WP 34S Power Requirements



#4

After having worked on the power saving code recently, I just made new measurements of the power drain of my lab 20b. Here are the results (all values in mA):

State     FAST    SLOW  
-----------------------------------------------------
off 0 No display
sleep 0.15 LCD running
idle 0.82 LBL B; PSE 99; GTO B
debug 1.66 ON+D
serial 6.60 3.15 without the cable connected
run 20.5 8.99 LBL A; GTO A

SLOW can be set with the SLOW command or ON+1 (the latter behaving exactly like a low power situation). The SLOW command survives a power cycle, ON+1 is transient.

I'll probably reduce speed to the slow mode (20 MHz) for serial I/O if it proves to be reliable enough, just to save some power during the "Wait..." phase. The cable furnished by HP draws about 1.5 mA alone, even while the calculator is turned off!

I'd love to see measurements by people with better lab equipment then mine. How is the original firmware by HP (20b and 30b) performing in a similar setup? I'm looking forward to your feedback.


#5

The converse of SLOW is (of course) FAST.

SLOW slows the device down and saves power, FAST speeds it up again. By default the 34S runs in FAST mode.

As Marcus, mentioned the speed setting is preserved over a power cycle and the state is saved in the mode flags (STOM/RCLM) and in the flash backup. This means that the speed setting is pretty sticky.


- Pauli

#6

Having viewed DaveJ's Video Blog #4 I'm rethinking my approach at the high operating speed versus power loss in the batteries.

I might reduce the normal operation speed in manual mode (no program running) to a much lower value and bump it up to maximum speed only for long running calculations. This will slow down operations like factorial considerably but would save battery power while the calculator is used for manual calculations. What do you think and what slow down factor wold be acceptable?

Dave, your opinions, please! You're probably the one to verify my measurements.


#7

I don't have a WP 34S, so cannot verify anything unfortunately, but I can't think of a good reason why slower speed wouldn't be a wise default choice for non-programming mode.

To me, battery life is top of the priority list for a hand held calculator. As the device is useless if it doesn't work. And the lower the power consumption the longer "bonus time" you have between the battery indicator coming on and having it just die on you.

Is the battery indicator used in the WP 34S?, and if so, at what voltage? (and is it adjustable?)

Perhaps have it as a user option if possible? Defaulting to the lowest power, and have an optional "turbo" mode.

Dave.


#8

If you've got a 20b or 30b I can "improve" it for you :-)

We have two speed settings. Marcus should be able to elucidate as to the exact settings and the low battery thresholds. I do know the clock is slowed if the battery voltage drops too low.


- Pauli


#9

I don't have either unfortunately.

And alas, I don't think I have much need for another scientific calc, unless it can go on my wrist!

And DAMN you people! :-P, I haven't been on the forum for ages and almost forgot all about my Mk2 uWatch design. And I come back to all this new calc excitement and I may just have caught the bug again...

Dave.


#10

Quote:
And DAMN you people! :-P, I haven't been on the forum for ages and almost forgot all about my Mk2 uWatch design. And I come back to all this new calc excitement and I may just have caught the bug again...

Which is good, since I have wanted a uWatch for a long time but you won't make a new batch, and so I can't wait for a Mk2 to come out (though I'd also be happy to find an old, used mk1! :)

Cristian

#11

Dave, I thought you were collecting every electronic toy you can get at. ;-)

The battery indicator comes on at 2.4V and slows down the device to a maximum of 20 MHz. The same effect can be achieved by the user with a command. Somewhere near 1.9V the device will be turned off by the firmware.

Most of the time, the processor sleeps with the core completely turned off and only the LCD drivers and PIOC running to wake it up. Then there is a more active idle mode with interrupts running. This mode can be seen with the PSE command. The mode is used whenever the firmware does more then just waiting for the next keystroke but not executing a command.

Whenever the calculator is doing something beyond this, it's switched to either 20 or 37 MHz.

#12

Quote:
And alas, I don't think I have much need for another scientific calc, unless it can go on my wrist!

Not even one with a parallel operation on the keyboard :-)


Quote:
And DAMN you people! :-P, I haven't been on the forum for ages and almost forgot all about my Mk2 uWatch design. And I come back to all this new calc excitement and I may just have caught the bug again...

Put me on the pre-order list :-)


- Pauli


#13

Quote:
Not even one with a parallel operation on the keyboard :-)

Damn, so there is!

Quote:
Put me on the pre-order list :-)

Helps if I design it first :->

I think I'll scrap my existing designs with the capacitive touch keyboard like on the uCalc. I'm now eyeing off a nice large touch screen. Albeit still only 128x64, but it's big so you can actually use it.

And now I have a bright idea of utilising an existing commercial modular watch band attachment, allowing the unit to simply snap in and out of the watch band, so it could be used as either a watch or a tiny pocket calc.

Alas, consulting work just popped up this last hour which will be whipping my butt for the next week at least :-(

If anyone knows of any small low power touch screen LCD's, please link them my way.

Dave.


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