Labolatory power supply fails to power up BeagleBone Black

GoogleGroups
21

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

22

I have seen it on one board. Funny thing is it does not always do it.

Gerald

23

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

24

I have tested the board again and heres what I have come to:

  • Using meanwell 5V ac adapter works when the 10k resistor is NOT soldered to battery header. If theres resistor soldered, but there is no battery attached it stops working and the power led blinks all the time. It really seems that the power controller is trying to switch to the battery that is not there. After placing the battery everything works correct. I only home it wont get discharged to fast when the board is off.
25

Replace the resistor with a wire and just short it to ground.

Gerald

26

But will trhis allow battery to work properly?

27

I have observed an interesting thing now. I have replaced the resistor as you adviced. Now I can indeed use the BeagleBone Black without battery. Now when I run on a regular power supply and the battery is in and charging, when i remove the main power supply it seems like BeagleBone Black is performing a safe shutdown (im not sure im not connected to serial debug), because it doesnt automatically go off but it takes its time turn off user leds and power led. Is this made on purpose? Why didnt he act like this when there was 10k resistor instead of 0R?

28

When you remove it yes. In the meantime I am hoping this stops people from blowing up processors. If battery is needed it can be removed.

Gerald

29

And also an important thing- I cannot turn on BeagleBone Black on battery only now.

30

I can accept that. This woul be only for non battery operation.

Gerald

31

This functionality is actually very good for me. I was intending to make a system that prevents user from turning off BeagleBone Black without proper shutdown. I thought i will have to implement this in code, but since the BeagleBone Black is shutting down automatically after the main supply is down (running on the battery in that time) i dont have to do this on my own. Please correct me if I am wrong in understanding this.

32

As long as there is nothing that can cause the PMIC to shutdown before it has completed the full power up cycle we are OK. It is the sitting down before that process has completed is what concerns me.

Gerald

33

So you are saying that if I remove the main power supply while BeagleBone Black is turning on (like 7 seconds?) the safe shutdown wont occur?

I have checked some scenarios:
- Turn on BeagleBone Black with battery in and power supply. Then remove power supply before BeagleBone Black fully inits. If I do that the board wont turn off and I have to do it manualy after full init. I gues thats ok, I can check for power right after I turn on my program.

- Second scenario is turning the board on with battery in and usb cable with power in. In this case BeagleBone Black keeps resseting after 2-3 secs. Not sure whats happening here.

W dniu 2014-11-17 o 12:58, Gerald Coley pisze:

34

That all depends on the state of the current SW configuration. My focus is shutdown before SW even wakes up and has it’s first cup of coffee, before SW can make anything happen.

You first scenario is after SW has already run via the uBoot and done what it needs to do.

Per the datasheet there may be issues detecting the battery when DC and USB are connected. Check the datasheet for more information to see how it affects you.

Gerald

35

My software is supposed to be some userspace software that is turned on via script when the board is fully on. Also in the end application I dont connect power pin on ish slave connection.