Am Sun, 03 Feb 2019 18:42:52 +0000 schrieb Martin Gregorie:

> On Sun, 03 Feb 2019 17:30:20 +0000, Markus Robert Kessler wrote:
>
>> I am using such a device
>>
>>     https://www.amazon.com/PowerJive-Voltage-Multimeter-chargers-
> capacity/
>> dp/B013FANC9W
>>
>> between power supply out and raspberry power in.
>>
> But where is it in relation to the power cable?
>
> Since it has regular sockets I'm guessing you've connected
>
> Wall      Power plug ---> supply -> Powerjive --cable to RPi--> Pi 3B
>
> in which its (correctly) showing that the PSU is giving 5.01 volts but
> will not see any voltage drop in the cable connecting it to the RPi.
>
> This is the cable that people ate telling you to check or just replace.
>
> To measure the voltage into to the RPi you need to put the meter between
> the cable and the RPi but, as this uses microUSB connectors which the
> Powerjive does not have, you'd also need USB B -> microUSB adapters on
> either side of the PowerJive. Since yoyu don't mention them, I assume
> you don't have any.
>
>
>> So, I see exactly what RPi gets. With the same voltmeter I then checked
>> the (2 out of 4) USB ports on the RPi.
>>
> Nope - because you are ignoring voltage drop in the cable.
>
>> The funny thing is, meanwhile I found a power supply which was part of
>> a "Raspberry 2 starter kit" from Vilros. This one delivers 5V and 2A
>> also,
>> but in reality, there are 5.37 Volts without load, measured with the
>> device above.
>>
> Thats quite normal. Many PSUs show an overvoltage when only tiny
> currents are being output. Even pulling 100 mA from such a PSU will
> reduce its output voltage to under 5.1v

Hi,

yes, you're right, the voltmeter comes directly behind the power supply.
But, the cable I use is tested to have around 0.1 .. 0.2 Ohms.

B.t.w., is there an upper limit, what RPis tolerate as input voltage?

At least one of my USB power supplies has an open circuit voltage of 5.5
V. Where's the limit, where damages may occur?

Best regards,

Markus

--
Please reply to group only.
For private email please use http://www.dipl-ing-kessler.de/email.htm

--- SoupGate-Win32 v1.05