[arm-allstar] One of two USB URIs dropping off

Randy Neals randy at neals.ca
Sun Jan 13 20:11:00 EST 2019

To close out this thread with the solution.....

1. We were using DC to DC converters with a micro USB plug on the output.
Similar to these from Amazon. https://www.amazon.com/dp/B00KKI4C1U

2. There was also a "warbling" in the repeater audio which we did not
immediately notice, but which became apparent later.

3. Another ham had a different brand DC DC converter, similarly
We connected that and after a few minutes we had a low voltage error.

4. We substituted a generic 5V AC wall-wart power supply, and the repeater
has been running steady for more than 12 hours at this point.
There is no warbling in the audio and no low voltage errors being recorded.

We obviously had a low-voltage condition on the Raspberry Pi. I did not
believe that was likely given that it used to work fine, and trying
different power supplies didn't seem to make a difference.
The voltage was drooping to lower than 4.6V at the input to the Pi Volt
The CM108 in the DMK URI has a 4.5 to 5.5 volts operating range. The low
voltage on the Pi would be even lower by the time it extended across the
USB cable to CM108 in the URI.
Voltage supplying the URI/CM108 likely sagged to <4.5V and we lost the URI.


On Sat, Jan 12, 2019 at 7:11 PM "David McGough via ARM-allstar" <
arm-allstar at hamvoip.org> wrote:

> Hi Mark,
> Yes, that style power supply is available from many sources. And, it's
> becoming the "preferred" variety for me, too, at this point.
> At least if it's not potted in epoxy, the manufacturer can't hide what
> components were used!
> I've also soldered power wiring to all my production RPi boards. I don't
> use the micro-usb at all.
> 73, David KB4FXC
> On Sat, 12 Jan 2019, "Mark G Thomas via ARM-allstar" wrote:
> > Hi,
> >
> > I use these cheap tiny adjustable DC-DC supplies, just a couple dollars
> each on eBay, fed with 12-14 VDC. So long as your 5V wires are short and
> heavy to minimize resistance and hence variation with load to the Pi, you
> can then adjust the supply up to sufficient voltage (possibly as high as
> 5.2-5.4 – I should measure...) that you measure 5.0 or 5.1 volts on the
> test point directly on the Pi PCB. Google for where exactly to measure.
> There is a poly fuse and maybe other sources of voltage drop on the Pi;
> hence the need to use a greater than 5V supply, especially on the more
> power hungry 3B+! This works great!
> >
> > My experience was the fixed voltage epoxy potted 12V-5V converters are
> too low voltage an output when under load, considering the resistive loss
> of the 3B+ setup.
> >
> > KC3DRE
> >
> > Mark G Thomas
> >
> > I am not sure if the photos will make it:
> >
> >
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