Kiwi2 no longer powering [Kiwi replaced]

F5MMXF5MMX
edited July 10 in Problems Now Fixed

Hi there!!

I tried to log onto my Kiwi2 and found that it was not powered any more, checked the power supply -> 5V OK, plugged it again and I saw a quick burst light on the blue LED located between the USB and Ethernet ports. The board no longer booted.

I separated the Beaglebone from the Kiwi board, hooked it to my computer, it went alive and I've been able to connect using a serial COM port. The Ethernet connection refused to work -> the LED on the Ethernet connector stayed OFF

When assembling the Beaglebone back to the Kiwi2 board, it no longer booted. I took some voltage measurements.

On connector P9, I find the PSU voltage between ground and VDD_5V (Pin 5/6), around 0.7 V on SYS_5V (pin 7/8)

Is there anything I shall try from this point?

Thank you for any advise

Jean-Michel

Comments

  • jksjks

    Getting a short burst of light on the power LED (the one between the Ethernet and USB connectors) when the Beagle and Kiwi boards are used together sounds like the "brownout" problem. Where a cable between power supply and Kiwi is either too long or uses too small a wire gauge such that there is momentary voltage drop dur to the large current spike at power up.

    The Beagle detects when the voltage is below about 4.75V and will refuse to power up. That's why the power LED only flashes. There is much less current drawn when the Beagle alone is used. And that's why it works.

  • F5MMXF5MMX

    Thank you for the input, I'll add a large capacitor on the cable at the connector side to see how this behaves.

    The setup was running fine during months, but maybe the PSU is now showing an issue.

  • F5MMXF5MMX

    So I tried adding a large capacitor on the connector side with no effect.

    I changed the PSU to a 5V 10A and no difference.

    Would any have an idea on what to check next?

    Many thanks

  • jksjks
    edited June 14

    Adding a large cap has its own problems. If the power supply is turned on, and the cap charged, then plugging the live power cable into the Kiwi should work. If it doesn't then it's got to be the cable length or wire gauge. You can only see the voltage droop at power on with a (triggered) scope trace or very fast multimeter. It doesn't matter how much current the power supply produces in this case. I^2R drop only depends on the current pulled by the Kiwi. Not what the source is capable of supplying.

    But if the power supply is turned on while the cap is discharged then it may also not work because the cap will cause the rise time of the 5V waveform to be too slow. The Beagle requires the 5V rise time to be 50 milliseconds or less.

  • F5MMXF5MMX

    Each time I connected the cable with power ON onto Kiwis plug and it didn't change anything in the behavior of the Beaglebone, power LED turn On for a fraction of second and turns OFF again.

    I'm feeding the Kiwi2 with a 25cm long 1mm² cable, so the effect of the power cable must be neglectable.

    What is the expected current consumption expected on the Kiwi2?

  • jksjks

    2A +/-

  • F5MMXF5MMX

    Here are some further tests I made.

    • Current consumption, is 140mA during the time the PWR LED is activated then it drops to less than 1mA
    • I disconnected the Beagle from the Kiwi2 board and used jumpers to hook the 2 units, when only GND, VDD 3V3 and VDD 5V are connected between the Beagle and Kiwi2 boards, the PWR LED turns on longer (0.1s) than when additional connections are made
    • When feeding the Beagle from P9 connector connecting GND and 5v the Beagle is exhibiting the same behavior as when it is fed through the Kiwi2 board.

    It clearly looks like the Beaglebone board is faulty. Is there a way to get a warranty replacement of the board?

  • jksjks

    Sure. Email sales@kiwisdr.nz with your details and we can ship you a new BBG.

  • ZL2LDZL2LD

    I have programmed up another Beagle and will ship it tomorrow

    F5MMX
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