Power leakage puzzle - Solved embarassingly



  • The prior and current version (long frustrating story) powered the JSN-SR04-2.0 ultraonic board via a signal relay so US power is cut prior to the Arduino sleeping, but the current 3.3v version no longer has a level converter (which was powered off between reads) inserted between the Pro-Mini and the ultrasonic board to handle Trigger and Echo needed when it was running on 5v.
    What I have noticed since this version is a rather sharp degradation in battery voltage which is puzzling, since no power goes to the board during sleep. The Output Trigger pin as normal is set LOW before reading the Input Echo pin prior to cutting power and going to Sleep, and there is no other connection other than the Echo input, which implies power is being lost via the Input pin
    There is a spare contact on the Relay if necessary to sever the Echo line but a little surprised.
    Does this make sense ?
    0_1561411345588_d0dab81c-64e0-45f5-ad09-81698aabd34a-image.png



  • Have you disabled internal pull-up resisters? on the ATmega 328?
    Maybe try:
    What is the current consumption when no JSN-SR04-2.0 is attached?
    If this is low, then try to measure current that the JSN-SR04-2.0 is using?



  • @bjacobse Because of available pins I'm using pins A2/D16 as digital In and A3/D17 as digital Out, no internal pullups are disabled.

    This is one of a pair of identical Nodes, with onboard RTC initiating an hourly update (usually<1 sec). The other is fairly recently converted so too early to see if the problem is replicated.
    This one lost 0.9v in 16 days compared to 0.26v on the other, and one of the US boards has the LED butchered, but cannot recall which.
    It's a bit tricky to measure the current as would need to insert meter then reprogram the RTC again, but the Arduino is specced low microAmp sleeping, the US is specced at < 8mA running, but leakage appears to be during sleep when all power is cut to the US.
    May just try connecting the Echo for a week via the spare relay contact to see if that affects it, then Trig if that fails.
    Curious why disabling internal pullups would make any difference?



  • Long story short, problem found to be the US running for 19 days continuously but couldn't tell as had detached the board's LED in an earlier itteration where power indication was from the booster.
    Fault was a detached Dupont connection for the latching relay reset, only discovered when probing found the relay was not off, and went to reset it by removing the Arduino pin connection to power it direct, ending up with the entire wire in my hand.
    Reconnected relay board and it felt tight, reset the relay then reconnected to the Arduino pin before the next due 12 hourly battery check, 1.76v recovered to 1.87 in 30 minutes and rising.
    Can only presume I disturbed the connection somehow, but kicking myself about removing the LED, and not thinking to listen for clicks from the relay as a check on Set/Reset.😳
    Ho-hum, next a fresh pair of AA to start over again, well over a year is back in the frame again.


 

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