Stand by power WP 34s & HP 35s

[abaldoni]

Hello.
I own a 35s and I use it rarely, but every time I need it, the batteries are always exhausted (so I use it even less...). Later I modified a 30b in WP 34s and I had the impression that the batteries lasted much longer.
HP declare the same duration for the two calculators (9 months @ 1h/day) so I decided to make some measurements.

Here are the results, measured at 3.00V, 28C:

WP 34s standby: 4.15uA
WP 34s on: 170uA

HP 35s standby: 6.96uA
HP 35s on: 18.3uA

The on power grow slightly with more numbers on the display, the measurements have been taken with all cleared.

If the calculators were able to use the energy of the batteries to 2V, they should last years (a single CR2032 is rated >900 hours @200uA 20C); by my experience, this is clearly not the case. It should be interesting to understand why.
Nevertheless, for low usage rates, the WP 34s wins.

Best regards,
(Mr.) Andrea Baldoni

[Waon Shinyoe]

I have the very opppsite impression on these two calculators. The batteries of my 34s can only last for several weeks. I kept my 35s for a short time, but I never met such a situation where the batteries of my 35s was exhausted.

[walter b]

I can confirm Andrea's impression: the HP-35S eats batteries pretty fast (compared to Pioneers and Voyagers) in standby mode, just sitting on the shelf. The WP 34S doesn't. I didn't take any measurements though.

d:-)

[aurelio]

(08-28-2014 11:35 AM)walter b Wrote:  I can confirm Andrea's impression: the HP-35S eats batteries pretty fast (compared to Pioneers and Voyagers) in standby mode, just sitting on the shelf. The WP 34S doesn't. I didn't take any measurements though.

d:-)

And what is, Walter, your impression if compared in standby mode (your baby) with the 42s?

[walter b]

According to my observations (matching the ones of many other folks here AFAICS) Voyagers are gold standards for low power consumption, Pioneers follow. Since you asked for my impression, I'd say the HP-30b / WP 34S / WP 31S cannot compete here. For a more solid statement that shall be measured, however - and I don't own the necessary equipment to do it.

d:-)

[Didier Lachieze]

(08-28-2014 01:14 PM)walter b Wrote:  According to my observations (matching the ones of many other folks here AFAICS) Voyagers are gold standards for low power consumption, Pioneers follow.

Excepted maybe the 17B/BII ; as it has a real time clock it's power consumption in standby mode seems to be higher than on the other Pioneers, at least it's what I've observed with a shorter battery life on my 17BII vs. my 20S, 27S, 32S, 42S.

[walter b]

I should have written that my observations cover the scientific models only. Thanks for the reminder. (I don't care much about the financial calculators unless we could use/repurpose them for something better.)

d:-)

[rprosperi]

(08-28-2014 01:27 PM)Didier Lachieze Wrote:  

(08-28-2014 01:14 PM)walter b Wrote:  According to my observations (matching the ones of many other folks here AFAICS) Voyagers are gold standards for low power consumption, Pioneers follow.

Excepted maybe the 17B/BII ; as it has a real time clock it's power consumption in standby mode seems to be higher than on the other Pioneers, at least it's what I've observed with a shorter battery life on my 17BII vs. my 20S, 27S, 32S, 42S.

The 27S has the same "clock" as the 17B, and though I'm no expert, I don't believe the clock "runs" in the nomal sense, the h/w just ticks off a counter every n mS and the "clock" interprets that counter when invoked.

That is to say, I don't believe the Pioneers with clocks should have a noticeably shorter shelf life.

I expect the real experts to weigh-in here and I look forward to the clarification if this is not correct.

[Marcus von Cube]

(08-28-2014 11:19 AM)Waon Shinyoe Wrote:  I have the very opppsite impression on these two calculators. The batteries of my 34s can only last for several weeks. I kept my 35s for a short time, but I never met such a situation where the batteries of my 35s was exhausted.

The 34S can consume up to 40mA (IIRC) when doing real work. This is hard for the 3032 cells and can lead to increased internal resistance which in turn causes an early power down even if there is still some juice in the cells. You can set SLOW mode to limit the speed, and thus the maximum current drown. This might help to increase battery life but the trade off is a longer response time in certain situations.

In order to limit the wear on the batteries I step up the processor speed whit a short delay. Many (if not most) operations never reach the point where the speed is set to maximum. Running programs is a different story though...

[abaldoni]

Hello Marcus.

(08-28-2014 06:07 PM)Marcus von Cube Wrote:  The 34S can consume up to 40mA (IIRC) when doing real work. This is hard for the 3032 cells and can lead to increased internal resistance which in turn causes an early power down even if there is still some juice in the cells.

