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P123-A7 power supply issue (Fixed! [I think]) — Parallax Forums

P123-A7 power supply issue (Fixed! [I think])

RaymanRayman Posts: 11,810
edited 2015-11-11 16:23 in Propeller 2
I've already mentioned this in a couple threads, but just want to show a cool picture...

The issue is that the power supply goes bananas when first turned on (blue power light flickering).
Then, after a couple minutes it's fine.
So, I don't really have a big issue and I'm not asking Parallax to do anything about it.

Anyway, I'm trying to diagnose it myself with FLIR Lepton thermal imager connected to P1.
This hasn't helped yet, but it's pretty neat.
Here's a snapshot of the P123 board (you can see Cyclone and something in the power supply are the hot things):
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Comments

  • RaymanRayman Posts: 11,810
    Someone said they found a bad solder bridge under a SMT capacitor this way.

    I'm looking around my P123, but don't see anything.
    Was worth a shot anyway...
  • Rayman wrote: »
    I've already mentioned this in a couple threads, but just want to show a cool picture...

    The issue is that the power supply goes bananas when first turned on (blue power light flickering).
    Then, after a couple minutes it's fine.
    So, I don't really have a big issue and I'm not asking Parallax to do anything about it.

    Anyway, I'm trying to diagnose it myself with FLIR Lepton thermal imager connected to P1.
    This hasn't helped yet, but it's pretty neat.
    Here's a snapshot of the P123 board (you can see Cyclone and something in the power supply are the hot things):

    One corner of the Cyclone looks warm, did you have just one or two cogs running when you took the image?
  • 78rpm wrote: »
    Rayman wrote: »
    I've already mentioned this in a couple threads, but just want to show a cool picture...

    The issue is that the power supply goes bananas when first turned on (blue power light flickering).
    Then, after a couple minutes it's fine.
    So, I don't really have a big issue and I'm not asking Parallax to do anything about it.

    Anyway, I'm trying to diagnose it myself with FLIR Lepton thermal imager connected to P1.
    This hasn't helped yet, but it's pretty neat.
    Here's a snapshot of the P123 board (you can see Cyclone and something in the power supply are the hot things):

    One corner of the Cyclone looks warm, did you have just one or two cogs running when you took the image?

    Or is it the egg-beater hub?
  • Ray,

    Aside from it not helping with your power issues, thermal imaging from a P1 is pretty darn cool!! It looks like you have enough pixel resolution across something the size of a 1-2-3 board to do some useful things. Certainly another fun Propeller avenue to explore!
  • RaymanRayman Posts: 11,810
    Here's a close up of the cyclone chip:

    It does have P2 firmware, but isn't running any Prop code...
    506 x 387 - 11K
  • Rayman wrote: »
    Here's a close up of the cyclone chip:

    It does have P2 firmware, but isn't running any Prop code...

    I wonder if it is where the hub egg-beater is located in the fpga image? Might be interesting to know at some point?
  • cgraceycgracey Posts: 13,371
    Daniel and I were talking about this last night. He said the Prop123 board's switching power supplies use resistors to set overcurrent protection. He felt the resistor value he chose for the supplies was causing overcurrent sensing to occur way too early, which he thinks is causing this flakiness. This resistor value has been changed for the A9 board to make it more reliable.

    I will find out where those resistors are and what value is more ideal, so that anyone can change them if they want to.
  • cgracey wrote: »
    Daniel and I were talking about this last night. He said the Prop123 board's switching power supplies use resistors to set overcurrent protection. He felt the resistor value he chose for the supplies was causing overcurrent sensing to occur way too early, which he thinks is causing this flakiness. This resistor value has been changed for the A9 board to make it more reliable.

    I will find out where those resistors are and what value is more ideal, so that anyone can change them if they want to.
    Aren't the A9 boards supposed to be available in November? I'm planning to trade my A7 for an A9 anyway so I guess it isn't worth bothering to replace the resistors. You can replace them when I send my A7 board back for the exchange! :-)

  • cgraceycgracey Posts: 13,371
    Yes, the first A9 board came off the PnP yesterday, but it looks like some parts were put in the wrong places, because the switching supplies aren't coming up. I'm working on that today.
  • jmgjmg Posts: 14,592
    Rayman wrote: »
    The issue is that the power supply goes bananas when first turned on (blue power light flickering).
    Then, after a couple minutes it's fine.

    What drives the LED ? just a Series R from Vcc ?
    Flickering suggests wide Vcc fluctuation in that case.
    What does a scope show ?

    I'd be a tad worried about AC modulation peaks damaging the FPGA.

  • cgraceycgracey Posts: 13,371
    Rayman wrote: »
    Here's a close up of the cyclone chip:

    It does have P2 firmware, but isn't running any Prop code...

    That camera is really neat! Does it use any lens, or would one interfere with the heat?
  • RaymanRayman Posts: 11,810
    edited 2015-10-30 23:22
    It does have a lens, there are two options for FOV.

