Author Topic: EEVblog #1078 - World's Thinnest Calculator Teardown  (Read 4031 times)

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Offline EEVblog

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EEVblog #1078 - World's Thinnest Calculator Teardown
« on: April 25, 2018, 09:32:06 am »
A look at the amazing construction techniques used in the world's thinnest calculator by Casio
Destructive teardown on the Casio SL800 credit card calculator from 1983.
It's more interesting than expected!


 
The following users thanked this post: SeanB, ez24

Offline DeanCording

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #1 on: April 25, 2018, 10:13:58 am »
Those caps would probably be for power storage for the solar cell.
 

Online Bud

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #2 on: April 25, 2018, 11:13:20 am »
I've seen iso 7816 cards that make sound, cards with Red 7-segment LED looking display, and cards with a fingerprint sensor  :-+
 

Online Mr. Scram

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #3 on: April 25, 2018, 11:54:12 am »
It pains me to see it destroyed, but it was for the benefit of us all.
 

Offline Rerouter

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #4 on: April 25, 2018, 12:28:48 pm »
So now the question falls to you dave, can you find glassless LCD's and build using reccessed capacitors to make a V2 of your prototype with a much tighter PCB sandwitch

On the topic of very thin boards, How would you describe to a PCB house to have a routed out area that does not cut through the entire board cross section, a dip or a void with the opposite surface left intact?
 

Offline Tek_TDS220

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #5 on: April 25, 2018, 01:18:42 pm »
Looks like a layer or two of prepreg to me, not flat-flex.  You can tell by cutting through the board.  You'll see fibers if it is prepreg.  A variety of prepregs are commonly available down to 60 um (with 106 glass).
 

Offline EEVblog

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #6 on: April 25, 2018, 02:47:29 pm »
So now the question falls to you dave, can you find glassless LCD's and build using reccessed capacitors to make a V2 of your prototype with a much tighter PCB sandwitch

Oh boy, don't me started...

Quote
On the topic of very thin boards, How would you describe to a PCB house to have a routed out area that does not cut through the entire board cross section, a dip or a void with the opposite surface left intact?

Two ways:
1) Controlled depth route. Not very effective/useless on thin boards. But cheap'n'cheerful.
2) Tell them to route the pre-preg layers first before they glue them. This will incur extra cost, but it will give you a perfect recess. Easy if you are already doing a multi-board, especially with bling /burried vias. On a standard double sided board they'll have the make up the board thickness with multiple pre-pregs. Something easy would be say 0.8mm + 0.8mm with 0.8mm depth route.
 

Offline Fungus

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #7 on: April 25, 2018, 02:59:54 pm »
Regarding the buttons:

Wouldn't the resistance change with pressure even if the carbon pads were always touching? Maybe they work by looking for changes in resistance.


Edit: Now watch the prices of these skyrocket on eBay.
« Last Edit: April 25, 2018, 03:19:00 pm by Fungus »
 

Offline gamalot

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #8 on: April 25, 2018, 03:21:24 pm »
I once had one Casio look like this when I was in high school in the late 80s.
 

Offline EEVblog

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #9 on: April 25, 2018, 03:22:19 pm »
Regarding the buttons:
Wouldn't the resistance change with pressure even if the carbon pads were always touching? Maybe they work by looking for changes in resistance.

I wouldn't want to engineer it like that. The spacing seems quite deliberate.
 

Offline Fungus

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #10 on: April 25, 2018, 03:48:41 pm »
Regarding the buttons:
Wouldn't the resistance change with pressure even if the carbon pads were always touching? Maybe they work by looking for changes in resistance.
I wouldn't want to engineer it like that.

You might not have a choice if the requirement is "0.8mm".

I don't see why it would be more difficult than the capacitive sensors on your watch.
 

Offline VEGETA

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #11 on: April 25, 2018, 03:55:57 pm »
Isn't it the time for engineering calculator shootout? I used to own a Casio (a silver one) which costs around 25$. I wonder what is the best these days for someone to buy, this could be a nice topic for a new video.

I think credit-card sized calculators are nice, but are they practical? I mean, do people really use them instead of real calcs?
 

Offline Fungus

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #12 on: April 25, 2018, 04:06:23 pm »
Isn't it the time for engineering calculator shootout? I used to own a Casio (a silver one) which costs around 25$. I wonder what is the best these days for someone to buy, this could be a nice topic for a new video.

a) What do you define as "engineering"?
b) Isn't there an app for that?
c) It wouldn't be impartial, Dave is very brand-biased.  :popcorn:

GOTO 27m40s


I think credit-card sized calculators are nice, but are they practical? I mean, do people really use them instead of real calcs?

