Gerald: Well, in the case of the B&K 1550, set to 5.0 Volts, and any reasonable current limit, if the power supply output is turned on, and the power supply cap in the Beaglebone Black is fully discharged, then the BBB never starts. Just one blink of the power LED then nothing. On the oscilloscope, voltage rises from zero to 6 Volts in one ms, then decays back to 5.0 Volts over 100 ms. or so. Probably trips the overvoltage detect in the BBB power chip, which must be latching.
If you cycle the output off, wait about three seconds, then on, and the caps in the BBB have dropped enough to reset the BBB power chip, but not decayed all the way back to zero, then the over shoot voltage is less when you turn it back on, and the BBB will generally start on this second try. P.O.S. power supply. --- Graham == On Fri, Nov 14, 2014 at 1:39 PM, Gerald Coley <[email protected]> wrote: > I have seen it on one board. Funny thing is it does not always do it. > > Gerald > > > On Fri, Nov 14, 2014 at 11:45 AM, John Syn <[email protected]> wrote: > >> >> From: Graham <[email protected]> >> Reply-To: "[email protected]" <[email protected]> >> Date: Friday, November 14, 2014 at 8:03 AM >> To: "[email protected]" <[email protected]> >> Subject: [beagleboard] Re: Labolatory power supply fails to power up >> BeagleBone Black >> >> I have a similar problem, using a "B&K Precision 1550" Lab Bench Power >> Supply. >> When you turn on the Output of the supply, the BBB Power Light blinks >> once and >> the BeagleBone Black does not boot. >> >> If you put an oscilloscope on the output of the supply and watch it turn >> on, then >> the power supply overshoots up to 6 Volts, before returning to the 5 Volt >> setting. >> >> That is just crazy. I have never seen a bench power supply do this. >> Perhaps you should contact B&K, because there must be something wrong with >> the voltage regulation on your power supply. >> >> Regards, >> John >> >> >> >> It turns out that the Power Management IC used in the Beaglebone Black >> will >> do an over-voltage shutdown at 6 Volts for protection. So, that is why it >> does >> one-blink then shuts-off. >> >> So, not only do you need a certain rise time, which the B&K power supply >> meets, but you can not have any large overshoot. No good power supply >> should have this much overshoot, but the B&K does, so it has problems >> running a BBB. >> >> --- Graham >> >> == >> >> On Friday, November 14, 2014 4:03:37 AM UTC-6, bremenpl wrote: >>> >>> Hello there, >>> I have a very strange problem with powering up BeagleBone Black (rev >>> C).... When i try to power it up from some cheap AC adapter it works fine, >>> but when I connect to to my labolatory power supply the power LED on board >>> is lid for a second and then doesnt power up the MCU and turns off intead. >>> I have connected both supplys to osciloscope and they are both stable, the >>> laboratory one even more. Why is the power controller on the BeagleBone >>> Black refusing to power up the MCU when powered from lab supply? I have no >>> idea what is this about. I would aprichiate any help. >>> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> > > > > -- > Gerald > > [email protected] > http://beagleboard.org/ > http://circuitco.com/support/ > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/xRPC_39ju9Y/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
