LCDs on HP Calculators before the 41C


Does anyone know if HP used LCDs on any calculators before the 41C? I remember in College Chem class in 1982 that someone had an HP that was not a 41C that had an LCD. I want to say it was like a 32E/C or 33. Can anyone shed some light on this?



The next LCD calculators were the voyagers, the HP-11c and HP-12c were the first two, followed by the 10c and then 15c and 16c.

The HP-31E, 32E, 33E, 33C, 34C, 37E, 38E, and 38C all used red led displays.

The HP-41c was HP's first!




after reading and seen so many things about unreleased models - like the HP95C and the X-Pander - I wonder if Richard did not have the chance to see some stuff like these. If you have a look at Craig Finset's database you'll see some entries related to never-seen or never-released models, something like a rumor.

Even TI had its unreleased famous TI-88, and a few units are available somewhere. Collectors' pieces, indeed.

Pioneers second Voyagers after 1987, and the HP32S is the closest HP41-look model, but it was not available in 1982.

Now I'm curious, too.

Luiz C. Vieira - brazil


Pardon the ignorance, but what do you mean by 'voyagers'?

I noticed another thread that used that term. Thanks for any info?



Hi Joe,

Voyagers are a series of calculators made during the 1980's. They are:

HP-10C, HP-11C and HP-15C scientific

HP-12C financial (22 years old and still manufactured!)

HP-16C programmer's calculator

Details are available elsewhere on this site. The nice things about these machines are that they are very solidly build, fit neatly in a shirt pocket and run almost forever on silver oxide batteries.

Maybe some of us are feeling nostalgic if we feel that HP could solve half of its calculator woes if it brought back some of these very desirable machines (particularly the 11 or 15).

I have an 11C and a 16C and I'm never ever giving them up! (I just got a 48GX, though, and that one's pretty cool, too.)

- Michael


Thank you Michael for the reply.

I have been bitten by the 'bug'! I have a 12C right now that I am very happy with.

I am 'searching' for a 16C. I think that would be a nice addition.

In my opinion the holy grail of HP's is the 67. I remember when I was a teenager, some of my dad's fellow engineers had HP67's and I used to drool over those machines! I'm amazed they still fetch the prices they do on Ebay.

Thanks again!


I vote that the guy in the college class in 1982
probably had an HP-34C . Nice rig.
It took 2nd place to the HP-41C most of the time,
but either was popular then.


Why celebrate LCD's over LED's.

If you have enough battery oomph to keep it going,
the LED's looked WAY COOLER than the LCD .

LCD is dull grey and boring.
LED was brilliant, sizzling, crisp,
and if the power went off in the building,
you could punch in all 8's and use it for a

If HP was "into it" anymore they'd give you some
display options that sizzle with much more luster
than a dull drab LCD.


LCD works better in bright light but calculators are used where the light isn't too bright. So LED looks better. I used the 9825B for a while and it has full dot matrix 32 character LED display. It looks great but after a few nights on the thing I started seeing cyan in the morning.


I'm waiting to see who uses the new organic LEDs (OLED) first in calculators. Kodak licensed the manufacturing to a firm in Taiwan some time ago. IBM likes to show off OLED displays in concept watches and color OLEDs are in the works.

So LEDs are back, though based on some jellyfish chemophore this time (that's where the "organic" comes from).


Hello, Masao;

do you know where to find OR do you already know the specs for these organic LED's? The only information I have is that blue-light LED's exist because of this technology. I read about blue, cyan LED's since the 80's, and now they are indeed available. The active pannel in some new laptops use this sort of technology, right?

If you know any links to any e-docs about it, I'd appreciate knowing about them, too.

Thank you.

Luiz C. Vieira - Brazil


Hi Luiz,

OLEDs are quite new. I don't think anything from the 1980s would pertain to them. One of the first showcase for OLEDs was the display that you could roll up. I think those are supposed to go on the market soon (if not already?). I remember reading _quite_ a while back that the first drivers for using OLEDs as displays were ready. At that time one set was shipping and the other about to ship.

IIRC, OLEDs use less power and emit their own light, i.e., the energy hungry backlight is no longer necessary.

Try googling around the blue nowhere. There's lots of information out there.

