Prop123-A9 power issue

RaymanRayman Posts: 11,687
edited 2016-02-13 (6:28 PM) in Propeller 2
So, I seem to have some bad luck or something...

My old A7 P123 board had a major power issue that I eventually fixed myself with hardware hack:
http://forums.parallax.com/discussion/162639/

Was very glad to trade in for A9 board.
This one has worked perfectly ... Until today.

Today, it was acting exactly like my old A7 board did. The power LED (and lots of other LEDS) was blinking on and off every couple seconds.

Just like the A7, it eventually fixed itself. Just wait a few minutes, cycle power, and it's all better.

I have to confess that I haven't used my P123 board for a few weeks now.
My guess is that there is some capacitor that gets discharged very slowly and things won't work right until it gets charged back up.

Anybody else seen this? Is it just me?
Maybe I'm the only one who ignored their P123 board for a long time...

Comments

  • I think I figured it out... My P123 board doesn't like the cold!

    Record low temps here have made it colder than usual at my desk here.
    Did a little experiment:

    Put P123 in refrigerator for 5 minutes then test --> power led is very dim and flickering like crazy
    Put P123 in front of heater for 1 minute then test --> works perfectly.
  • One P123-A9 board just gone into the fridge here ...
  • jmgjmg Posts: 14,572
    Rayman wrote: »
    Put P123 in refrigerator for 5 minutes then test -->
    Is that the Freezer compartment, or just the chiller ?
    Any Temperature numbers ?
    Most variable parts with Temp, are capacitors - did you check the rails for oscillation ?
  • RaymanRayman Posts: 11,687
    edited 2016-02-14 (8:04 PM)
    Not the freezer.
    The power was cycling on and off very quickly so I'm sure the rails had oscillations...
    I'd also guess it is a capacitor that is changing value too much...
    Curious to see what evanh sees. Pretty brave to do this on a working board...
  • jmgjmg Posts: 14,572
    Rayman wrote: »
    Not the freezer.
    The power was cycling on and off very quickly so I'm sure the rails had oscillations...
    I'd also guess it is a capacitor that is changing value too much...
    Curious to see what evanh sees. Pretty brave to do this on a working board...
    Yes, caution would be advised.
    What does a scope show on the rails ?
    Are they going outside limits, and/or just restarting / hiccup ?

  • Two hours in the fridge and no issue. Tried both 12.5V and 8.2V input supply.
  • Another 45 minutes in freezer and still good. Tried 7.5V to 13.0V. There was the odd full bright colour LED in initial power on but every time it went away after firmware booted.
  • potatoheadpotatohead Posts: 10,141
    edited 2016-02-15 (6:39 AM)
    I had trouble with cold with my DE2 board. Under freezing would result in very erratic behavior, FWIW.

    (In case anyone wonders, I have it near an open window. The room is warm, but the air coming in isn't, and I like the nice cool breeze mixing with the heat. That's how it happened)
  • TubularTubular Posts: 4,223
    edited 2016-02-14 (11:00 PM)
    Just a thought but not related to the input connector diameter by any chance? Ie a 2.5mm dc plug making less contact with 2.1mm pin?

    I haven't seen any issues so far, but am in a mild climate


  • This isn't a joke. When I cook spaghetti... I end up putting the hot pan in the fridge. To keep it from drying out I also keep a glass lid on it. When it is time for spaghetti again... I take it out of the fridge and put it back on the burner. Immediately there is condensation on the lid.

    I suspect that the P123 isn't water proof.
  • If Parallax decides to go industrial with the board, a temperature sensor and some protection scheme seems to be a good idea. I haven't done any drop testing... but adding in a diagnostic accelerometer might not be a bad idea. and if you go that far, why not just drop in 10dof jfthoi.
  • It seems to me that the switcher needs current-limiting to be set higher. Daniel changed the resistor value to raise it, but maybe we didn't go far enough.

    Rayman, I think the switcher resistors are in the same place as before. You might try the same fix as you made last time.
  • evanhevanh Posts: 10,230
    edited 2016-02-15 (8:22 AM)
    5.5 hours in the freezer this time, all good again. Went as low as 6.9 volts this time also. I'll assume I got a different resistor value than Rayman.

    PS: Nice film of condensation on the PCB now ... :D

  • Thanks for testing. Must be I have bad luck...
    Interesting that potatohead saw similar thing with DE2.
    I think that board has a similar power supply circuit, maybe that's why.

    My board is fine now. I just have to either keep it on or warm it up. Not a big deal.
  • potatoheadpotatohead Posts: 10,141
    edited 2016-02-15 (4:27 PM)
    Yeah, I mentioned here quite some time back. Don't get 'yer DE2 too cold. It got pretty cold again with the A9, but this is Northwest Oregon. Won't be that cold very often. No issues with it so far.
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