I remember people using them back in the day. Mostly they were freebie/promo giveaways like the on in this video.

These days people use their smartphones.
« Last Edit: April 25, 2018, 04:09:14 pm by Fungus »
 

Offline EEVblog

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #13 on: April 25, 2018, 05:53:00 pm »
You might not have a choice if the requirement is "0.8mm".
I don't see why it would be more difficult than the capacitive sensors on your watch.

Totally doable with separated distance in 0.8mm IMO.
Also, if all the keys touched all the time, that's a lot of extra current draw in idle, plus the requirement to measure it in a meaningful amount of time if it's high resistance.
 

Online TheSteve

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #14 on: April 25, 2018, 06:29:26 pm »
Not in the same ballpark thickness wise but probably inspired by the calculator.

The Motorola "Confidant" numeric credit card pager.
VE7FM
 

Offline Rerouter

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #15 on: April 25, 2018, 09:14:45 pm »
Well to get you started, it appears there are single color, flexible reflective lcd's on alibaba that resemble the one shown in the video.
Find one in the right form factor, and you may be set for a very thin screen.
https://www.alibaba.com/product-detail/flexible-transparent-display-flexible-transparent-lcd_60667954126.html?spm=a2700.7724857.main07.141.26471f05NcMM24

Combine it with the printable solar panel flims like mikeselectricstuff reveiwed and you could just pull of a modern version.

Then using something like this for power (not insane power density, but for an LCD calculator, it should be low)
https://www.digikey.com/products/en/capacitors/electric-double-layer-capacitors-edlc-supercapacitors/61?k=&pkeyword=&pv1500=1231&FV=ffe0003d&quantity=0&ColumnSort=0&page=1&pageSize=25

 

Offline Skashkash

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #16 on: April 25, 2018, 11:43:42 pm »
 Air pressure helps to provide a "spring" effect to keep the conductive carbon away from the pcb contacts.
 
  It's why you have that inner spacer layer with channels between buttons to equalize the pressure between the switch "cells" when you press a button. 

Had similar (but much larger) keyboards on some equipment back in the 80's. If the plastic got punctured over one of the buttons, the top layer would actually deflate and we'd have to toss whole keyboard.
 

Offline blackjetrock

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #17 on: April 26, 2018, 01:15:07 am »
You can get at the die with a torch, no acid required:



Also, I have an Olympus like yours (I got it after I saw yours...) and I have a nice XY slide holder so you can move stuff around. Did yours not come with one? They are available on ebay quite cheaply.
 

Offline Fungus

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #18 on: April 26, 2018, 02:01:24 am »
Totally doable with separated distance in 0.8mm IMO.

Ok, I can't claim to be an expert there.

Also, if all the keys touched all the time, that's a lot of extra current draw in idle

Not necessarily true if it's doing a matrix scan - not all the keys will be powered up all the time.

Plus: Does it matter in a solar powered device? So long as it works under normal conditions (single keypresses) then it's fine.

But, whatever. If you don't see any problems with tolerances for the keypads then we'll do it that way.
 

Online rsjsouza

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #19 on: April 26, 2018, 04:08:09 am »
Also, if all the keys touched all the time, that's a lot of extra current draw in idle
You gave me something to think about. I recall that if you pressed several keys on some old calculators the LCD would dim considerably - I never thought that power consumption could be a possible cause.

Dave, you rave about Casios and I grew up loving them as well, but in terms of durability they leave a lot to be desired. They seem to have embraced more than anyone the zeitgeist of disposable electronics of the 80's: I have several 1980 and 1990's calculators/scedulers/gizmos from them (including a "film card" SL760, several fx-39, among others) that have their crappy membrane keyboards partially or totally inoperative after 15, 20 years of age. Multiple HPs and TIs of the time are still running quite strong.
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Offline Fungus

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #20 on: April 26, 2018, 05:06:31 am »
Dave, you rave about Casios and I grew up loving them as well, but in terms of durability they leave a lot to be desired.

There was a time when they were really good. I remember my FX-180P fondly.


After that they went downhill IMHO, especially the keyboards.

Multiple HPs and TIs of the time are still running quite strong.
I'm not a TI fan but HP made some good, solid, basic scientific calculators that have lasted. The calculators I use today are old HPs.

nb. I'm not a fan of graphing calculators in general, I only need a basic scientific model for what I do.

