HP 15C and 15C LE not the same dimensions?



#2

not sure if this has been raised before but...

i just received my 15C LE, and i was struck by the fact that it is a smidge larger in all three dimensions than my circa 1984 15C. (most notable to me was that it felt thick in my hand before even comparing the two units side by side)

no time for a full review right now, but i'm unsure how i feel about the keyboard. i see why some might like it, but it's not the same as my old 15C nor an older 12C i also own. it will take some getting used to.


#3

Quote:
I just received my 15C LE, and I was struck by the fact that it is a smidge larger in all three dimensions than my circa 1984 15C.

Can anyone else confirm this? What about the modern 12c's - are they larger than the 1980's ones? If so, when did they "grow"? If not, I wonder why the factory would not use the same molds for both the modern 12c's and the 15c LE.

#4

Yes. Not sure about length and width but it is certainly a tad thicker. Also perhaps a very slightly different shape in the beveling along the top edge. Seems to match the 12C+ exactly.


#5

It's 5 grams heavier.

#6

I made a quick-and-dirty comparison of the 15c LE with a made-in-USA 12c, using a digital caliper. The 15c is approximately 0.025" longer and thicker, and the height is close to "no difference."

#7

It struck me as well when I was comparing my 11C and the new 15C LE. The size differences are very minimal though. The 15C fits smoothly in the 11C pouch and vice versa.

I keep wondering why the new voyagers have dual CR2032 cells and not dual AAA-size cells. I think they would fit inside the case. Wouldn't AAA-size cells last longer?


#8

You wouldn't be able to change one cell at a time without losing memory contents because AAA cells would need to be wired in series instead of in parallel.


#9

Being able to change one cell at a time really is a nice feature. Better than rushing to change the cells in series so you don't lose all memory!


#10

one could easily provide space for two AAA cells along with a small backup coin cell - assuming here that the AAA's would themselves fit in the available space.

#11

A capacitor may be designed in so to supply a minimum current, allowing to keep the memory contents for a short time (say, less than a minute) while batteries are changed. That's the way it worked in many old models such as the 25C, 41C, Voyagers, Pioneers, etc. Parallel cells schemes are rather new for HP calcs and, with due respect, not the best solution around.

#12

Quote:
Wouldn't AAA-size cells last longer?

Yes! Many, times longer because the 2032 cells are destroyed by the 20ma current load that the 15CLE has when running any function or even holding a key down. I'd estimate that you'd get less than 4 hours of program run time out of the CR2032 cells, while you'd get close to 50 hours with AAA cells.

Powering all the HP ARM-based calculators with 2032 cells is a huge engineering mistake in my view. The current load of the ARM running at more than a few MHz is too high for these size cells.


#13

If thickness is a worry, what about AAAA cells, they're about 8.3mm dia. (AAA ~10.5mm dia.), have at least twice the capacity of CR2032, however only around 1% of the internal resistance - so can cope much better with the peak current drains and probably see several times the life.

(Note, I have referenced the Energizer data sheets for info only - I have no specific like or dislike towards them).


#14

AAAA cells would be a good choice, but they are hard to find in stores. You could buy a 9V alkaline battery and rip it open to get at the 6 cells inside there (very close in size to AAAA), but how many people would know to do that?

Edited: 1 Oct 2011, 4:58 a.m.

#15

So, with the new firmware there's a chance to get the big block out of the Ford T.

#16

Quote:
Yes! Many, times longer because the 2032 cells are destroyed by the 20ma current load that the 15CLE has when running any function or even holding a key down. I'd estimate that you'd get less than 4 hours of program run time out of the CR2032 cells, while you'd get close to 50 hours with AAA cells.

Some time ago I'd considered exactly that, namely designing a
modified voyager housing with the same external envelope.
Accommodating 2x AA cells would require the vertical depth to
increase as it would compete for that space with the lcd glass.
I seem to recall an anecdote to the effect the original voyager
housing depth was extended to its current form when a third
LR44 was added to the design.

Quote:
Powering all the HP ARM-based calculators with 2032 cells is a huge engineering mistake in my view. The current load of the ARM running at more than a few MHz is too high for these size cells.

I'm not quite sure why HP didn't initially use a more conservative
clock frequency such that the current draw would be on a more
realistic point in the CR2023's discharge curve. Clocking the
sam7 at its maximum design frequency doesn't really make much
sense given the expected usage of the device. At least some
user configurable clock frequency would have been a more
flexible approach.

#17

I held my LE up against my 1982 vintage 16C and I could not see any difference so I measured them both with vernier calipers and for the LE I get 12.89cm x 7.99cm x 1.5cm at its thickest point the 16C measures 12.84cm x 7.98cm x 1.45cm so in my case the variation is insignificant.


#18

ah, yes. the biggest difference is the thickness, and your calipers are consistent with what i felt in my hand. by eye, i don't think the length and width are noticeable, but in my hand, i immediately thought it was thicker. i guess my hands are ultra sensitive or that's just how well i know my hands know my 27 year old calculator that i've used exclusively over all that time for school (HS, college, grad) and work.


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