Question to HP-35 owners

[Willy R. Kunz]

In 1973, I traded my HP-35 for a HP-45. So when I created RPN-35 SD, the HP-35 simulator for iPhone, I verified its correct operation against a microcode-based emulator.

There is one point I'm unsure of, though: the lighting of decimal points in a low-battery situation. HP's Operating Manual states on page 23: "All decimal points but one light in the display when 2 to 5 minutes of operation time remain." [Emphasis mine]. Accordingly, the picture below the text shows no decimal point in the first digit of the fractional part.

However, on page 28, they say: "All decimal points light to warn you that you have a few minutes of operating time left."

So, the question is: how does a v3 or v4 HP-35 really behave? And if page 23 is correct, which decimal point does remain unlit?

[walter b]

P. 23 is correct. And the decimal points are inverted, i.e. the one which should be lit isn't while all other are.

d:-)

[Willy R. Kunz]

(01-31-2015 02:12 PM)walter b Wrote:  P. 23 is correct. And the decimal points are inverted, i.e. the one which should be lit isn't while all other are.

d:-)

Thank you for the quick answer. Interestingly, the German manual states that 14 decimal points are lit (out of 15), but later claims all are lit.
At any rate, this would mean that the illustration on page 23 is not correct (see attachment.) Clearly, the actual decimal point is lit. From an electronics standpoint your answer makes a lot of sense, of course.

[Thomas Radtke]

The illustration is correct (at least for my 35).

[Willy R. Kunz]

(01-31-2015 04:19 PM)Thomas Radtke Wrote:  The illustration is correct (at least for my 35).

Now I'm really confused. Are the decimal points inverted, as Walter B. wrote, or does a seemingly arbitrary decimal point remain unlit, as HP's illustration implies? If the latter is true, what are the rules? What happens if you multiply the number in the picture by 10? Does the decimal point of the digit "3" get unlit (see attachment)? Do different versions of the HP-35 behave differently?

If any HP-35 owner has the final answer, I'd be glad to hear it. Otherwise I'll provide the method described by Walter B in the next update of RPN-35 SD. It makes a lot of sense as it is very easy to implement in hardware.

[Thomas Radtke]

The batteries are low when extra decimal points are displayed.

http://www.hpmuseum.org/batts/battery.htm

Don't know of any variations.

[MarkHaysHarris777]

Now then, how many of you remember saving battery life with your real HP35 (or 45) by pressing just the 'decimal point' so that 'only' one led point would be drawing power ?

[BarryMead]

(02-02-2015 08:33 PM)MarkHaysHarris777 Wrote:  Now then, how many of you remember saving battery life with your real HP35 (or 45) by pressing just the 'decimal point' so that 'only' one led point would be drawing power ?

I still have my original HP-35. I recently bought a new NiMH battery and a USB charging cable for it so
it even works on battery power again.

[MarkHaysHarris777]

(02-03-2015 01:08 AM)BarryMead Wrote:  

(02-02-2015 08:33 PM)MarkHaysHarris777 Wrote:  Now then, how many of you remember saving battery life with your real HP35 (or 45) by pressing just the 'decimal point' so that 'only' one led point would be drawing power ?

I still have my original HP-35. I recently bought a new NiMH battery and a USB charging cable for it so
it even works on battery power again.

~nice! Keep that baby... wish I still had mine!

[Willy R. Kunz]

(02-03-2015 01:08 AM)BarryMead Wrote:  I still have my original HP-35. I recently bought a new NiMH battery and a USB charging cable for it so
it even works on battery power again.

Alright, then, you might be the right person to come up with the final answer to the question this thread is all about: which decimal points are lit when the battery charge drops below a certain level? Do they just invert, as WalterB suggests? Or do they show up in the way the HP-35 manual states (see attachment)?

One more question: if you plug in the power adapter, does the battery warning disappear immediately, or only when the battery charge crosses the trigger level again?

My guess is that HP chose a simple hardware solution: XORing the decimal point signal with the output of the voltage detector. No software involved at all.

I'd love to make my HP-35 simulator behave like the real thing.

[PANAMATIK]

(02-07-2015 08:52 PM)Willy R. Kunz Wrote:  Alright, then, you might be the right person to come up with the final answer to the question this thread is all about: which decimal points are lit when the battery charge drops below a certain level? Do they just invert, as WalterB suggests? Or do they show up in the way the HP-35 manual states (see attachment)?

One more question: if you plug in the power adapter, does the battery warning disappear immediately, or only when the battery charge crosses the trigger level again?

My guess is that HP chose a simple hardware solution: XORing the decimal point signal with the output of the voltage detector. No software involved at all.

I'd love to make my HP-35 simulator behave like the real thing.

Hello Willy,

I plugged my HP-35 SNr 1143S to my power supply with variable Voltage output. The level where the dots come up is about 3,65V. The nominal Voltage is 3,75V. If I reduce the voltage the dots slowly appear, some of them earlier than others, but within about 50 mV below the threshold all of them are there.

To my surprise it does neither inverting the decimal dots nor it does show all decimal dots. It shows all dots except the one following the original numbers decimal dot. The original dot is not inverted. if you press CLX you see .0. ........... . (The last dot is the punctuation mark). If you press any key while in low battery mode, the invisible dot will be shown for 100 ms, then vanishes again.

You don't need to press a button for showing the low battery signal, it appears as the voltage drops, other than the HP-25, where you need to press a button for sampling the battery voltage.

I cannot tell you whether all versions of HP-35 show the same behaviour. My HP-35 version doesn't show HP-35 on its front label, only the name Hewlett Packard.

