HP Forum Archive 20

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HP 15C and 15C LE not the same dimensions? Message #1 Posted by Derek on 30 Sept 2011, 3:55 p.m. 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.

Re: HP 15C and 15C LE not the same dimensions? Message #2 Posted by Martin Pinckney on 30 Sept 2011, 4:38 p.m., in response to message #1 by Derek 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.

Re: HP 15C and 15C LE not the same dimensions? Message #3 Posted by M. Joury on 30 Sept 2011, 4:48 p.m., in response to message #2 by Martin Pinckney 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.

Re: HP 15C and 15C LE not the same dimensions? Message #4 Posted by Michael de Estrada on 30 Sept 2011, 4:58 p.m., in response to message #3 by M. Joury It's 5 grams heavier.

Re: HP 15C and 15C LE not the same dimensions? Message #5 Posted by Jeroen Van Nieuwenhove on 30 Sept 2011, 5:04 p.m., in response to message #2 by Martin Pinckney 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?

Re: HP 15C and 15C LE not the same dimensions? Message #6 Posted by Marcus von Cube, Germany on 30 Sept 2011, 5:12 p.m., in response to message #5 by Jeroen Van Nieuwenhove 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.

Re: HP 15C and 15C LE not the same dimensions? Message #7 Posted by Dwight Sturrock on 30 Sept 2011, 11:40 p.m., in response to message #6 by Marcus von Cube, Germany 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!

Re: HP 15C and 15C LE not the same dimensions? Message #8 Posted by robert rozee on 1 Oct 2011, 1:03 a.m., in response to message #7 by Dwight Sturrock 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.

Re: HP 15C and 15C LE not the same dimensions? Message #9 Posted by Andrés C. Rodríguez (Argentina) on 2 Oct 2011, 8:18 p.m., in response to message #6 by Marcus von Cube, Germany 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.

Re: HP 15C and 15C LE not the same dimensions? Message #10 Posted by Katie Wasserman on 1 Oct 2011, 3:05 a.m., in response to message #5 by Jeroen Van Nieuwenhove 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.

Re: HP 15C and 15C LE not the same dimensions? Message #11 Posted by Bart (UK) on 1 Oct 2011, 3:32 a.m., in response to message #10 by Katie Wasserman 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).

Re: HP 15C and 15C LE not the same dimensions? Message #12 Posted by Katie Wasserman on 1 Oct 2011, 4:55 a.m., in response to message #11 by Bart (UK) 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.

Re: HP 15C and 15C LE not the same dimensions? Message #13 Posted by Thomas Radtke on 1 Oct 2011, 4:46 a.m., in response to message #10 by Katie Wasserman So, with the new firmware there's a chance to get the big block out of the Ford T.

Re: HP 15C and 15C LE not the same dimensions? Message #14 Posted by uhmgawa on 2 Oct 2011, 9:03 p.m., in response to message #10 by Katie Wasserman 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.

Re: HP 15C and 15C LE not the same dimensions? Message #15 Posted by John S. Miller on 30 Sept 2011, 4:52 p.m., in response to message #2 by Martin Pinckney 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."

Re: HP 15C and 15C LE not the same dimensions? Message #16 Posted by Paul Berger (Canada) on 30 Sept 2011, 5:13 p.m., in response to message #1 by Derek 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.

Re: HP 15C and 15C LE not the same dimensions? Message #17 Posted by Derek on 30 Sept 2011, 5:33 p.m., in response to message #16 by Paul Berger (Canada) 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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