This thread is now doomed to turn into a flamewar.
« Last Edit: April 26, 2018, 05:23:41 am by Fungus »
 

Online rsjsouza

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #21 on: April 26, 2018, 05:49:38 am »
Dave, you rave about Casios and I grew up loving them as well, but in terms of durability they leave a lot to be desired.

There was a time when they were really good. I remember my FX-180P fondly.


After that they went downhill IMHO, especially the keyboards.
My units are older than this and their keyboards started to fail some 10~15 years ago... :(

Multiple HPs and TIs of the time are still running quite strong.
I'm not a TI fan but HP made some good, solid, basic scientific calculators that have lasted. The calculators I use today are old HPs.
To me the TI calculators of the 70's-80s still have good working condition keyboards (TI-30, a couple of TI-59s, a TI-66). I also have a pair of HP11Cs and HP48S and GX (well into the 90's) which are still pretty solid.

This thread is now doomed to turn into a flamewar.
:-DD :-DD :-DD
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Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Offline Fungus

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #22 on: April 26, 2018, 06:08:00 am »
There was a time when they were really good. I remember my FX-180P fondly.
My units are older than this and their keyboards started to fail some 10~15 years ago... :(
I'm not sure what happened to my FX180P. Lost in the mists of time somewhere.

To me the TI calculators of the 70's-80s still have good working condition keyboards (TI-30, a couple of TI-59s, a TI-66). I also have a pair of HP11Cs and HP48S and GX (well into the 90's) which are still pretty solid.
I've got the obligatory HP11C but I really like my HP 20S. It's not a famous model but it has all the right functions and layout for me. It does hex/dec/bin conversions with very little fuss. I don't know any other calculator which does those without half a dozen keypresses or you have to go into a special mode first.
 

Offline bjcuizon

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #23 on: April 26, 2018, 08:47:03 am »
Thats a thin as calculator right there. I just skipped a bit when Dave destroyed it   ::).
I also have something similar...its an "IMA" branded calculator, Model No. LC-684. Maybe late 1980's to 1990's era. It is also solar powered but its like 2mm thick so I think it still doesn't beat Daves one. ;D
Don't mess with an Electronics Engineer, it Megahertz!
 

Offline chickenHeadKnob

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #24 on: April 26, 2018, 11:21:03 am »

I've got the obligatory HP11C but I really like my HP 20S. It's not a famous model but it has all the right functions and layout for me. It does hex/dec/bin conversions with very little fuss. I don't know any other calculator which does those without half a dozen keypresses or you have to go into a special mode first.
Sharp EL-540d vintage approximately 1984, does conversions with 2 key presses. First press yellow shift key then select desired (->bin) (->hex) ect. Also has (AND) (OR) (NOT) (XOR) (XNOR). Not RPN or graphing or programmable but good and under appreciated. Last calculator I ever bought. I started out as  a calculator nerd teenager/young adult and then the urges slowly left me for good.

Here is a pic:https://www.ebay.com/itm/MINT-RARE-Sharp-EL-540D-Solar-Power-Scientific-Calculator-MANUAL-EL540-/162937868447
 

Offline Fungus

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #25 on: April 26, 2018, 03:12:38 pm »
Sharp EL-540d vintage approximately 1984, does conversions with 2 key presses. First press yellow shift key then select desired (->bin) (->hex) ect. Also has (AND) (OR) (NOT) (XOR) (XNOR). Not RPN or graphing or programmable but good and under appreciated. Last calculator I ever bought.

Yes, that's how easy it should be. I like the way the hex input keys are directly above the numbers, too.

You can get a mint condition one for $30, too!

Looking around on eBay: The easy hex/dec/bin feature seems common to a lot of Sharp calculators, even the fancy newer models. Who knew? I might have to look into them and see if there's a model for me. Your 520D doesn't have a backspace button though, and I like those...

