I’m having trouble with the DC input on my beaglebone (it works fine powered by USB).
When I use a 5V 1A adapter the power LED blinks very weak. Scope trace shows that the power supply is periodically getting dragged down and the over/under volt chip is tripping.
When I use a 5V 2A adapter the power LED blinks strongly (ethernet led also blinks). Scope trace shows noise on the power supply and the over/under volt chip tripping periodically.
I tried putting a 10u cap on the DC jack power supply pins did not seem to make a difference.
Has anyone seen anything similar?
Are these supplies regulated? 1A may not be enough if the supply is not truly 1A.
If the 5V goes too high due to a spike, the voltage trip circuit will trip for sure. I would not expect a 10uF to fix the issue if the spike is enough to trip the circuit.
What is the voltage reading on each of the supplies?
Yes, they are regulated switching supplies. They read 5.14 DC unloaded.
Do you have a particular supply you recommend. I’ll give that a shot.
The spec on the overvolt circuit shouldn’t kick in until <3.5V or >5.7 V worst case, so there should be margin…
I assume they have a three prong plug, where a earth ground reference is supplied? What else do you have plugged into the board?
No, they are both two prong (no ground). Nothing else plugged into the board. No earth ground connection.
Plug in the USB cable.
If you have the USB cable plugged in and still have iissues, make sure the power supply and PC are plugged into the same power strip.
You may need to supply an earth ground connection to the board. In some cases USB grounds may not be connected to earth ground. Overall you are better using a earth grounded power supply.
If I have the USB mini plugged into my computer AND AC connected, it boots ok. How do I tell if it is using AC power?
If I disconnect USB it immediately goes back to the flashing power LED.
Connecting the host USB doesn’t seem to help.
What is the rational behind needing an earth ground? The DC jack is just 2 pins. Are you assuming the GND on the jack is shorted to earth ground in the external transformer? I thought these are generally isolated so that earth ground does not carry any current. I just measured one on a 12V supply and it had 1K resistance, so apparently there is a path, albeit resistive …
If the USB and DC are plugged in, it uses DC power.
Sounds like the PC is supplying the ground.
USB host should have no affect.
Earth ground gives a good ground, instead of a floating ground. Depending on how the wall plug is wired and the power junction box is wired, the neutral may not provide a sufficient reference for the over voltage circuit. It can act funny if there isn’t a good earth ground on the board or the DC power.
I have 3 supplies that I've found work well with A3 and A5 bones
(and a handful of other boards) from a collection of sources. None
have an earth ground pin.
Volgen KTPS10-05020WA - 5V @ 2A
V-Infinity ETSA050360UDC-P5P-SZ - 5V @ 3.6A
Tenwei TAV02-05020000 - 5V @ 2A
At home, I have a V-Infinity EPS050260UH-P5P-SZ 5V @ 2.6A that works
well with my xM but I haven't tried it on a bone.