"Conserve Power" with TX's WiFi

Discussion in 'Palm' started by Gregte, Mar 2, 2007.

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  1. Gregte

    Gregte TX lifer

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    I was curious about the checkbox in WiFi prefs called "Conserve Power" so I did some experimenting and found out something quite interesting about the TX.

    First, I used an external battery pack (4 NiMH cells) to power my TX with an ammeter connected. With screen at a very low brightness and just in the Launcher the current draw was 150 milliamps. With WiFi turned ON but NOT connected to a wireless access point the current drawn was 285 mA. But when I tapped Connect and connected to my Apple wireless base station the current actually dropped a whole 110 mA to 175 mA. I naturally double checked everything and repeated this several times and confirmed that these numbers were correct.

    The above was all with the "Conserve Power" box checked in Prefs. I next tried the same measurements with the box UNchecked and found that the difference is that the current draw remains at the high 285 mA whether WiFi is ON and unconnected or ON and connected.

    Having WiFi ON and "connected" only uses 25 mA more current than having WiFi OFF. Having it ON and UNconnected is the bad power drain.

    Having WiFi ON, Connected and NOT downloading with Blazer draws 290 mA.
    Having WiFi ON, Connected and downloading with Blazer draws 345 mA.

    During actual downloading websites the current draw is the same regardless if Conserve Power is checked or not. The value of Conserve Power is when the WiFi IS connected but is idle, i.e. not TXing and RXing data. And if your WiFi is going to be ON it is far better that it is connected to an access point and with Conserve Power checked than it is to just be ON and not connected.
     
  2. RickAgresta

    RickAgresta Peanut, leader of the Peanutty Forces

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    v. interesting stuff, Gregte-- thanks for posting it. it'd be nice if I understood why more amperage is drawn when idle than when connected (conserve checked); it seems counterintuitive. :confused:
     
  3. Donx

    Donx Mobile Deity

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    I'd be interested to see a similar analysis of having bluetooth on/off. I just went and turned off WiFi.
     
  4. FerdFerd

    FerdFerd Recovering Palm Fiddler

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    Funny, in practice I can't notice any difference in battery drain between WiFi on and off, as long as I'm not connected. My router drops my TX if I use the conserve power option, which is a nuisance. Your post reminds me of that!
     
  5. mmaestro

    mmaestro Mobile Evangelist

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    I had always been under the impression that wifi didn't drain power while it was disconnected, but my real world experience is different. I use my TX during the day as an mp3 player, mainly, and when I don't bother to turn wifi off at the start of the day, the battery will usually be drained by 3 in the afternoon. With it off, I'll make it through the whole work day (although only just, assuming a bit of E-mail and the like during my lunch break).
    Realworld experience would also indicate that leaving Bluetooth on throughout the day does drain the battery, although not by much, and connecting using Bluetooth uses a lot more.
    To really notice either, I find you need the TX on for a long period of time, a matter of hours (which you'll only manage at all if your screen is off), but it does seem to make a difference.

    Mmaestro
     
  6. mansfield

    mansfield Palm Enthusiast

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    I'd be interested in the results from the "current" test at varying distances from the wireless router. My experience has been the farther away, the shorter the battery life.

    I guess I could try it myself, huh?
     
  7. jfindon

    jfindon Mobile Deity

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    Maybe the TX somehow constantly scans for connections when it isn't connected or something? I don't know either.
     
  8. Gregte

    Gregte TX lifer

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    I have done this also with bluetooth. Bluetooth draws almost no measurable current when merely turned ON. I have done this measurement in the past with the ammeter connected in the TX's internal battery supply as well as doing it with the meter in the circuit of an external battery pack and the results are the same.

    What bluetooth does when turned ON but not transmitting and receiveing is it sends out a very short low power pulse periodically (don't remember the frequency) but they are so short that they add up to virtually no measurable drain on the battery. I leave bluetooth turned ON all the time just for convenience.
     
  9. Gregte

    Gregte TX lifer

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    This seems very odd. I wonder if there is some difference between your TX and mine such as the software we have installed? The power used by WiFi on mine is very significant. I definitely notice that the battery drains faster if I leave WiFi ON.

    I occasionally forget to turn WiFi OFF when I am not using it. I think it is sad that Palm made some of the status bar icons so difficult to tell if they are On or OFF or active, or if you have pressed a key on the virtual keyboard or not. I guess eye candy was more important than usability.
     
  10. yorker

    yorker Mobile Deity

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    Welcome to Brighthand, mmaestro!:D
     
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