.

I don't see a huge need for USB connectivity if a micro SD card is present. Without the card, then USB becomes important. So put in a micro SD card.

And RPN only ;-)

- Pauli

Dave;
*The 14 segment high contrast/larger display, dome keyboard, thicker but with usb for updates is my choice but i'm just buying it - you're the one building it.

*I'd never want to put this in my wallet and sit on it. If it turns out to be possible; could you provide it with a lanyard hole for attachment to a key ring, a surveyor's vest, or necklace (RPN BLING!)?
*The price is ok as is the color choice. Put me in for a tie died one.

What I've always wanted is a credit card-sized RPN basic scientific calculator (no programmibility, no I/O). Something like that - except for the awful layout:

Solar-powered and high-contrast 7-segment display, as thin as possible.

But with this design, there is no space for the solar cell :-(
I also think there are too many keys for fat fingers to press.

BTW, the segmented display is 8 digits total & you're showing a ten digit number.

I think I've fully convinced myself that the dot matrix is the only way to go. I really don't think 8 digits is enough. Sign, two exponent digits and an exponent sign leaves four digits for the mantissa :-(

- Pauli

Quote:

---

2) More powerful design (say PIC24 or PIC32) with lower contrast 35mm x 9mm 128x32 dot matrix display window. This would allow 4 lines of 16 characters with an 8x8 font. Bigger fronts are of course possible to compensate for the lower contrast. This is the same display as for the uWatch MK2. Thickness can be no less than 3mm. More expensive by at least $10 in parts cost.

---

However...

If the layout is going to be a mini Voyager, well then #1.

Quote:

---

1) Who would buy such a thing? (cost say $60-70 approx)

---

Edited: 15 Nov 2009, 12:10 a.m.

I'd be interested in whichever model offers the thinnest design.

Quote:

---

What is the thickness (3mm or 4mm) you are describing? Surely not the thickness of the entire watch?

---

Yes, it's the thickness of the entire calculator, no protruding bits.
It's not a calc watch, it's a credit card calculator, two different projects.

[quote]
I'd buy either one, but I think I'd rather have the dot matrix display and more powerful processor. On the other hand, I do also want the USB interface. Why can't the micro-USB connector be put on the dot matrix version? If that would make it slightly larger (in any dimension), I think I'd still want it.
/quote]

The Micro USB connector could be added to the 3mm dot matrix version, but it would require a rather ugly cut-out, and not sandwiched neatly between the top and bottom panels.

The dot matrix version could of course be thicker to accommodate just the USB connector. But given that this is a credit card calc, you have to weight up the trade-off.

Dave.

Quote:

---

I'm in a real bind over which I'd prefer. I view a credit card sized calculator as being something to carry around for spur of the moment calculations. It needs to be thin to fit comfortably into wallets etc. It will also need a decent display because these calculations get done in all manner of places & I like segmented displays. The more I think about this point the more I'm leaning towards the thinner with dot matrix display -- an eight digit display is pretty small after all. Still I like contrast.

---

The dot matrix display can of course be turned into a large readable 8 digit display, it's a just a firmware thing.

The full 4 lines by 16 characters will be incredibly small, I've a got prototype running and you really have to concentrate to see it.

Quote:

---

I don't see a huge need for USB connectivity if a micro SD card is present. Without the card, then USB becomes important. So put in a micro SD card.

---

The USB is useful for firmware updates. Without a USB port, the user has to have a PICkit programmer to change the firmware.

You could you could have a Micro SD bootloader to do firmware updates from the SD card without the USB port, but I don't think Microchip provide such a thing, so it would have to be written.

Apart from firmware upgrade, I agree, I don't see the point is you have a Micro SD card.

Quote:

---

And RPN only ;-)

---

Not in any calc I design, I ain't no RPN fanboy, so you get selectable!

But of course it's open source, so do as you please :)

Dave.

Quote:

---

#2 would be more interesting and offer more flexibility. e.g. multiline stack, easier to program, etc... #1 is just an RPN version of many existing credit card calcs. I guess we all have different needs. I have a calc on my phone (many of them). I'm looking for a gadget--something to repurpose.

---

That might just be the most important aspect.

If it's going to be popular with people of all sorts, then I think it needs to be more versatile than a 8 digit display. Something people might want to repurpose. Otherwise it's just going to be yet another credit card calculator (albeit the worlds first(?) scientific one). I think it does need to be "gadget" like.

If I was designing it just for myself, then I don't care about programmability and gadget factor, so I'd want just want a high contrast display and scientific functionality.

Dave.

Quote:

---

If it turns out to be possible; could you provide it with a lanyard hole for attachment to a key ring, a surveyor's vest, or necklace (RPN BLING!)

---

That's easy, consider it done!

Dave.

Quote:

---

means each pixel is roughly 270um square (40% smaller than the uWatch LCD) you're going to need a magnifying glass -- if not a microscope -- to play chess on this display.

---

I've found another option, a 44mm x 12mm display window that has a 16 character x 2 line character based only display. Just like the uWatch, but only bigger. It is also only 2mm thick, so the 3mm calc is possible with this option.

Dave.

Edited: 15 Nov 2009, 3:41 a.m.