After I made the earlier post, I started wondering how Kinpo would ration out something like this. Judging from their Web site, Citizen seems to be their model partner. And of course, Kinpo makes calculators for Texas Instruments! So how does HP fit into their scheme of things, I wonder, for such new technology?

Mosk as in Tosk (Star Trek Deep Space Nine)
Knights of Access (Jeffery Deaver's "The Blue Nowhere")


I meant to say -
IIRC, OLEDs use less power ***THAN LCDs*** and emit their own light, i.e., the energy hungry backlight is no longer necessary.

I think these are a couple of reasons why IBM is so interested in showing them in watches, where battery technology has been a big limiting factor. Maybe Citizen will eventually use them in their SPOT watch, since IBM and Citizen are (were?) working together on a WatchPad.


Hi, Norm;

here we are dealling with mixed, not EXACTLY analog matters.

Since the first LCD I saw I realized they could be used and read under direct sunlight, something impossible to be done with LED displays. I remember surveyors gladly ran from the HP67 to the HP41C simply because they could use it under sunlight. I remember a classmate told me once: hat is it using a calculator in the dark good for if you can barely see the keyboard and even take notes or read anything? If there is energy to charge batteries, then turn the lights on! I like reading and studying under fair light, better if (not directly) under sunlight. It's a lot easier to read, to write. I don't like studying and working with poor light. And in this case, there should be light enough to see LCD's characters and key inscriptions and notebooks and books...

In other hand, I use LED anytime I need to signal anything in a pannel. My first digital multimeter was a home-buitl based on the famous CA3161/3162. I remember I had to change power supply design because measurements were unstable and I used a regulated +5VCC to the IC's supply and a non-regulated +6Vcc to the LED's line... Hey, wrong place to talk about this. Sorry, guys... Anyway, it still works but today I use a portable, LCD reading mulimeter.

Jus my thoughts.

Best regards.

Luiz C. Vieira - Brazil


For my HP 67, I had one of those sunshades not unlike the scope Mr. Spock would look into at his science station onboard the United StarShip Enterprise (Star Trek The Original Series). It snapped on and off with ease.

I also used it during exams, since the 67's LEDs were designed to be seen from different angles, i.e., real world tool. The LEDs on my HP 21* and HP 25 were sunk deep into the calculator (for exams?). Don't get me wrong, I really liked my HP 25 (but I really wanted a card reader, since keying in the programs every time was so tedious and I really wanted the HP 65 in the first place). I gave the 25 to my oldest sister when I got my 67.

*It was really my father's HP 21.


Mostly for low power consumption. And for alphanumeric displays, redefinable fonts and graphing, I've never seen an LED display that could match the LCD displays. LEDs are hard to read in bright sunlight, and I remember that red LEDs were hard to make sense of under the red lights on a ship.

Still, under the right conditions and for the right uses, they do look very nice and are easy to read. So if they ever get the power consumption down to something comparable to an LCD display, I'd welcome a new calculator with an LED display.



Wow, did this thread get off track. All I was looking for was information for any HP calculator that had an LCD before the 41C. What I saw in 1982 was an HP of the old 30 series that had an LCD. The only reasoning I can come up with so far is:

A) it was a prototype that was being tested. The question there would be how did a prototype like that find its way to a student in a 2 year college in northeast Texas.

B) it was an actual 30 series something that was built at the end of the production run and a compatable LCD was put in instead of ordering more LEDs to finish the last few units on the line.

This question has always been in the back of my mind and it comes to the surface from time to time just to taunt me to look some more.



James wrote:

Still, under the right conditions and for the right uses, they do look very nice and are easy to read. So if they ever get the power consumption down to something comparable to an LCD display, I'd welcome a new calculator with an LED display.

The three problems with old LED calculators are:

* Batteries

* Power-guzzling LEDs

* Power-guzzling ICs

all of which contribute to short battery life.

But the state of the art has advanced over the last 25 years and makes LED calculators much more attractive now.


Other threads here compare the old Nicads to new Nicads and NiMHs which could give increased operating time. A problem is that the old calcs were not designed with the new batteries in mind. This leads to questions about charging time, waveforms, etc.

