Power Dock "Off", not Off?



  • I prodded about with a test meter earlier and it seems some current is flowing even with the on/off switch set to off?

    Disclaimer: I'm an electronics noob. I may be doing it wrong so here is my method:

    alt text

    alt text
    Obviously I would then touch the other terminal from the test meter onto the exposed power dock pin.. but I only have two hands and can't photo and perform that function at the same time :)

    And while "off" the display showed:
    alt text

    Any comments? Is the power dock "leaking" battery into something?



  • Your testing circuit looks good to me, so it does seem that an Omega feature IS NOT TURNED OFF by the ON/OFF switch of the power dock, and it consumes about 7 mA. It's not a lot (compared to a 1.5V motor that can consume 400-450 mA), but it will drain the battery over a long period of time.

    Out of curiosity, you could do the same test with only one of either your Omega module OR your expansion module into the power dock. You could even do the same test without any module. That way, you will be able to determine which component is consuming this 7 mA current, or perhaps it's a combination of them that totals 7 mA.



  • @fossette In https://wiki.onion.io/Tutorials/Expansions/Using-the-Power-Dock it says
    :

    • The Power Switch
      The power switch controls power to the Omega, regardless of whether it is powered from the battery or Micro-USB cable. The power switch has no effect on the battery charging, so the battery will charge regardless of the switch position.

    This implies that the battery (when plugged in) is always connected to the charging circuitry. Since the schematics of the Power Dock have not been published yet (To Omega Guys: it would be helpful if they were) we can't be sure what is happening, but it would not surprise me if this is the source of the drain from the batter even when the Omega is turned off and no power is supplied from the USB cable



  • @fossette Further follow up to the previous message:
    The battery supplied with the Power Dock has a capacity of 5.55Wh - this is equivalent to 1,500 mAh (at 3.7v). So with the drain of 7mA when battery is plugged in but Omega turned off and USB power not connected, one will expect a battery life of close to 9 days.

    I am using a 2,000 mAh battery in place of the standard one so can expect about a life of close to 12 days in the above scenario



  • I would guess the on/off circuitry is similar to that on the other docks (for example, see mini-dock here) - which is that the physical switch controls a MOSFET which actually switches the power.

    But such a circuit should consume a few microamps maximum in the off state. 7mA is IMHO way too much. The charging circuitry (which we don't know – @Kit-Bishop: I agree it would be helpful to have the schematics!) should definitely not consume 7mA either.

    One possibility would be capacitors charging in the moment the battery is connected, but then the current should go down to near zero after a few seconds. @None-None, did you manage to keep the meter's terminal for server seconds steady to the battery connector?



  • @Kit-Bishop @fossette I've re-tested without anything connected. So just the power dock and no Onion, 1-wire sensor or OLED display.. same power "leak".

    Seems to hang at around 4.2mA but then if you disconnect and reconnect within about 500ms or 1 second it can jump and stay as high as 9.2mA!

    https://vimeo.com/184930331

    Sorry the video doesn't show me connecting and disconnecting - I only have two hands which were required to hold the meter probes while the camera was balanced on top of a cup looking at the display!

    Disappointing as it means my project (as someone calculated) seems to run the battery down even while off in about a week. Not too much trouble to splice in a physical switch between the battery and the dock but I feel like this shouldn't be a problem in the first place.



  • Thanks for your tests! Now we know what is going on. I don't know the reasons behind this 'feature'. It may be disappointing to learn that an ON/OFF switch doesn't really switch a system to OFF, an understandable expectation. However, 'intelligent' hardware we see on the market today, like TVs, has an ON/OFF switch, but it's more an ON/SLEEP function (perhaps with reduced power consumption during the sleep state). Some circuits need to be powered all the time. For example, how would the remote control power ON the TV if it was actually switched to OFF?



  • Hmmm... could you maybe give a nice high res picture of the power dock itself (so that the chips are readable)? Maybe that could help to "reverse-engineer" the power circuitry because onion doesnt has any schematics for it available



  • @Matthias-Nowak Here is my rather dusty and cat hair covered dock photo! Sorry it is so grotty.
    I've tried to annotate all the ones I could read.
    alt text



  • @None-None nice. i will take a look at the whole circuitry when im back from holidays in 4-5 days!
    But my first guess would be that (although i havent looked into its circuitry) that the protection circuit also discharges the battery? because normally you want them to be at ~70% of their load when storing them


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