Quote:

---

Not in any calc I design, I ain't no RPN fanboy, so you get selectable!

---

Heathen! Just wait for the revolution ... you'll be lined up against the wall ...

Funnily enough when I started high school, the students were separated based on the language they had decided to study. Needless to say the teacher in charge of things said: "All those studying Russian line up against the wall". Much merriment and mirth followed :-)

- Pauli

First dreary eyed rough draft of what the uCalc will look like before I head to bed and actually think about it...

This is with the bigger 16x2 line character based LCD.

No thought what so ever put into shift functions or menu/program stuff yet.

Picture this credit card size and 3mm thick.

Dave.

Edited: 15 Nov 2009, 7:33 a.m.

Lovely!

- Pauli

Quote:

---

But with this design, there is no space for the solar cell :-(

---

This comes from my own RPN calculator, written in Delphi (don't need it anymore, as nice emulators/simulators became available). Of course, on the real thing the display need not be that wide.

Quote:

---

BTW, the segmented display is 8 digits total & you're showing a ten digit number.

---

I was thinking of a display capable of showing numbers like

-1.234567890x10-34

the _x10 annunciator and exponent digits being lit when needed. I am not sure whether such display is commercially available though.
BTW, the 10-digit number I showed previously was carefully chosen: when divided by pi it is a near integer and each two-digit group is the number of a fine HP calculator, the HP-01 watch in the center :-)

Regards,

Gerson.

Edited: 15 Nov 2009, 9:49 a.m.

Not bad considering it is a first draft. However, I think the hardware designer and the industrial designer should NOT be the same person :-)
I would certainly buy one, better if it cost under US$ 50.00 (so that I don't have to pay an infamous 60% import tax...)
I am quite sure there is a market for a credit card-sized RPN calculator.

Looking forward to the real product.

Gerson.

It looks great, but please, please make the STO and RCL separate buttons. This was a big mistake on the 20b, IMHO.

Can you shift the numbers over one position. Place the basic operations vertically. Put ENTER vertically between the numbers and the sci funcs. Put X<>Y and +/- above the ENTER.

Please?

I like the old school typewriter looking keyboard.

Rather than adding a micro-USB connector, just put four conductive pads at one corner, and route out a slot, so that the corner of the calculator plugs into a USB connector (on a USB extension cable) directly. Some thin "USB key" flash memory devices work this way. 3-4mm may be too thin, though.

Sure seller... reproduce the key layout of the 15c or 16c, call it the 15dj or 16dj.

Hello Dave,

A credit-card RPN calculator is a good idea. I'd buy one.

The current prototype picture seems to be missing a y^x key, unless I'm mistaken.

Quote:

---

Sure seller... reproduce the key layout of the 15c or 16c, call it the 15dj or 16dj.

---

Quote:

---

Rather than adding a micro-USB connector, just put four conductive pads at one corner, and route out a slot, so that the corner of the calculator plugs into a USB connector (on a USB extension cable) directly. Some thin "USB key" flash memory devices work this way. 3-4mm may be too thin, though.

---

Ah, neat idea!

Dave.

Quote:

---

Can you shift the numbers over one position. Place the basic operations vertically. Put ENTER vertically between the numbers and the sci funcs. Put X<>Y and +/- above the ENTER.
Please?

---

Oh, you mean something like this:

*rolling eyes*

I guess that's what I get when I show this on a HP forum!

The good thing about a touch panel design is if you don't like what's on offer you can put a new sticky front label over it, with silver highlights and everything!

Dave.

Quote:

---

I am quite sure there is a market for a credit card-sized RPN calculator.

---

RPN would not be the main feature, the fact it's a credit card sized *scientific* calculator would be the novel thing. I doubt too many people would get too excited about a credit card RPN 4-Banger. And it's open source and reconfigurable too.

Dave.

I don't want to spoil all the fun you have, but considering I can get a credit card sized calc off ebay for $1, I would not pay $60 - rather $10 for an RPN version.

Secondly, a true credit card calc would have to stay alive in a wallet in my back pocket. Can that even be done?

Anyway, cheers to this great idea!

Quote:

---

I don't want to spoil all the fun you have, but considering I can get a credit card sized calc off ebay for $1, I would not pay $60 - rather $10 for an RPN version.

---

Every other credit card calc on the market is a 4-Banger.

This has nothing to do with it being RPN, it's the fact that it's a full *scientific* calc, and it'll probably play chess too :->

If there is a scientific credit card calc on the market then let let me know and I'll stop all this foolishness!

Quote:

---

Secondly, a true credit card calc would have to stay alive in a wallet in my back pocket. Can that even be done?

---

No idea, that needs to be tested.

Gotta think outside the square too, credit card calcs don't necessarily have to go in your wallet...

Dave.

Quote:

---

Every other credit card calc on the market is a 4-Banger.

---

And earlier:

Quote:

---

albeit the worlds first(?) scientific one

---

While it is true that there are no scientific credit card sized calculators on the market, it isn't true that there haven't been any. The Casio fx-98 for example -- a photograph was posted in the recent form factor thread.

It will be the first RPN capable credit card sized calculator and likely the first in this form factor to play chess and the first solar powered chess computer.