But suppose we were to design a new machine with modern batteries and power supply circuitry. All the technology now used in portable computers and cell phones could be applied to calculators. This includes NiMH and Li-Ion batteries, quick-charge circuits and high-efficiency DC-DC converters. This is all off-the-shelf stuff.

An extra benefit is that with modern circuitry we wouldn't have to worry about frying the calculator's little innards if the battery pack were removed.


New LED materials are much more efficient than their 1970's counterparts. I've been looking at some Agilent data sheets and it looks as if seven-segment displays using AlGaAs would require only 1/5 the power of the old so-called "high-efficiency" Red LEDs. We don't have to rely on new, unproven technologies like Organic LEDs.

The old small "stick" LEDs used in calculators are no longer manufactored, so an LED manufacturer would have to design new displays and tool up.

If somewhat higher power consumption could be tolerated, we could even envision other colors. Blue LEDs, anyone?


The old PMOS ICs used in the early calculators had pretty high power consumption. CMOS circuits operated at a reasonable clock rate would consume essentially zero power. Witness the Voyagers, which have been known to run for over a decade on their original batteries.

So maybe the time is right for a new generation of LED calculators. My vote is for a 26th Anniversary Edition HP-29C. Perhaps the R&D and manufacturing cost could be justified by making the first run a limited-edition deluxe collectable. Ebay prices seem to justify the idea that under the right circumstances, people will buy high-quality calculators for high prices. Heck, even I'd buy one or two! (And maybe lower cost units could follow.)

- Michael



it's time to think of actual replacements for Woodstocks and Spice's (among others) LED displays. Should industry care for building LED displays as building blocks, like thos found in HP Classic models? I have at least four woodstock LED displays with corroded digits that no longer work. Even if they are orange or blue (not green because of the red protective "shield") I think that digit's size would be greatly welcome.

Any specs about these? Any link to be consulted?

Thanks for any information.

Best regards.

Luiz C. Vieira - Brazil


What about using an OLED (organic LED) display? I have a Motorola cell phone with this type display. Advantages are VERY bright, vivid color display, low power consumption. I understand they are still having problems creating laptop size displays (production techniques still being developed), but a calculator display is similar in size to the cell phone.


Hello, Layne;

OLED's are the subject, indeed. I was not aware of them as commercial products since this post written by Masao Kinoshita. And I'm willing to know how are 7-segments being packed, i.e., dimensions, size, specs, colors... If OLED's use less current than LCD's, they have a much higher internal resistence. Would existing, already designed LED drivers deal with OLED's as well? I'm asking about this because scan frequency in multiplexed drivers take into account the final brightness and energy transfered to the LED display. Should pulse width and peak values be changed if OLED's are used instead of LED's when keeping existing electronics?

If so, I'll have to research before thinking about using new OLED's in vintage HP calculators. Hey, operation time with fully charged batteries would be increased in about 3 times! It worth trying something about it...

Hey, Norm, any ideas? Usggestions? Comments? Anyone else?

Best regards.

luiz C. Vieira - Brazil


OLED's do look attractive. But as I look at it I guess I see it more as a replacement for LCD's in graphic calculators rather than as the basis for a retro LED machine.

Worth keeping an eye on, though.

- Michael


Hi Luiz,

I've looked all over the place and it looks like NO ONE is manufacturing the small multidigit LED displays used in calculators. The closest I could find were some multicharacter intelligent alphanumeric LED displays from Agilent. But these are not compatible with calculator displays.

I guess when LCD's came in, nobody was interested in the small LED's anymore. It's too bad.

- Michael



I proposed this long ago, but maybe time has come to suggest it again:

--- snip ---

"Another project that might be worthwhile in that vein is the matter of the "Classic" displays. They rely on an obsolete and hard-to-find five-digit seven-segment LED. Matched brightness on the three sets of five-digit displays are tough. BUT... A project to make a "drop-in" replacement for the display... a circuit-card with fifteen matched LED digits, is possible, if enough people want to do this. Single LED digits are easy to source, in many sizes. Design could probably proceed NOW."

--- snip ---

(from Archive 3, Aug 24 2000 "A modest proposal", one of many ideas tossed off in a rather long essay)

Basically, there ARE things out there to be done, either as a group, or by some entrepreneur-type who wants to supply to a market that is waiting.