My unfashionable HP has one other killer feature: It converts degrees<->radians with a single (shifted) keypress. All scientific calculators have degrees/radians modes but not many will convert angles between them.
« Last Edit: April 26, 2018, 10:10:33 pm by Fungus »
 

Online rsjsouza

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #26 on: April 26, 2018, 09:52:34 pm »
Interesting simple base conversion with the Sharp: even a newer model seems to be a two button operation.
http://www.sharp-world.com/products/calculators/sc_calculator/el-w531/index.html

I will investigate and see if it uses larger than 32-bit precision. The TI-89 I had was capped in 32-bit, thus sold it and ended up getting a modern HP35S which goes to 36-bit - still a good calculator, but the base conversion is not that straightforward (although finger memory does wonders). The other calculator I have (HP48) goes to 40-bit, but I leave it at home as I am afraido to lose it :P

From Sharp I remember drooling over their pocket computers PC-1211 and PC-1500 back in the 1980s.
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Offline rrinker

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #27 on: April 26, 2018, 11:34:11 pm »
 The Casio I used in college was much like that. It was the scientific one, forget the model number, with additonal keys on the fold out side. That was probably my all-time favorite calculator. It had all the common physical constants in it, plus it did logic, converted number bases between dec, hex, bin, and octal, converted between english and metric, and of course had all the requisite math and science functions. No graphing or programming, but didn't need that at the time. It was still my go-to years after graduation, until my first born decided to 'hide' it one day by putting it on top of a lamp where it wasn't immediately noticed, until the plastic had melted through and destroyed the secondary keyboard.
 I did learn how to use HP and their RPN, because if your calculator broke down in the midst of an exam, our one professor was all too happy to lend you one of his - except they were all HPs. I know more than one classmate got caught out by this. But my Casio never failed. It took a 75 watt light bulb to kill it.
 I remember those Sharp pocket computers (mostly from Radio Shack, not the original Sharp versions), but the one I actually had, the Radio Shack PC-4, was actually a Casio as well. I wish I had found it when cleaning out my Mom's house, but I must have lost it in a move long ago. The neatest thing I did with it was utilize the cassette motor control relay to drive a bigger relay  in a box full of D cell batteries to launch model rockets. They always look better if you can stand way back, but the stock launch controllers only had maybe a 20 foot cord, plus it used AA batteries which gave you maybe half a dozen launches. With my controller box plus a program in my pocket computer, my friend and I could BOTH stand back and watch.

 I have to say, kind of a shame to see this one destroyed, but it is also interesting to see how they pulled it off. More amazing when you consider when it was made. A calculator that thin would still be a marvel today. And to be made so cheaply it could be used for business promos. 
 

Offline Fungus

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #28 on: April 27, 2018, 08:02:37 pm »
A calculator that thin would still be a marvel today.
You can see there's no magic inside it, but actually doing it 0.8 mm thick takes some stubbornness.

I think they were mostly doing it to show off, not because it was necessary. If you look at Japanese calculators back then there's a whole load of them that were just trying to be the smallest, thinnest, most functions in a watch, etc.

eg.

(gotta love the gold bling finish)

And to be made so cheaply it could be used for business promos.

And also made to last by the looks of it - there's a layer of steel on front and back!

« Last Edit: April 27, 2018, 08:26:54 pm by Fungus »
 

Offline MT

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #29 on: April 28, 2018, 02:34:46 am »
Regarding the buttons:

Wouldn't the resistance change with pressure even if the carbon pads were always touching?
Maybe they work by looking for changes in resistance.

Yes it does, with all carbon/graphene pill key switching instead of logic sensing your matrix let a ADC sensing
the matrix. It's set up with velocity threshold points, works well with and without separator. Every sampling
boom box have done this for decades. Its called velocity sensing. If you quickly want a matrix keybed for your
projects buy a B9 pencil and plain paper then draw them out. I tested this back in the day with a HB class pen
recall mine did easily thousands of finger hits without wearing out. Or buy some conductive ink/paint, or
make your own.
« Last Edit: April 28, 2018, 02:47:44 am by MT »
 

Offline Fionn

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #30 on: November 27, 2018, 02:47:19 am »
Just watched and found this text at 24:55 (in attachment)
What could it be?
 

Offline amyk

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Re: EEVblog #1078 - World's Thinnest Calculator Teardown
« Reply #31 on: November 27, 2018, 01:48:06 pm »
It's very likely the IC was made by NEC, possibly even just the bare-die version of the same one as in these:

http://www.vintagecalculators.com/html/casio_mini_card_lc-78.html

How do these compare? Are they thicker but could actually be made thinner (and are not, because they would be too fragile?)

https://www.aliexpress.com/item/New-Portable-Ultra-Thin-Mini-Calculator-8-Digit-Credit-Card-Sized-Solar-Powered-Pocket-Calculator-Black/32819834728.html

(there are similar ones if you just search "ultra thin calculator", all at <$1 each.)
 


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