- Pauli

Quote:

---

the fact it's a credit card sized *scientific* calculator would be the novel thing

---

Quote:

---

*rolling eyes*

I guess that's what I get when I show this on a HP forum!

---

Quote:

---

I thought the fx-98 was that already.

---

Close, but no cigar. It is 90mm x 59mm x 6mm

And of course, discontinued maybe 20 years ago? Fairly rare even on eBay.

Dave.

Hello!

Quote:

---

The Casio fx-98 for example...

---

... or the Soviet Elorg 38 (stat/math with two shift keys). Unfortunately, those were of very poor build quality. Mine has a leaking LCD, very unresponsive keys and intermittent battery contacts.

Regarding the original idea: Yes and no... Yes, because a small RPN programmable would be appealing, no, because credit card size is too small, a membrane keyboard is a no-no-item for me (learnt to hate it with the Sinclair ZX-81) and most importantly: If it dosen't glow in the dark, I don't want it :-)

Greetings, Max

Quote:

---

Regarding the original idea: Yes and no... Yes, because a small RPN programmable would be appealing, no, because credit card size is too small, a membrane keyboard is a no-no-item for me (learnt to hate it with the Sinclair ZX-81) and most importantly: If it dosen't glow in the dark, I don't want it :-)

---

I'll ship a free head torch with every unit!

Dave.

Hello!

Quote:

---

I'll ship a free head torch with every unit!

---

:-)

I'll get one then... but only if the head torch has a red led in it!

Greeting, Max

You can convert the torch to red in several ways. A piece of red plastic works well but better is finding two pairs of red/green 3D glasses and taking one lens from each.

- Pauli

Attractive design for a first draft.

Proposal: replace 10^x with y^x.

Remarks:

• Don't understand yet how you differentiate between STO and RCL. Same for E and PI. Some prefix keys may be inevitable.
  
• Please use math symbols wherever possible, e.g. for SQRT.
  
• Credit card scientific is a nice idea. With its RPN option it's even nicer. A nice toy. Maybe a bit too small to be really useful.
  
• IMHO tactile feedback is a must.
  
• I'll definitively not play chess with this.
  

HTH

Walter

Prefer this option as this allows the X and Y reg to be displayed at the same time.

Any idea of the key layout - a credit card is a bit small for a voyager look alike!

Mike T.

The voyager layout couldn't have been all that bad - after all the HP12C is still going strong!


Obviously an exact copy of a voyager keyboard isn't possible (or desirable) - but the key layout needs to work and be 'logical' with similar functions grouped together vertically or horizontally.


For example -

sin,cos,tan / sin-1,cos-1,tan-1

deg,rad,grd

fix,sci,eng

ln,log,yX / eX,10X,1/x

int,frac,abs

enter,chs,eex,clX

+,-,/,* (obviously!)

gto,gsb,rtn

sto,rcl (defiantly unshifted!)

sst,bst


Fitting that in, and more importantly deciding what to leave out, is probably going to be the hardest part of this project...


Just my 2c worth.


Mike T.

HP 15C style as described above but with a clock (dynamic functions similar to the HP 41C) and alarm. At least 32kb of memory, with the standard RPN like keystroke programming.

Sort of like a supercharged HP-15C (HP41C cross HP 42S hybrid) in a 15C package for the shirt pocket, not my back pocket wallet. 8-)

UWatch is working perfectly!

Cheers, Geoff

here is my take on this idea,

firstly, although cc ucalc would be cool, it certainly wouldn't be anything new or indeed have much going for it against historical offerings.

having something as small as a credit card is, i think, not totally necessary. for example, something the size of a voyager is small enough already. In the past i have owned two calculators the size of credit cards. one was a casio (4 banger) and i can't even find a picture of it on the internet. it was literally the dimensions of a real cc, about 1mm thick. i put it in my wallet with my actual cards. after a while it snapped.

the other one was a very beautiful all metal design by sharp. about 2mm thick. i can't find any reference to it on the internet either. it was solar and very, very elegant. i used to carry it in my back pocket and eventually it took on the curvature of my bum - but it still worked perfectly. to this day, i do not know what happened to it.
i would like to advance the proposition that what we want here is something not already done; a calculator the size of a voyager (ie pocket sized) with a powerful programming language. a scientific is not enough. we have that already.

as Geoff says, a supercharged 15c!

Quote:

---

While it is true that there are no scientific credit card sized calculators on the market, it isn't true that there haven't been any. The Casio fx-98 for example ...

---

The Casio fx-98 is from 1985. The Casio fx-48 is from 1978, and is even smaller than the fx-98, but has no solar cell. The Radio Shack EC-4009 is an enhanced fx-98.

Both my 31-year old fx-48 and 24-year old EC-4009 still function perfectly, and show no LCD deterioration.

As far as having a micro-SD capability, how would that be possible (especially write operations) in a calculator that is solar-cell-powered only?

To me the Voyager is NOT pocket size, never has been, never will be. Yet many seem to see it as the "ideal" pocket size, I'm not sure why...

The Casio FX-98 is more what I think a true pocket calc should be. The only one that comes close to this these days is that cheap no-name asian one discussed some time back.