The HP LEDs were actually rather small-charactered, but such was the state of the art back then; they made up for the tiny segments by encasing them behind clear epoxy lenses (one over each seven-segment character; this lent them a nice look head-on, and I believe made viewing them at an angle a bit easier, too-- but experimentation could tell you if an "unlensed" LED, maybe set a bit more forward in the case, would lead to increased readability. Character size itself might be a bit tweakable, too... all of that being behind the red bezel, you'd probably have to have two Classics side by side to tell the display was not an "original".

As Classics become more and more a collectible than a commodity, perhaps being as faithful to the original as possible is necessary. In which case, a molded clear styrene strip of "bubbles" might be worth attaching to small-segment arrays, for that authentic "HP" look. Cost of casting the bubble strips from Lucite would be nearly negligible, a "garage" operation. A rubber mold, a mild vacuum chamber to keep air pockets down, and resin two-part that you can acquire at most hobby chains. Even omit the vacuum if you don't mind a few spoilt strips due to air-resin mixing.

In short, Luiz, a bit of parts research would LIKELY get you closer to building "stick"s for yourself and others out of single character elements, and it seems to me that a run of fifty or so would prolly meet with an audience in Here.

Fifty assemblies would be large enough that you would be able to sort the elements out of those 750 singles sent you by a place like DigiKey by comparative brightness, so that all 15 in each calc's display would be pretty darn close to each other. If you do less than this, you need to have a supplier willing to sell you pieces sorted by codes from the production run. HP used to have letter codes characterizing brightness, and some LED manufacturers sort them out this way per tray.

(By the way--- regarding OLEDs--- they are a REAL technology now, not the vaporware they were when I was writing about us building our own design calculator two and a half years ago. At this moment, few facilities pump out OLED displays yet, and the concentration has been on dot-matrix arrays for PDAs etc., but that will likely change and some off-the-shelf small alphanumeric stuff is likely to appear in the next two years or so. Uniax (sold to Dupont Displays, look these guys up) was a developer of the "flexible" tech mentioned earlier in this thread, and the key there was that OLED could be PRINTED or silk-screened as part of a mylar sandwich, and thus it was very thin, dissipated its low but "age-producing" heat very well, and could be tooled up into unique designs incredibly cheaply; it was just printing, after all. I am a firm believer in OLED, and feel its color can be fairly well "tuned" to provide good readability even in bright light (not limited to reds, OLEDs make nifty greens and others too). My own preference is an amber-yellow on flat black, accomplished by shining the element through a fine mesh screen of black polyester. The contrast is incredible, and easy on eyes as well. If I ever DO design my own calc....)

Well, best of luck to all!


Hi Glynn!

Last night I looked around at LEDs to see what small displays are available. I looked in several distributor catalogs, all of Agilent's LED Web pages, and many other Web sites. What I found is not encouraging.

First, as I mentioned somewhere, the old multidigit LED "stick" displays don't seem to be available as new parts from anyone. Apparently customers lost interest when LCDs became widely available. The only way to get stick displays is to salvage them from existing equipment. (Keep in mind that there were many different types, so buying an old cheapie TI to replace HP LEDs isn't going to fly.)

I've looked around for small single-digit LEDs. The smallest I found had digits 0.2" high, a little bigger than calculator displays. One vendor is SunLED: see
for a typical unit. It is 0.394" high X 0.272" wide. Twelve of these in a row would be 3.264" wide total. This is even wider than my 48GX! A display made of these would not fit into any pocket calculator I know of. And this was the smallest single digit part I found.

Agilent does make small multicharacter LED displays; these are small enough to (perhaps) fit into existing calculators. One of the smaller ones is the HPDL-1414 4-character display, see These devices would not be electrically compatible with existing calculators (though they could serve as the basis for a newly-designed calculator).

I suppose it would be possible to go to an LED manufacturer and get custom units done. Would it even be feasible, given the high engineering, tooling, and minimum order requirements? (This question would also apply to OLEDs when the right types appear. The chances of an off-the shelf part being exactly what we need would be small.)

This has been a very interesting discussion. I read the old thread, including your post, and I was impressed. An open-source calculator would be a worthwhile project if enough people got on board. I would be willing to share my thoughts on this if you are willing.

- Michael

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