HP Forum Archive 20

[ Return to Index | Top of Index ]

dealing with 20b/30b/wp34s power drain Message #1 Posted by hugh steers on 18 Apr 2011, 9:37 a.m. fed up with burning button cells? cells die during flashing? here is the answer! is fine on desk too. :-)

Re: dealing with 20b/30b/wp34s power drain Message #2 Posted by Walter B on 18 Apr 2011, 10:17 a.m., in response to message #1 by hugh steers Hi Hugh, you created the backpacker's calculator d:-)

Re: dealing with 20b/30b/wp34s power drain Message #3 Posted by hugh steers on 18 Apr 2011, 2:25 p.m., in response to message #2 by Walter B more seriously, i do think HP should consider a model with a slightly thicker part to accommodate maybe AAA batteries. This would give a much extended battery life, could afford to run the processor faster on average, plus it could provide the current to drive a micro SD card slot. my hack shown in the pictures is the result of some goose chase regarding weak button batteries. basically, i had a situation where the unit did flash, but drained the battery whilst doing so to the point that it wouldnt operate the unit. i thought i'd bricked it until i tried driving from a psu. incidentally, im thinking the WP34s rom requires more current to run, since a weak battery wouldnt activate it, but the same battery worked in another unit. something to watch out for. -- hugh.

Re: dealing with 20b/30b/wp34s power drain Message #4 Posted by Marcus von Cube, Germany on 19 Apr 2011, 12:16 p.m., in response to message #3 by hugh steers Quote: incidentally, im thinking the WP34s rom requires more current to run I'm working on it...

Re: dealing with 20b/30b/wp34s power drain - new findings Message #5 Posted by Marcus von Cube, Germany on 19 Apr 2011, 1:49 p.m., in response to message #4 by Marcus von Cube, Germany To be more precise: I'm now able to power the processor down when there is no program running and no key down. This lowers the current draw to 0.15 mA. I have the feeling that this is just the PIO being active for wake up. During a programmed pause, the CPU stays on and the current draw is between 0.25 and 0.3 mA. With full power at 32 MHz, the demands are significantly higher. I measured 15 mA while a program was running. In my very first attempts, in CPU off mode the draw was higher than with the PIO off but the CPU on. That was until I figured out that I had the pull-up resistors active on the outputs which were tied low. I must have measured the current flowing through these resistors (summing up to 0.4 mA). Tim, what does the 20b firmware demand on the batteries in idle mode? Can I get below my 0.15 mA? BTW, the new image is on SF in the repository.

Re: dealing with 20b/30b/wp34s power drain - new findings Message #6 Posted by Marcus von Cube, Germany on 20 Apr 2011, 4:54 a.m., in response to message #5 by Marcus von Cube, Germany Paul has reported problems with the stability of the last build (699). As a measure, I've relaxed the power saving strategies slightly. Turning of the flash rom while idling doesn't seem to save enough power to be worth the hazzle. So it's gone for now. Going to processor off mode is now postponed to half a second after the last keystroke. You can see it by watching the tiny equals sign in the display. The new release is in the repository. If it is reported to be stable I'll put it in the standard download.

Re: dealing with 20b/30b/wp34s power drain - new findings Message #7 Posted by Marcus von Cube, Germany on 20 Apr 2011, 10:39 a.m., in response to message #6 by Marcus von Cube, Germany Once again! I've posted another update of the flash image to the SVN repository. The auto power down feature which is supposed to turn the calculator off after about three minutes of inactivity seems still to be a bit flaky. Please try out the new build!

Re: dealing with 20b/30b/wp34s power drain Message #8 Posted by Paul Dale on 18 Apr 2011, 5:48 p.m., in response to message #1 by hugh steers All that effort to save replacing some twenty five cent button cells :-) - Pauli

Re: dealing with 20b/30b/wp34s power drain Message #9 Posted by robert rozee on 18 Apr 2011, 7:07 p.m., in response to message #8 by Paul Dale Quote: All that effort to save replacing some twenty five cent button cells a more accurate response would have been : All that effort to save THE INCONVENIENCE OF replacing some twenty five cent button cells it's not so much the cost of the batteries i suspect, but the hassle of having to change them so often. the cost of a pair of 2032 cells is miniscule compared to the cost of the petrol consumed driving down to the battery shop, and the time taken for the trip.

Re: dealing with 20b/30b/wp34s power drain Message #10 Posted by Paul Dale on 18 Apr 2011, 7:11 p.m., in response to message #9 by robert rozee Buy them in bulk lots from eBay or the like. Then they arrive at your door and the price is still twenty five cents including shipping. At least this is what I do for button cells. - Pauli

Re: dealing with 20b/30b/wp34s power drain Message #11 Posted by hugh steers on 19 Apr 2011, 9:16 a.m., in response to message #10 by Paul Dale it only takes for those button cells to be not quite tip-top, and there's a problem, either flashing or operational brown out (try Q^-1). you'll all be crying into your beers when you're hacking at 3am and run out of 'em :-) but more seriously, now ive made my paper overlay and have the 34s here on my desk, the angle incline is rather nice. doesn't rock about either! :-) PS. how do i enter more than 12 digits in DEC 10 mode?

Re: dealing with 20b/30b/wp34s power drain Message #12 Posted by Walter B on 19 Apr 2011, 9:21 a.m., in response to message #11 by hugh steers Hugh, Quote: how do i enter more than 12 digits in DEC 10 mode? ?? FIX, SCI, ENG? :-) Walter

Re: dealing with 20b/30b/wp34s power drain Message #13 Posted by Paul Dale on 19 Apr 2011, 4:56 p.m., in response to message #11 by hugh steers Quote: PS. how do i enter more than 12 digits in DEC 10 mode? You can't directly. - Pauli

Re: dealing with 20b/30b/wp34s power drain Message #14 Posted by gene wright on 19 Apr 2011, 5:07 p.m., in response to message #11 by hugh steers Just buy a pack of 100 of the coin cells off ebay. That will last quite a while. Cost? About $10-15 or so?

[ Return to Index | Top of Index ]

Go back to the main exhibit hall