The credit card size fixation is only because, well, it's something to shoot for. I could go smaller or I could go bigger. Same for the thickness. To me the project is just an exercise in clever product design which is what I enjoy doing.

IMO a voyager size calc HAS been done before, and you can still buy them, but a credit card size scientific programmable calc hasn't, so I think the CC is actually the more novel idea. Not as practical maybe, depending upon your viewpoint, but it's the more novel.

I don't anticipate anyone actually putting it in their wallet and bending the thing, obviously it won't survive as the LCD glass will likely just crack.

So what's the point?, I dunno, it's just cool. I like someone's idea of hanging it around your neck as nerd bling!

The problem is, if you ask a hundred different people you'll get a hundred different answers about what they want :->

Then of course, if you say do a Voyager size calc then there is not as much point making it so thin, so you make it thicker and start adding features, and then you decide you might as well have batteries and a nice alloy case, and then people will want proper tactile keys again, and... etc...

Dave.

Edited: 15 Nov 2009, 7:42 p.m.

Quote:

---

As far as having a micro-SD capability, how would that be possible (especially write operations) in a calculator that is solar-cell-powered only?

---

You are likely right, I'll only have a few mA available. Maybe enough for a very slow read cycle, but probably not enough for writing. I've haven't looked into low power SD card operation though.

Same with the USB interface which has to run at 8MHz primary and faster internally. Probably not possible with just the one small solar cell.

Dave.

Quote:

---

Same with the USB interface which has to run at 8MHz primary and faster internally. Probably not possible with just the one small solar cell.

---

USB supplies copious amounts of power, so there shouldn't be a problem.

A non-writable micro SD card isn't a lot of use but still allows importing things. Could the supercap be used to allow slow writes?

- Pauli

Quote:

---

Heathen! Just wait for the revolution ... you'll be lined up against the wall ...

---

I prefer to start my own revolutions, it's much more fun being a heathen!

Dave.

If it is truly credit card size, then you can package together one of those hard plastic case/covers that have been used to protect credit cards. I remember seeing some of these plastic cases a number of years ago in Europe.

--Sancerre

Quote:

---

To me the Voyager is NOT pocket size, never has been, never will be. Yet many seem to see it as the "ideal" pocket size, I'm not sure why...

---

Dave, if it fits in my shirt pocket without extending a few inches above the pocket, it's pocket size. The Voyager's are pocket size. The 35s, 33s, 17bii+, all those are not pocket size.

12c going in my pocket.

12c already in my pocket.

I'm intrigued by what you are doing, and I commend you for it, but the thought of a calculator the size of a credit card with 8 buttons going across it, I don't know, these old fingers probably can't do that. The few credit card sized calcs I have seen and used I eventually threw away because (a) the buttons were too close to each other for these old fingers, and (b) the LCD display was generally so tiny that I had trouble reading it. They were just impractical, from a usability perspective. The Voyager buttons are easy to press and the display is, to me, just right. And the 12c, while a financial calculator, is RPN keystroke programming at it's simplest and is the finest made today.

But I'll follow your project because I am intrigued and you know what you're doing!

Don

Quote:

---

Dave, if it fits in my shirt pocket without extending a few inches above the pocket, it's pocket size. The Voyager's are pocket size. The 35s, 33s, 17bii+, all those are not pocket size.

---

The actual fact it can fit in someones pocket is, to me, moot.

"Pocket size" to me isn't just about fitting in some shirt pocket, it's about being generally as small as can be so it doesn't take up as much room wherever you put it. In a pocket, on the desk, sitting on a catalog or datasheet etc

The voyager just isn't small enough IME. The Casio FX-260 solar is smaller than a voyager for example, and that ain't the only one on the market.

Quote:

---

I'm intrigued by what you are doing, and I commend you for it, but the thought of a calculator the size of a credit card with 8 buttons going across it, I don't know, these old fingers probably can't do that.

---

The current design is 10mm key spacing horizontal, and 8mm spacing vertical.

Dave.

Quote:

---

The current design is 10mm key spacing horizontal, and 8mm spacing vertical.

---

Which is about 2mm less than my poking finger in both directions :-(

- Pauli

Dave;
I've got a neck ready to hang it from all ready. I only want to re-assign three keys and that'll be a good first thing to learn on it.
A clock function would be nice but i guess it would only be practical at the poles near summer solstice.

Quote:

---

Gotta think outside the square too, credit card calcs don't necessarily have to go in your wallet...

---

For me, a credit card sized calculator definitely would have to fit in a wallet. Otherwise it would have no appeal to me whatsoever. I would grab a 15C if I only needed a rather small one - or use my phone that I already carry around. So, not-for-wallet-use would be an absolute show stopper.

BTW, the Kadio KD-1005 credit card sized calc was a door prize at this year's conference. Maybe Gene Wright knows where to buy them...

Edited: 16 Nov 2009, 5:19 a.m. after one or more responses were posted

Yes, that Kadio costs $0.50ea in 5K volume, I got a quote a year or two back. Almost certainly the smallest scientific calc on the market today.

Dave.

Interestingly, the same width and height as the long gone Casio fx-98. 4mm thicker though.

I've thought about trying to get half a dozen of these on a couple of occasions.

- Pauli

Edited: 16 Nov 2009, 5:29 a.m.

