HP Classic with new electronics (a la uCalc/uWatch?)


I love the uCalc and will certainly order one when it's ready (my inner geek wants the uWatch, too, but I know I wouldn't wear it...).

I'm in a frenzy of HP Classic restoration right now and it occurred to me that it would be *quite* easy to make a uCalc/uWatch PCB that replaces a Classic CPU board and then it would be possible to have a fully custom/open source calc that used the incomparable Classic keyboard, form-factor and, yes, warm LED glow - for desktop use mainly.

(I'm back to using Classics for all my daily calc-ing and just loving the user interface...).

Is that too abhorrent to the HP faithful? Or kinda cool? Who wants one? Which classic to base it on?


There are lots of dead Woodstocks, one of them not far away from me ;-(. If anyone sells a repairing kit, I'll certainly buy one.

Edited: 16 Dec 2009, 5:40 p.m.


This was discussed this some time back in terms of using a new platform HP, like the 35S or 12C casing. With a drop-in PCB and LCD replacement, or possibly even a 7 segment LED display.

Just like the uWatch and uCalc, I like something novel, so for me it would be a nice LED display :)

I don't know about using an old casing that aren't readily available, as you'd be painting yourself into a supply corner there.

But for me such a project is down the list, uCalc first as a warm-up, then the perpetual uWatch2.



Yes, I agree your efforts should ideally be focused on uCalc right now!

And good point about the supply issue - I'm sitting on multiple 45s and could easily see myself converting one :-)

I'm also an electronics buff, so possibility of me and others helping with a hardware port in the future is not out of the question...

But first things first! Keep up the great effort. Let us know if we can help.




There used to be site discussing a project to recreate the HP-41C CPU board with modern electronics. I can't find the link. Someone else?


In this thread, starting with message #3:
Board for Newt CPU


I was musing more on why to do this, occurred to me that a 55C might be very nice ;-)


HP 15C with LED display :


HP 15C with LED display :
That will take a big battery. Where does it go? A coin cell definitely won't do it.


I"m finding that having a lovely red LED glow from my Classics works just fine on my desk since plugging in is just not a problem, well worth it! And my office gets dark in the evenings, so the LEDs are much more visible.

I see some modern watches that have an LCD display and a bright backlight (red) that actually looks almost like LEDs - so I suppose it might be possible to have an LCD that is low power in good light, and brightly back-lit in poor light, and with the visual appeal of LEDs??


HP 15C with LED display :
That will take a big battery. Where does it go? A coin cell definitely won't do it.

Geoff doesn't show us his prototype is 5"x3"x1" ;)

Most "pocket" calculator images are taken under an angle you can't see its extension in the third dimension properly. Think of the conical shapes of the Classics etc. Compare an ad of the 19C with the original shape: Such pictures have a long tradition.




Where are the so necessary indicators? USER, GRAD/RAD, C, f & g...

It is really good looking, but I still like LCD´s. People claim that one can read LED-based displays in the dark easily... OK, and what else? Memorize the keyboard? I´m sorry again, but... what then? Would you take a note, look at something else, use the information, locate yourself... in the dark?

I never found any significant use for a calculator in the dark. A torch, perhaps... maybe to lighten up the place so the calculator can be used accordingly. But then... LED´s are no longer necessary.

I remember how hard it was to use LED-based instrumentation in the field. Batteries discharging too fast, the need of creating a shadow with the hand to see the numbers, heavier/larger equipments to hold high-capacity batteries... LCD´s removed these three problems at once.

And let´s face it: Voyager´s digits shape is one of the best.: good looking, easy to use.

My points, only.



Edited: 18 Dec 2009, 6:39 a.m.



You're missing the point. It's LLLLEEEEEDDDDDDDDDD's, baby! Have a great weekend!!!


LOL, yes it's all about the LEDs! Yesterday a 20-something kid in my office spotted my 1972 HP-80 on my desk and couldn't believe an LED calc! He loved it! Some things are just meant to be...

