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OMG under voltage
#1
Ok so I have spent a lot of time, energy and money trying to solve the dreaded under voltage notifications.. I really don't know what else to do.

I am using this power supply

https://www.automationdirect.com/adc/sho...05-dc12-40

and this usb hub

https://www.amazon.ca/gp/product/B005P2B...UTF8&psc=1

How is it possible that I still get under voltage messages? 

What other things can be done to get rid of this?

I am using a RPi3b with the moitessier hat. In the usb hub (self powered) I have a wireless keyboard/mouse dongle, o-chart dongle, touch screen and an USB to SD card reader. 

How much power does the hat use already?
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#2
Well the cable powering the Pi is a candidate perhaps. Is it powered via the micro USB or direct to the GPIO pins?

I assume you are powering the Pi from the power supply directly? (rather than via the USB hub)

If you don't connect the powered hub presumably the UV message doesn't occur?
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#3
when you are sure you are providing enough power, bad quality cables are always the candidates.
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#4
(2019-09-23, 03:25 PM)baltika_no_9 Wrote: Well the cable powering the Pi is a candidate perhaps. Is it powered via the micro USB or direct to the GPIO pins?

I assume you are powering the Pi from the power supply directly? (rather than via the USB hub)

If you don't connect the powered hub presumably the UV message doesn't occur?


Currently, I cut a usb cable and connected that to the power supply and plug into the micro usb port on the Rpi, I have just purchased shim to allow me to power to the gpio pins directly (the shim is to provide the circuit protection you get from micro usb port). 
That will eliminate the USB cable as a culprit. I hope that solves it.

No I get UV messages regardless of the hub being connected or not. Mind you I do have to plug the keyboard fob and the ocharts dongle directly into the rpi then, so maybe not a fair statement...

Thanks for your suggestion about the cable

(2019-09-23, 04:12 PM)Sailoog Wrote: when you are sure you are providing enough power, bad quality cables are always the candidates.

I will eliminate the cable and go directly to the GPIO then. Last resort!
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#5
(2019-09-23, 04:26 PM)rastam4n Wrote: Currently, I cut a usb cable and connected that to the power supply and plug into the micro usb port on the Rpi,

..............

Some USB cables are sold as "USB charging" cables. Some ordinary USB cables are fine for data but do not have thicker copper conductors to support the 2.5A or so that the Pi requires. I'd buy the biggest wire gauge USB cable and try that.

Best of luck!
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#6
(2019-09-23, 04:26 PM)rastam4n Wrote: I will eliminate the cable and go directly to the GPIO then. Last resort!

Be careful because you are avoiding some protection circuits doing this. If you power from GPIO and you accidentally power from USB too you could fried your PI.

Editing: sorry I did not read about your shim.
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#7
I've been through what you've been through and it's really frustrating. When you are absolutely sure that your power source is the right one the problem is always in the cable and its micro-usb connector.

The vast majority of USB cables are not really prepared for the large amount of power that a Rpi 3 or higher is going to demand.

Keep in mind that in a USB cable coexist 4 smaller cables for transmission of energy and data. In fact to feed the Rpi the data surplus but take space to the power so it is difficult to find normal USB cables with enough capacity to transmit that energy. In addition, often the solder to the micro-usb connector or the connector itself is not good enough.

I solved it with a 12 v-5V adapter like this that already includes its specific connector just to transmit power.

[Image: s-l1600.jpg]

Since I use it I don't have the bloody lightning icon bothering me anymore. And when I switched to a Rpi 4 I used a simple Micro-usb to USB-C adapter and it goes smoothly.

In your case the power source is good but the cable is really your problem. Using GPIO is a Plausible solution but somewhat risky as sailoog tells you. I have used it and it is functional, but if you find a suitable cable it is a better solution.

In the new Rpi 4 has moved from the micro-usb connector to USB-C precisely because the USB-C has already been designed with the aim of transmitting greater amounts of energy so that only USB-C of very poor quality give problems and the vast majority work properly.
Why are sailors more daring than other men?
Because: No man is so often afraid
like the sailors.

"Of the questions of the seafaring world", in
The Tree of Science, Ramon Llull
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#8
(2019-09-24, 10:53 AM)pinguino Wrote: I've been through what you've been through and it's really frustrating. When you are absolutely sure that your power source is the right one the problem is always in the cable and its micro-usb connector.

The vast majority of USB cables are not really prepared for the large amount of power that a Rpi 3 or higher is going to demand.

Keep in mind that in a USB cable coexist 4 smaller cables for transmission of energy and data. In fact to feed the Rpi the data surplus but take space to the power so it is difficult to find normal USB cables with enough capacity to transmit that energy. In addition, often the solder to the micro-usb connector or the connector itself is not good enough.

I solved it with a 12 v-5V adapter like this that already includes its specific connector just to transmit power.

[Image: s-l1600.jpg]

Since I use it I don't have the bloody lightning icon bothering me anymore. And when I switched to a Rpi 4 I used a simple Micro-usb to USB-C adapter and it goes smoothly.

In your case the power source is good but the cable is really your problem. Using GPIO is a Plausible solution but somewhat risky as sailoog tells you. I have used it and it is functional, but if you find a suitable cable it is a better solution.

In the new Rpi 4 has moved from the micro-usb connector to USB-C precisely because the USB-C has already been designed with the aim of transmitting greater amounts of energy so that only USB-C of very poor quality give problems and the vast majority work properly.

Interesting I have the same one but with a straight connector instead of the elbow connector.... constantly gives me UV errors. I wonder if there is something else going on... I noticed that the UV errors and flickering on my monitor is happening at the same time... The monitor people are saying I need to increase voltage which i have (from 5v to 7.5v but it still happens from time to time at the same time. 
I do have a voltage monitor on my motor it is a constant 14.1v while running ( i only use this under power - "motorboat")
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#9
Rastam4n is that in matters of electrical power supply it is necessary to calculate well the whole set. Especially in 12 V systems and long cables where the voltage drop is important if the thickness of the cable is insufficient.

If the screen and the converter pull the same line of 12 V and this is very long from the battery - more than 2 meters - and on top of that there are other equipment sucking current from the same line there are issues like those you comment. 

The fact that the screen flashes at the same time that the Rpi shows lack of voltage is a clear sign, in my opinion, that you should reinforce the main line with thicker cables or add a separate secondary line for the screen.
Why are sailors more daring than other men?
Because: No man is so often afraid
like the sailors.

"Of the questions of the seafaring world", in
The Tree of Science, Ramon Llull
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#10
I connected my Rpi to a powered USB-hub, delivering 2.4A on each usb-A-connection, via a cable like this:

[Image: 274062_61031.tif?ref=133F6CE70C&format=j...0&mode=pad]
 and then a good quality USB-A-to-micro-adapter. It works -  no more under voltage...
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