Dave might be able to answer this (at least in time anyway).

How much headroom is there in the power supplied by the solar cell? I.e. will this be usable indoors? I've found a 4mm thick one but there are complaints about the solar cell not powering it unless there is lots of light. Interestingly, the 7mm thick one doesn't have these complaints.

- Pauli

The one I'm looking at is rated at 12mA @ 1.5V

22mm x 7mm x 1.6mm

The price of the solar cell alone is twice the price of those entire calcs!

Claims to work indoors, but I'll have to get samples to actually test it.

I'd be surprised if I don't have enough juice to run any size processor at 32KHz/250KHz, plus the LCD under any light. If it doesn't work indoors in poor light then the project is probably the tube. I've gone off batteries now!

An RTC might be possible with a supercap just running a seperate RTC chip.

Dave.

Edited: 16 Nov 2009, 6:08 a.m.

Quote:

---

An RTC might be possible with a supercap just running a seperate RTC chip.

---

Is it going to last a week or three without light? If not, I don't see the point...
Even if it does I still don't see the point :-)

- Pauli

Quote:

---

Is it going to last a week or three without light? If not, I don't see the point...
Even if it does I still don't see the point :-)

---

Dunno, have to do some calcs and maybe some measurements.

Might be handy for those that leave it on their desk all day, or stick it on their fridge, or whatever...

But I won't lose any sleep over not having an RTC.

Dave.

Crotch moistening stuff for the fanboys: :->

Well, what do you know...

Change the horizontal key spacing to 8.5mm and the dimensions look perfect for a Voyager style key layout, with extras. Almost as if it was destined to be in a credit card size (this is a true credit card size, not the bigger FX-98/Kadio size)

Yes, complain all you like about the key assignments, it's an example, albeit one I don't mind...

Dave.

Edited: 16 Nov 2009, 7:30 a.m.

You forgot the stylus holder, which you will need with keys that small.

: )

Wow! Thanks.

It has probably been brought up before, but, why the alpha assignment starting at the bottom with A and working upwards.

Not refering to HP (although they all follow the same standard), but my Aircraft FMS and the ACARS keypad are:

A   B   C   D   E  

F   G   H   I   J

K   L   M...

This would be the first keypad I have seen with the alphabet starting with Z (zee or zed) first and working towards A.

Cheers, Geoff

Quote:

---

You forgot the stylus holder, which you will need with keys that small.

---

It's bigger than the uWatch key spacing which had 8mm x 5mm, and I find that perfectly usable, considering the size of course.

I can go back to a bigger layout, but then bye-bye voyager compatability. A more standard 11-12mm layout would give 21 keys in the bank. That's 4-banger territory. Functions can be in menus of course, just like the uWatch, but that kinda sucks.

It's the size of a credit card remember, there are trade-offs...

Dave.

Quote:

---

It has probably been brought up before, but, why the alpha assignment starting at the bottom with A and working upwards.

---

Because I'm a PCB designer, and hence naturally think of bottom left as the origin of everything :->

Dave.

You are a rare breed!

Any chance of CORRECTING it!

8-0   8-)   ;-)

Edited: 16 Nov 2009, 3:46 p.m.

half joking observation, for amusement.

Ok Dave, the shocking truth is that you are turning into a calculator manufacturer!

Indeed! But not mass market like HP, TI, Casio, Sharp etc, what you want to address is the exclusive market, the executive market, the celebrity market and the specialist market; the kind of market segment also occupied by designer labels in the fashion industry.

Someone noticed that the head of RBS UK uses a 12C (from photo). But hey, that’s not going to impress nowadays. He needs an upgrade. What about city finance types. What do they use when not at their PCs? Their iphones maybe? Surely they’d prefer a more executive device, with buttons on it.

Suppose im an architect, out in the field talking to my clients about a multi billion development. do I pull out a TI or one of the new, low end, HPs when they ask about cost alternatives. No! Either I have to juggle a clumsy laptop or maybe, just maybe, use an old style HP. Those days are numbered. this guy is your customer!

What im talking about is a definite but small market segment of high quality and expensive, executive calculators. Think Hi-Fi, where you get all these little companies, of just a few people, but they’re making a business in the expensive but exclusive high end.

Forget low end. You’ve no chance. You’re only route is expensive high end, but superb quality hand held calculators. These must excel in screen, keyboard and build materials. We’re talking stainless steel or titanium case construction. Proper metal domed keys and hi-res greyscale screen, that’s also good in sunlight and retailing around $500. Really that’s still cheap in comparison to smart phone prices, which people seem happy to spend.

Synopsys: Blinged up, supercharged 15c+12c+16c with bigger screen, alpha, usb interface and two programming languages; voyager classic and modern procedural.

… the hard part is dreaming up the model numbers :-)

Would anyone buy one?

I would given a clock, alarm, no graphing and oodles of program in simple RPN keycode format.

Cheers. Geoff

Hugh, I might make it to London without the airplane. Wife wants to install hardwood floors and wants me to get lost. I will let you know!

Careful Hugh, you are starting to sound like another Hugh I know! :->

To answer your question first, who'd buy one? Well, not me, nor anyone else on this forum I'm fairly sure. This has actually been discussed a bit not too long ago.