Here's an example of the LCD/fake LED tech being put into some watches (note all the little flags etc. so that HP-15C-types display can work, too...


Well for watches the true LED for me; versus OLED as pictured above, although I did purchase the First Fossil OLED watch. I find the display rather disappointing.

The collection has grown as these get restored but I do like the LED watch:

As far as night viewing goes, the HP-01 is my cockpits, lowlight environment (actually daytime and nightime). Especially with the raised tactile buttons that allow a simple memorization of key mapping. The display is bright and RED allowing for no disruption of night vision adaptation; a requirement in the South Pacific flights with no full moon. Radar returns do not show icing or ice crystals so running with the cockpit lights off and the background lighting on low is imperative at night for cloud avoidance.

I use the HP42S for my cockpit as it is slimmer then the 41CX (my favourite LCD calculator) but at night I need to shine a map light on the display. The HP-67 however does not need a map light and with my programs mapped to the top 5 buttons I have access again to a simple memorization of key mapping.

As far as the HP-15C LED version, well using an alpha/numeric display such as in the 9825a, increased memory, a timer/clock function it was done for fun 8-)

However, my favourite creation would be an OLED backlit:

-  a colored alpha numeric two line OLED display (backlit ability)
- increased memory and speed
- a dynamic timer/clock/beep(alarm) function
- 15C physical format
- USB facility

Excuse the colour choices, but a two line HP42S display with alpha on a similar menu type would be good.

Enjoy but don't stare at the OLED display too long




Nobody remembers my fonts... <8^(

Looks great to me... If you allow me to, I tried this look, with lower brightness.


Luiz (Brazil)

Edited: 18 Dec 2009, 4:06 p.m.


thats better and the fonts are excellent.

Now residing on my computer!

Cheers, Geoff



Hi Geoff, guys;

a couple of years ago I also draw this HP50G keyboard TTF. There is also this PDF file with explanations.

I was invited then to talk about the HP50G at a state university and I could not find a suitable, publicly available font for the HP50G keyboard. So I draw it and used with the other ones to build a presentation about it. I think it looked OK, will find it and post a link about it.

In time: have you, the lucky 'MoHPC DVD set' buyers, had a look at the 'Voyagers in Brief'? I know that there are some corrections to be made, mostly noted in the small, 12-page PDF I posted about it a couple of months ago. Since nobody mentioned anything about it, neither through e-mail, I decided to ask. Please, feel free telling me anything about it. I intend going ahead with the 2nd. Edition and fill the gaps that were left there.


Luiz (Brazil)


Seems that's exactly the display for Segal's Love Story, isn't it?


Hi Geoff,

I doubt I'm worth a subject ;) Anyway, you're missing the point for you're still not showing the 3rd dimension. I bet your LED 15C carries a 1" rucksack for the batteries, though needing a swap every 2 hours of operation. You should call it a 15SC since it will feature a semi-continuous memory with the LEDs taking all the energy. But you're right, it will serve well as short-time flash light in a cockpit a 2 a.m. over Tuvalu ;) Enjoy!


Killjoy. Maybe one of those super-thin rechargeable lithium cells could fit in the back, like the ones in cell phones. With mAH ratings that they get these days, I'll bet it'd run the led's for 10-12 hours on a charge!


I was comparing my cell phone battery to a TI-58 battery recently, and noted it had the same voltage, about twice the capacity and was about 1/4 of the volume.


Unfortunately, a different charger would be necessary.

I wonder why HP never had a 'standby' function that simply switches off the LEDs. Would have been great in non-'C' programmable models.


I wonder why HP never had a 'standby' function that simply switches off the LEDs

The closest that I (and I suspect, many others here) came was to start a number entry with just a period - and leave it that way while we figured out what to do next.


Turns out I don't have any 3 demensional views of the voyagers!

Cheers, Geoff

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