I have made measurements with this program

LBL 00
GTO 00

the previous conditions apply: 3.00V, +28C

WP 34s FAST: 17.9mA
WP 34s SLOW: 9.28mA

HP 35s: 1.07mA

Best regards,
(Mr.) Andrea Baldoni

[Marcus von Cube]

(08-30-2014 08:49 AM)abaldoni Wrote:  WP 34s FAST: 17.9mA
WP 34s SLOW: 9.28mA

Andrea, thanks for the measurements. It's some time ago I did it myself and I was therefore recalling the wrong figures. 18mA is still way beyond the design specs for lithium coin cells I'm afraid.

So in order to keep your 34S up longer it's better to set it to SLOW mode. Or you can equip it with Harald's USB board and leave it connected to the PC or a charger. For longtime storage just make a backup with ON+STO and remove the cells.

[Harald]

I have no idea what kind of processor the HP35 uses, so the reason for the battery drain might be entirely different from the WP34s.
But there was an issue with floating input pins on the WP34s which Marcus corrected quite a while ago. If I remember correctly, the same problem was present in the original HP 30b firmware. Floating input pins on cmos devices can draw quite a bit of current. The problem was made much worse by installing one of my USB boards, simply because the wires acted as aerials feeding noise to the input pins.

[brouhaha]

(09-02-2014 02:27 PM)Harald Wrote:  I have no idea what kind of processor the HP35 uses,

The HP 35s uses a GeneralPlus (formerly SunPlus) microcontroller with a 6502-compatible core, masked ROM, and an external static RAM chip. It's a much less powerful processor than the ARM used in the 20b/30b. The firmware is written in C, and unfortunately the 6502 architecture isn't very efficient for running C code.

[pito]

There is an another design "feature" with hp30b/wp34s/wp31s - the two cr2032 batteries are wired in parallel, without any isolation diodes. It means the "stronger" battery will always discharge itself into the "weaker" one.. And there are none two batteries equal..

[walter b]

(09-09-2014 07:10 PM)pito Wrote:  There is an another design "feature" with hp30b/wp34s ...

Sorry, we - the creators of WP 34S - apologize for whatever hardware "features" you (pl.) may find though the hardware was neither designed nor made by us. Just for clarification ...

d:-/

[pito]

(09-09-2014 07:25 PM)walter b Wrote:  

(09-09-2014 07:10 PM)pito Wrote:  There is an another design "feature" with hp30b/wp34s ...

Sorry, we - the creators of WP 34S - apologize for whatever hardware "features" you (pl.) may find though the hardware was neither designed nor made by us. Just for clarification ...

d

Just referring the "currently available models based on the specific hw" which include the built in hw "feature", with none intention to claim the creators of wp34s have introduced any hw design flaw..

[walter b]

(09-09-2014 07:30 PM)pito Wrote:  Just referring the "currently available models based on the specific hw" which include the built in hw "feature", with none intention to claim the creators of wp34s have introduced any hw design flaw..

Then please include the WP 31S in your prayers.

[abaldoni]

(09-09-2014 07:10 PM)pito Wrote:  There is an another design "feature" with hp30b/wp34s/wp31s - the two cr2032 batteries are wired in parallel, without any isolation diodes. It means the "stronger" battery will always discharge itself into the "weaker" one.. And there are none two batteries equal..

Yes, however a diode drop would probably worsen the situation.
I didn't analyze the circuit, but from the behaviour while measuring currents, it seems to me that HP 35s actively switch from one battery to another every couple of seconds while on and idle (but stood on the same while running the loop program). I don't know what's happening in off state, probably it has normal diodes to power the processor enough for waking up and bypass them when on.

Best regards,
(Mr.) Andrea Baldoni

[d b]

(09-12-2014 06:29 PM)abaldoni Wrote:  

(09-09-2014 07:10 PM)pito Wrote:  There is an another design "feature" with hp30b/wp34s/wp31s - the two cr2032 batteries are wired in parallel, without any isolation diodes. It means the "stronger" battery will always discharge itself into the "weaker" one.. And there are none two batteries equal..

Yes, however a diode drop would probably worsen the situation.
I didn't analyze the circuit, but from the behaviour while measuring currents, it seems to me that HP 35s actively switch from one battery to another every couple of seconds while on and idle (but stood on the same while running the loop program). I don't know what's happening in off state, probably it has normal diodes to power the processor enough for waking up and bypass them when on.

Best regards,
(Mr.) Andrea Baldoni

My guess is that if the 34s team had had anything to do with the design of the 30b series then it would have been as perfect as the rest of the 34s is. And: if HP had only known what was going to be made from their "bean counter" calculator then they would have done some things differently.

Sam Kim showed me the ARM version of the 12C when he had Tim's job, back in I think '09. He said that that and the mythical and secret 30b series were things he hoped would be adopted by other manufacturers for other uses. He showed me how they could snap into a larger unit and become the user interface for makers who would rather let that be made by the experts. He knew that I was a surveyor and asked what I would think of a total station or data collector with an HP quality keyboard and screen. I said "dude............sign me up".

That never happened but the 34s did. Lucky in a different way.