What does that mean? Well, several things are guaranteed with such an approach:

1) Lots of NRE cost

2) No short or mid term return on any investment

3) High risk

4) A very unhappy wife!

Something like what you propose is getting into the steampunk/designer/art category, and really that's something I am not ashamed to say I suck at.

I do really like that sort of stuff, and I'd love to design such a "designer" calculator, but believe I really lack to skills to do so even if I wanted to. I could probably learn, but those kinds of designs take lots of time and NRE.

Don't get me started on high end Hi-Fi stuff, please!

I can't see my calculator designs ever being "commodity" low end designs sold in stores, they will always be niche market higher priced calcs. And the key to getting a niche market is to make something novel.

The reality is that the risk/reward for the high priced high end market is astronomical compared to my current "good enough" calculators for a (much) bigger niche market (e.g. geek toys, uWatch, uCalc) where I am practically guaranteed to get my money back and then some.

Dave.

Edited: 16 Nov 2009, 6:57 p.m.

Can't we have go faster iridium strips and oxygen free copper directional battery contacts? :)

- Pauli

Quote:

---

Can't we have go faster iridium strips and oxygen free copper directional battery contacts? :)

---

Sure, and they can be manufactured by nude virgins in utopialand!

Cryogenic freezing is optional.

Dave.

Quote:

---

12c already in my pocket

---

Quote:

---

You are a rare breed!
Any chance of CORRECTING it!

---

If I must!

Hey, I just realised that with 10 keys wide it could be in QWERTY format!

Dave.

I think Walter has done a Voyager layout with a QWERTY alpha mode.

- Pauli

Geoff, I can understand why you want RTC functions, given your flight calculations. But how many others really need it in a credit card calulator? I agree with the keystroke RPN programming without graphics capability.

Then again $500 is a bit much for me.

what. you get to party whilst the wife does the DIY. excellent!

That goes back to 2005. I found the links in the archives being broken, however, so I dug through my old files and excavated this from the summer of 2006. FWIW it shows a way to do it.

FWIW is right. Ten columns of keys is too many on a credit card ;-)

- Pauli

Quote:

---

FWIW is right. Ten columns of keys is too many on a credit card ;-)

---

The membrane makers agree. They couldn't give me a quote, said the 8.5mm spacing was too close.

So it's bigger spacing and/or back to cap touch sense.

I think reality should probably kick in here. Such a spacing is fine on a calc watch, but with the relative luxury of credit card size, a bigger spacing should be aimed for. After all, 25 keys works on the uWatch with all it's powerful features.

My cap touch sense chip supports 24 keys...

Dave.

Quote:

---

Sure, and they can be manufactured by nude virgins in utopialand!
Cryogenic freezing is optional.

---

Quote:

---

I think reality should probably kick in here. Such a spacing is fine on a calc watch, but with the relative luxury of credit card size, a bigger spacing should be aimed for. After all, 25 keys works on the uWatch with all it's powerful features.

---

I believe it is possible to design a usable layout for a
non-programmable, RPN scientific calculator with as few as
20 keys. I uploaded an "HP4S" design to this forum a while
ago, but I cannot find it at the moment. I think I still have
the picture at home, and will upload it again tonight.

Dave,

Your original layout had 4 rows x 8 columns. If you drop the 'F' keys above the display (a silly place for keys, IMO) you'll have roughly a 10mm x 10mm space for each key. That's approximately the same spacing that HP uses on the top rows of the 20b -- which is quite usable aside form the lack of key clicks.

Assuming a double height ENTER, that leaves 31 keys, more than enough for a programmable scientific calculator especially if you use 2 shift keys.

-Katie

Quote:

---

I uploaded an "HP4S" design to this forum a while ago

---

Here is the thread

Massimo

Here is another go, this time with 24 keys which fits my cheap and low power touch sensor chip.

10mm key spacing.

3 more keys could be added if the membrane idea is possible again.

I rather like this one.

Two shift functions (press once or twice), with the 1st shift your most common functions, and the 2nd shift mostly base conversion stuff.

6 menu keys like the uWatch, but not directly under.

Dave.

Why isn't F1=1, F2=2, ... ?

Quote:

---

Why isn't F1=1, F2=2, ... ?

---

No other reason than the match the uWatch.

Doesn't quite look right though does it...

Dave.

This looks awesome, and I would definitely buy one, but why no built-in stats? :(

The menu button caters for all requirements :-)

Pauli

Quote:

---

The menu button caters for all requirements :-)

Pauli

---

Yeah, unfortunately you can't have everything on the dedicated keys. So I was selfish and chose what is most useful to me :->

All the other stuff gets booted to the menu system, which actually worked quite well on the uWatch.

Of course, depending upon what key topology I eventually use, if you want to change the overlay you might be able to. There could ultimately be multiple versions on offer.

The solar cell is on it's way, so I can see what's possible...

Dave.

Edited: 17 Nov 2009, 8:32 p.m.

Quote:

---

Of course, depending upon what key topology I eventually use, if you want to change the overlay you might be able to. There could ultimately be multiple versions on offer.