    The additional lenses or windows do have to be a special material to transmit between 8 and 12 um.
    The options I know of are ZnSe, Silicon and Germanium.
    ZnSe is a pretty standard thing you can buy
  • RaymanRayman Posts: 11,810
    That overcurrent protection resistor idea makes sense...

    I'm seeing something else too. If I set LCD backlight to full on (I think ~400 mA from 3.3V supply, it reboots after a few seconds.

    It's fine if I turn down the backlight.

    Maybe this is a related thing, or maybe it's a real overcurrent....
  • RaymanRayman Posts: 11,810
    edited 2015-10-31 23:54
    If Parallax does say where that resistor is, I think I would try changing it out...

    Or maybe not, it's good enough like it is, I suppose...
  • rjo__rjo__ Posts: 2,115
    im using a minikeypadded ipad cant find the apostrophe:)

    i dont know about all of this. Brian hasnt reported a problem and I havent
    had so much as a hickup since connecting that hidden pad to ground. Of course we aren
    t using the plls yet. Things might get more interesting then.

    So im thinking... maybe it is just what happens when that pad floats.

  • I have a floating #1 ball but haven't seen any power supply issues.
  • 11 cogs running and all the leds, no power issues observed here. :)
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2015-11-01 06:47
    FPGAs do seem to be a bit piggish about power when you use them near full capacity. Migrating from 'hello world' and tutorial examples to the P2 image may indeed display a significant increase in power demand and related heat.

    There was a lot of similar discussion and concern with the BeMicroCV and the BeScope as an extra and separate power for the daughter board was actually required.

    So the situation may just be typical to all FPGAs. As long as the power supply can deliver enough, the device should perform. Maybe a glue on heatsink would offer some comfort to the worried. I think I even have one or two that I purchased for the SX-48.

    In other words, FPGAs will likely generate a lot of comments about 'why is it so hot?' when you begin to use most of what it can do.

    I suspect that best thing to do is to run a 24/7 burn in test with all cogs churning. It really is up to Parallax to try that one.
  • cgraceycgracey Posts: 13,371
    Rayman wrote: »
    If Parallax does say where that resistor is, I think I would try changing it out...

    Or maybe not, it's good enough like it is, I suppose...

    Do you know how stout your input power supply is? If it's not that capable of delivering current, it's output voltage could be getting sagged down, causing the problem.
  • RaymanRayman Posts: 11,810
    edited 2015-11-03 00:03
    I'm using the DE2-115 supply...

    Guess I could try a bigger one..
  • cgraceycgracey Posts: 13,371
    Rayman wrote: »
    I'm using the DE2-115 supply...

    When running the backlight, which seems to be a big current hog, check the voltage on the center pin of the power jack from its back side. See if it's sagging. You might just need a higher current wall pack.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2015-11-03 10:49
    Since I mentioned glue-on heat sinks, I followed up with a bit of research.

    Not sure about the P123-A9 power req, but the somewhat similar BeMicroCVA9 has provided a 5V, 3 amp power supply, and more might be required in some configurations. That may NOT be a good comparison as the BeMicroCVA9 has added DDR3 memory and different capacities.

    There seems to be a raging debate about what glue is proper for gluing these heat sink devices in place, with a commercial silver powder based glue proving superior thermal conductivity. Arctic Silver 5 claims to be superior to all (I have no way of verifying, but their presentation is compelling.) http://www.arcticsilver.com/as5.htm

    Also, the epoxy IC case is a thermal insulator. So actually gluing the heat sink to the underside of the circuit board may provide better cooling that gluing the heat sink to the top of the device.
  • There are special foils for 'even' heat transfer on XY direction. It is used on smartphones to avoid a hot spot. I saw some videos on youtube using those foils with IR cameras but I cannot find them know.
  • I'm not seeing any thermal issues with the A7 board.
    My board has been running for 48 hours with 11 cogs running and the cyclome V chip isn't hot at all.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2015-11-03 15:48
    Good, that seems to be a resonable burn-in test.

    Rayman provided FLIR photos, but no indication of how to gage if the heat is excessive or incidental. It would have been nice to have a surface temperature reading along with the FLIR images.

    I wonder if those pyrolitic sheets are intended to divert heat away from circuit board hot spots, lithium cell hot spots, or both. We may never know.
  • RaymanRayman Posts: 11,810
    I fixed it !

    Soldered a 100k 0605 resistor on top of another resistor and now it's all better :)
    Can even run LCD backlight on full.

    Here's a photo of the new resistor (with red circle around it):
    922 x 627 - 1M
  • Cool! I'm curious to see how my P123 board works with your add-on board. I may have some soldering in my future!
  • jmgjmg Posts: 14,592
    Rayman wrote: »
    Soldered a 100k 0605 resistor on top of another resistor and now it's all better :)

    Which is changing what, exactly ?
  • RaymanRayman Posts: 11,810
    Good question... Maybe this is the current limit resistor..
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