开云体育

I’m not sure there is NO noise, but there are 40 of them in use in our data network and I’ve heard no complaints. ?

They are $15 from Amazon?

and $40 for 10 of them from Alibaba.?

But I can’t figure out how to send Alibaba money.? The web page is always broken in some way late in the purchase. ?

Can anybody buy from these people??

? ?Tadd

On Jul 13, 2021, at 4:27 PM, Dave R <daverickmers@...> wrote:

We see linear supplies that waste half the power as heat and smps supplies that raise the noise floor noticeably.

Can you detect any noise from the DROK? Their website isn't very technical. Amazon is famous for selling EMI plagued devices. 73

On Tue, Jul 13, 2021, 10:21 Tadd KA2DEW in NC via <tadd=[email protected]> wrote:

The acid test for all this is whether the Raspberry PI complains about under-volt.? If the PI doesn’t complain, EVER, you are probably in great shape. ?

Measuring the voltage at the PI makes sense.? Measuring the current doesn’t help much since the PI will draw what it draws. I don’t think longer cables change how much current the Raspberry PI needs and a bigger power supply on the source end won’t change the current the Raspberry PI needs. ?

My solution is to use a 5.2v regulator and a six inch cable to the USB-c plug.? There are a host of inexpensive (< $20) variable output, 8v to 37v input, adjustable output supplies out in the world.? DROK makes a good one which actually has a variable voltage output into a USB-A socket and that’s the one our local radio club uses.? We like that the PI comes on when the radios are powered up.? Having the PI powered up whenever the radios are on is a good thing.? Having the radios powered and the PI not powered can be bad because voltage enough to start up some of the PI’s peripherals can show up on connections between the radios and those peripherals.? So if the PI is powered down and the radios are up, you can get bad glitches in the peripherals. ?

The point is, you need 5.2v at the Raspberry PI.? You can measure the voltage at the 40-pin AUX connector.? Wires drop voltage when the current draw is > 0.? Longer wires drop more voltage and higher current draw causes more voltage drop.? Thinner wires also cause higher voltage drop. ?

So, ?if you have a voltage need, and a current need, and length of wire you want to keep the voltage high enough, the length short enough and the wire thick enough. ?

? ?Tadd

On Jul 12, 2021, at 10:15 PM, dwfunk4475 <dwfunk@...> wrote:

Measure the voltage and current at your Pi, don't guess.?

And FYI, power supplies according to? require 5.1 volts.

-david

On Mon, Jul 12, 2021, 16:15 Jeremy Utley <jerutley@...> wrote:

Hi all in the group!

?

Been doing lots of Google searches, and while years ago I found this kind of info for the old micro-USB cables, I haven’t found similar information for USB-C – and I figure the Pi Ham Radio group is my best bet.

?

I’ve got a Pi-4 8GB model, with an Argon One M.2 case and Samsung SSD as the boot device.? I’m building out this device for portable logging/digital mode usage when I’m on POTA activations – either by VNC from a tablet, or a small portable screen mounted in my radio case.

?

So the problem I have is with voltage drop – I power the Pi via a PowerWerx USB-Buddy – which provides 5v DC @ 3A, connected to a Bioenno LiFePo4 battery.? In my testing here at home, using a 1ft long USB-A to USB-C cable, it works without any problems.? But, I wanted a longer cable, so I went to a 3ft cable from the same maker.? Once I used that cable, I was immediately getting low voltage warnings – so obviously I’m getting voltage drop on the longer cable.? But I’m having trouble finding heavier USB-A to USB-C cables to avoid voltage drop across that length.

?

Anybody have knowledge of any good cables that fit the bill???

?

Thanks!

?

Jeremy, NQ0M