---

The two line display lends itself to Free42, I'd be interested in playing with a port if the key configuration is compatible, or can be made to be compatible with a different overlay.

I can understand the limitations of such a small piece of hardware. Still it is always nice to have a "E+" (pretend the E is a sigma) key, and dedicated stats registers. I suppose I could be asking too much, and maybe I am spoiled, but all my RPN calcs have had that :)

Anyway, very cool project, and I'm sure it will be a fantastic calculator one way or another.

Quote:

---

all my RPN calcs have had that

---

I wish that were the case for all the RPN calculators that I have, I'm referring to the 17Bii, 20b in particular. Unfortunately, the ones with list-based stats don't have Sigma+ and dedicated stats registers and are harder to use for simple statistics. List-base stats are really only useful on larger data sets and I doubt that anyone would work with those on a calculator.

-Katie

Quote:

---

all my RPN calcs have had that

---

Absolutely. Major design goof, IMHO.

Hi, Dave. Sometime ago I reached at your incredible watch! It was a great surprise to me see that someone could have done such work!
After the surprise, I think about your project and could only complain about it hasn't programm capabilities and, of course, the R/S key.
As you are a geneous in this area, I believe, in my opnion, that two models: one with chess and other games and another programmable, with other great functions, like timestop, watch and calendar, as in your watch. A usb connection is great, as you say, in the case of firmware upgrades and to receive programs (somthing like the 41C modules, but only the files being transfered to calc). I would just try do not crow the keyboard and use some function keys and a soft menu associated to them... of course, in programs I could use such capability too (like 48 series).
Any way, even it was done of wood, I would by one, as it is a piece of human inteligence, fitting or not into my wallet (in my college time, I was very proud of carrying my 15C in a special wallet).
Put me in you your list!
Artur

+1 for simple keystroke programming (e.g. HP-25'ish). That'd make it about perfect for 90% of my requirements.

Thanks for posting your ideas - this is just fun to think about!

Cheers,
Bob

Quote:

---

+1 for simple keystroke programming (e.g. HP-25'ish). That'd make it about perfect for 90% of my requirements.

Thanks for posting your ideas - this is just fun to think about!

Cheers,
Bob

---

Everyone is going to have quite different requirements, that is why it's almost certainly not possible to please a majority with the layout and functionality.

The good thing is that it is open source, so if you don't like the way it works then you can change it to suit your needs.

And hopefully you'll just be able to stick on an overlay to get any look or key layout you like.

This should be interesting, I'm looking forward to getting the solar cells in the next day or so and playing around. Then hopefully some prototypes will emerge that should be pretty close to the final product.

Dave.

I don't quite get this. It's just as easy for me to press INPUT after each data point as it is to press Sigma+.

I've now found a suitable 132x32 full graphic display, with a large 51mm x 15mm display window. This will allow all sorts of display options, like 2x16 (8x16 font), or even 4x22.

Dave.

What other kind is there?

:D Hmmh, you're right. Those other folks don't need transcendental functions at all, do they? So they shall be fed with 4-bangers d;)

Here we go! All the fun starts with a proper display. If you need some small fonts (6 or 7 pixels high) there are proposals also beyond Luiz' work.

Dave,

Do you have a manufacturer & part number or link to a data sheet for the enclosure? I'm curious to see what it looks like or what you have in mind.

Thanks, mate.

Quote:

---

Do you have a manufacturer & part number or link to a data sheet for the enclosure? I'm curious to see what it looks like or what you have in mind.

---

There effectively is no enclosure, the board itself becomes the case. It should actually look like a credit card, this isn't just what the font panel will look like, it what the entire calculator will look lke:

3mm thick if my plan works.

Dave.

Edited: 19 Nov 2009, 2:27 p.m.

exchange:

F1 4 to F 4

F2 5 to F 5

F3 6 to F 6

F4 1 to F 1

F5 2 to F 2

F6 3 to F 3

:-)

I just tried my solar cells, and well, it was pretty disappointing. These are supposed to be primo parts, with the cost to boot. But all I could manage, even with 5 of them in parallel was 170uA short circuit current at my work desk (which is surrounded by big windows).

My 132x32 graphic display alone needs 140uA @ 3V.

In full sun and outside in the shade or near a window they are fantastic, I could run a LED torch direct, but that doesn't help much.

Could possibly work with some form of storage like lithium ion, but if it's flat you have to wait for it to charge up first. Not exactly a good practical solution though.

So it's looking like solar is only fully practical with maybe the 14 segment display and a flea power processor. And then you'd have to scrap the touch chip anyway.

*sigh*

Dave.

Edited: 19 Nov 2009, 8:42 p.m. after one or more responses were posted

:-(

Are two 14 segment displays and a tiny processor possible?

8 characters are really marginal.

I guess this also writes off the micro SD card.

- Pauli

Quote:

---

Are two 14 segment displays and a tiny processor possible?

8 characters are really marginal.

I guess this also writes off the micro SD card.

---

Not possible in a credit card size.

Looks like battery power is the only viable option.

Dave.

Since you need to use a battery, how about an EL back light on whatever display you end up using? Their must be a cheap, tiny 3V to 90V inverter for all those watches that that have back lights.

-Katie

No room, sorry.

