BBB RevC doesn't boot under standalone power

I’ve been using my BBB RevC just fine with it connected to my computer’s USB Host port. I finally got the bits I needed for standalone – HDMI cable, USB hub, power supply, etc.

If I plug the power in to the otherwise unconnected BBB, the power light lights, the four status lights light, then all five shut off.

If I plug the USB from the PC in to the otherwise unconnected BBB, it boots right up, normally. If I then plug in the power, there is no change. If I then unplug the USB, no change. It runs on the power dongle!

If I plug the USB from the PC in to the otherwise unconnected BBB, it boots right up, normally. If I then plug in the power, there is no change. If I then unplug the power, the BBB shuts down, even though the USB is still connected.

The power is from a wall wart – 5v nominal, 5.3v measured, 1 amp nominal.

There is no SD card installed. I bought the BBB direct from Atoms Ind. a couple weeks ago, and have not (to my knowledge) changed anything.

Any suggestions?

We have seen this before. I suggest that you try another power supply. While current is important, so it the rise time of the power supply. Try getting one with higher current rating to see if the rise time is faster. Or just ry anothe rpower supply.

Gerald

Gerald,
Thanks, another power supply does work. 5v nominal, 5.2v measured, 2.6 amps.

Although this workaround will help keep my project going, I would suggest that you pursue this as a fault of the BBB. There are behaviors documented here, and not mentioned that indicate a sensitivity to minor perturbations in power and ground that will cause problems for BBB users and those who must support the BBB. When my BBB is running with both the “faulty” power supply, and the PC USB power, and the power supply is removed, the BBB shuts down. When I turn on or off a device that is connected to the BBB (a Sherline 8760 stepper driver connected through a Zylotex DB25 cape), the BBB powers down. The “faulty” power supply was procured from a reputable equipment dealer for the purpose of running the BBB, and is in spec.

There is a problem with the BBB. It should tolerate variations in its electrical environment. As attractive as the BBB is, developers cannot wrap it in photoisolators, chokes, and paranoia.

If there is a problem with some 1 amp power supplies not having enough power moment to moment, perhaps you should specify a 2 amp power supply. Maybe you should recommend an additional capacitor be place across the power supply.

Thanks again for your quick and accurate help, and good luck with your efforts to support the BBB.

–Justin

I am already looking into this. However, the idea of adding circuitry for bad power supplies to work seems like a lot of work. Just use the right power supplies and the board works.

This is a development board. Not a board designed to work under all conditions and environments or with every cheap power supply out there. If it were, I would add the power supply to the kit and raise the price by $10. Picking a good power supply in the process.

As I said it is not about current. It is about rise time. Some power supplies limit the current in initial stage of power up and then allow the current to go up to the rated voltage. That drop in the voltage is what is causing the issue. You might try hooking a scope up the the board and take a look at the DC voltage coming out and see what it is doing.

Gerald