The HP-35 manual is also right, it shows exactly at number 2 the dot is missing, that is one digit right of the decimal dot.

Bernhard

[Willy R. Kunz]

(02-07-2015 09:47 PM)PANAMATIK Wrote:  

(02-07-2015 08:52 PM)Willy R. Kunz Wrote:  Alright, then, you might be the right person to come up with the final answer to the question this thread is all about: which decimal points are lit when the battery charge drops below a certain level? Do they just invert, as WalterB suggests? Or do they show up in the way the HP-35 manual states (see attachment)?

One more question: if you plug in the power adapter, does the battery warning disappear immediately, or only when the battery charge crosses the trigger level again?

My guess is that HP chose a simple hardware solution: XORing the decimal point signal with the output of the voltage detector. No software involved at all.

I'd love to make my HP-35 simulator behave like the real thing.

Hello Willy,

I plugged my HP-35 SNr 1143S to my power supply with variable Voltage output. The level where the dots come up is about 3,65V. The nominal Voltage is 3,75V. If I reduce the voltage the dots slowly appear, some of them earlier than others, but within about 50 mV below the threshold all of them are there.

To my surprise it does neither inverting the decimal dots nor it does show all decimal dots. It shows all dots except the one following the original numbers decimal dot. The original dot is not inverted. if you press CLX you see .0. ........... . (The last dot is the punctuation mark). If you press any key while in low battery mode, the invisible dot will be shown for 100 ms, then vanishes again.

You don't need to press a button for showing the low battery signal, it appears as the voltage drops, other than the HP-25, where you need to press a button for sampling the battery voltage.

I cannot tell you whether all versions of HP-35 show the same behaviour. My HP-35 version doesn't show HP-35 on its front label, only the name Hewlett Packard.

The HP-35 manual is also right, it shows exactly at number 2 the dot is missing, that is one digit right of the decimal dot.

Bernhard

Wow. Great answer, thank you so much.
So you have a version 1 or 2 HP-35, depending on whether you see the red dot or not. And the manual's illustration is correct, not the statement on page 28! Very surprising, to put it mildly.
Well, then, a nice software challenge. Totally irrelevant, but fun.

Willy

-- Dem Inscheniör ist nichts zu schwör.

[PANAMATIK]

(02-08-2015 11:13 AM)Willy R. Kunz Wrote:  So you have a version 1 or 2 HP-35, depending on whether you see the red dot or not.

Unfortunately I cannot see a red dot.

I want to mention, of course the dot inside the 0 after the CLX is also on:
.0. ........... , but cannot be expressed with ASCII characters.

Bernhard

[Dieter]

(02-08-2015 06:10 PM)PANAMATIK Wrote:  

(02-08-2015 11:13 AM)Willy R. Kunz Wrote:  So you have a version 1 or 2 HP-35, depending on whether you see the red dot or not.

Unfortunately I cannot see a red dot.

Just to be sure: that red dot is not in the display. ;-)

(02-08-2015 06:10 PM)PANAMATIK Wrote:  I want to mention, of course the dot inside the 0 after the CLX is also on:
.0. ........... , but cannot be expressed with ASCII characters.

This forum supports Unicode. On a Windows system you can enter a central dot by pressing Alt+0183 (hold down the Alt key while typing the 0183 with your other hand). Did you mean something like this?

· 0 ·   · · · · · · · · · ·

Dieter

[Mark Hardman]

(02-08-2015 06:46 PM)Dieter Wrote:  

(02-08-2015 06:10 PM)PANAMATIK Wrote:  I want to mention, of course the dot inside the 0 after the CLX is also on:
.0. ........... , but cannot be expressed with ASCII characters.

This forum supports Unicode. On a Windows system you can enter a central dot by pressing Alt+0183 (hold down the Alt key while typing the 0183 with your other hand). Did you mean something like this?

· 0 ·   · · · · · · · · · ·

Dieter

· ʘ ·   · · · · · · · · · ·

[Thomas Klemm]

(02-08-2015 11:13 AM)Willy R. Kunz Wrote:  -- Dem Inscheniör ist nichts zu schwör.

[PANAMATIK]

(02-08-2015 06:53 PM)Mark Hardman Wrote:  · ʘ ·   · · · · · · · · · ·

Nearly perfect, but HP-35 has 15 digits

·  ·   · · · · · · · · · · ·

[Willy R. Kunz]

(02-09-2015 02:36 AM)PANAMATIK Wrote:  

(02-08-2015 06:53 PM)Mark Hardman Wrote:  · ʘ ·   · · · · · · · · · ·

Nearly perfect, but HP-35 has 15 digits

·  ·   · · · · · · · · · · ·

Time to reveal a peek preview of the next version of RPN-35 SD (see attachment.)
And yes, when you tap a key, the unlit decimal point appears for 100 ms.

[Willy R. Kunz]

(02-08-2015 06:55 PM)Thomas Klemm Wrote:  

(02-08-2015 11:13 AM)Willy R. Kunz Wrote:  -- Dem Inscheniör ist nichts zu schwör.

:-)))
Great find! This also confirms that the correct spelling is "Inscheniör", not "Inschenör".

[PANAMATIK]

(02-09-2015 09:08 AM)Willy R. Kunz Wrote:  Time to reveal a peek preview of the next version of RPN-35 SD (see attachment.)
And yes, when you tap a key, the unlit decimal point appears for 100 ms.

Do you want to show the dots when the iPhone batteries are low? In the HP manual is written, that you will have 2 to 5 minutes left, after the dots appear, and using the calculator beyond this time may result in wrong answers - quite a challenge.

Bernhard