Dave.

dave;
those solar cells are getting better all the time. i hope you build us a new toy now. in a year or two you will have the power you need, or more miserly processors and can make make your dream - a.k.a. our next-next toy. - db

Quote:

---

in a year or two you will have the power you need, or more miserly processors and can make make your dream - a.k.a. our next-next toy.

---

Dave, is ePaper (electronic ink) available in CC size? The whole thing could just consist of of a touch sensitive display and a solar cell. epaper only consumes power when updated not for the display itself.

Quote:

---

Dave, is ePaper (electronic ink) available in CC size? The whole thing could just consist of of a touch sensitive display and a solar cell. epaper only consumes power when updated not for the display itself.

---

Yes, they are available in small sizes, but are all custom by the looks of it. The dev kit alone is $1500 8-(

Dave.

How about a supercapacitor that charges all the time from the solar sells. These guys seem to make some pretty low profile ones:
http://www.tecategroup.com/ultracapacitors/cap-xx.php

Not sure if you can get enough storage to power the screen but might be worth looking at.

Can I ask how big your solar cells are? It doesn't sound right. If you only need 140 micro-Amps, then there are cells that should be able to deliver that that are only 1mm on a side. You'd then have to hook up about 4 (probably 5 to be on the safe side) in series to get over 3 volts.

In full sunlight with 16% efficiency monocrystalline solar cells, the theoretical output should be around 160uW/mm^2 ... but under typical domestic indoor lighting, a quick guesstimate (based on photographic exposure values) tells me that you might get 160nW/mm^2 (in photo parlance, 10EV difference or about 1/2^10). This ignores the cell's spectral response and possible non-linear output vs. illumination level.

From this I'd expect a 5 X 20mm panel to put out c. 16uW or less in your living room and up to 16mW at noon in your front yard.

This all reminds me of when I used to wait tables in a coffee shop (late shift). We had a lot of college students who came in for late night cramming sessions, and one night one of them kept lighting his butane lighter and holding it over his work. Finally, I came over to see what he was doing. He said he couldn't get a square root on his solar powered calculator unless he flicked his Bic. Good thing he didn't try any big factorials--he would have had to burn the place down...

DATASHEET

These were the best ones I could find on the market.

I need say 200uA @ 3V (600uW) to run the LCD and processor.
At least double and maybe more for the touch chip.

Like I've said, it may be possible with the 8 character 14 segment display, a flea power micro, and membrane keypad that takes no power. But the usefulness is limited, and the membrane keypad requires $400+ NRE.

Dave.

Edited: 20 Nov 2009, 3:52 p.m.

Quote:

---

How about a supercapacitor that charges all the time from the solar sells. These guys seem to make some pretty low profile ones:
http://www.tecategroup.com/ultracapacitors/cap-xx.php

Not sure if you can get enough storage to power the screen but might be worth looking at.

---

I already have some, but it would be pretty silly to take your calc out of a dark place (shirt, draw, pocket, wallet etc) and have to wait for it to charge up before you could use it.

Dave.

Yeah, the incredible dynamic range of your eyes can be misleading when trying to estimate where/when PV cells will work.

Lithium primary cells store a lot of power, but you'd have to make arrangements for removal/replacement and that might add bulk.

Maybe a Li-poly, or Li-Ion coin cell, with USB charging? They'll hold a charge for quite a while and there's plenty of single chip battery management solutions.

Cheers,
Bob

Edited: 20 Nov 2009, 4:45 p.m.

Alright I'm new here but I was searching for different small power sources and came across this article from Slate and got a pretty good chuckle:
http://www.slate.com/id/2193827/

If I'm out of line here, please let me know.

Another thought, the 14 segment display and a second smaller 7 segment display in the two and a half digits to four digits range. This would solve the lack of digits nicely.

- Pauli

Quote:

---

Another thought, the 14 segment display and a second smaller 7 segment display in the two and a half digits to four digits range. This would solve the lack of digits nicely.

---

Not a bad idea at all.

I like separate exponent displays.

I took a quick shot of some segments I was able to light up with static charge on the 14segment display to show the contrast:

It's darker than the image shows, very nice contrast.

Disadvantages of a 14 segment display version, apart from only 8 digits + exponent, are increased thickness (4mm + membrane/domes), lower power processor (say MSP430 or PIC nanowatt), plus significant NRE cost for the membrane metal dome keypad. But complete solar power would be possible I think.

Dave.

Quote:

---

I like separate exponent displays.

---

Me too, ever since I first got my now long dead Casio FX-602P.
Are 2.5 - 4 digit LCD displays available in a size that will fit?

Quote:

---

Disadvantages of a 14 segment display version ...

---

These aren't really disadvantages if the alternative is something that cannot work :-)

If the keypad NRE is going to be too bad, I'm sure some donations would be possible. I certainly would be willing too.

- Pauli

I'll opt for the battery (or even dual) powered version, especially if programming or list based operations are involved. A low profile Li cell with a slot-in mechanism would be fine for me.

I have a watch that uses a coin lithium solar rechargeable cell. it shuts off in the dark, keeps time and resets from WWWB time signals.
I see coin rechargeables seem available, even to the CR2032 size used by HP calculators. Even a small rechargeable might suffice. sam