Just sharing

[rahlquist]

So the question is do these cheap devices help with Pine64 power metering of not?

Yes they will give you valuable information. It's not a perfect situation is all. If you want me to get really long winded I can.

[frewind]

So the question is do these cheap devices help with Pine64 power metering of not?

Yes they will give you valuable information. It's not a perfect situation is all. If you want me to get really long winded I can.

Personally I would like the "long winded" version, as I may learn something that I can put to good use another time. I think that one of the great things about a forum like this you get to learn things from people who really do know there stuff...

[rahlquist]

Personally I would like the "long winded" version, as I may learn something that I can put to good use another time. I think that one of the great things about a forum like this you get to learn things from people who really do know there stuff...

Ok, really long winded diatribe coming up. The tl;dr version is; conductors are imperfect, copper is expensive, cheaper copper with more impurities is cheaper and has higher resistance. Every added connection increases loss as well. Micro USB connectors are as far as I can find are only rated at 1.8A.

Basically every cable and every monitoring device we add to the chain will lower the voltage and increase the current requirement from the power supply. Part of what tkaiser was referring to was those USB meters are not the last piece in the chain in 99% of all cases. Therefore they give you the value up to their output, what happens from their output to your device.....

Let me throw some more info on the table. tkaiser recommends 20awg wire whenever possible though that is nearly impossible to find in usb cables and even the dupont connector style jumpers used to connect to the pins on the Pine. Why such heavy gauge wire, less resistance. 

A 3 foot 28awg cable (typical cheap microusb cable) At 5.00v in and 2A at the end of a 3 foot cable could drop as much as 0.78v. MAninging you are working with just 4.22v, something that the Pine wont even boot with. Increase the wire guage to 20awg and you lower the drop to 0.12v. giving you 4.88v to work with. Now these numbers are a tad on the high side for the drops, (i.e. they are saying the wire is too resistive but you get the point. So if my usb meter drops it to 4.95 and my cable adds another voltage drop its cumulative. Now if at the end of that cable I hook another meter I can see the drop over that cable and asses if the cable is crap or quality. 



http://www.calculator.net/voltage-drop-calculator.html will let you do some of your own calcs to see the drops

[tllim]

Personally I would like the "long winded" version, as I may learn something that I can put to good use another time. I think that one of the great things about a forum like this you get to learn things from people who really do know there stuff...

Ok, really long winded diatribe coming up. The tl;dr version is; conductors are imperfect, copper is expensive, cheaper copper with more impurities is cheaper and has higher resistance. Every added connection increases loss as well. Micro USB connectors are as far as I can find are only rated at 1.8A.

Basically every cable and every monitoring device we add to the chain will lower the voltage and increase the current requirement from the power supply. Part of what tkaiser was referring to was those USB meters are not the last piece in the chain in 99% of all cases. Therefore they give you the value up to their output, what happens from their output to your device.....

Let me throw some more info on the table. tkaiser recommends 20awg wire whenever possible though that is nearly impossible to find in usb cables and even the dupont connector style jumpers used to connect to the pins on the Pine. Why such heavy gauge wire, less resistance. 

A 3 foot 28awg cable (typical cheap microusb cable) At 5.00v in and 2A at the end of a 3 foot cable could drop as much as 0.78v. MAninging you are working with just 4.22v, something that the Pine wont even boot with. Increase the wire guage to 20awg and you lower the drop to 0.12v. giving you 4.88v to work with. Now these numbers are a tad on the high side for the drops, (i.e. they are saying the wire is too resistive but you get the point. So if my usb meter drops it to 4.95 and my cable adds another voltage drop its cumulative. Now if at the end of that cable I hook another meter I can see the drop over that cable and asses if the cable is crap or quality. 



http://www.calculator.net/voltage-drop-calculator.html will let you do some of your own calcs to see the drops

There are a lot of AWG 20 microUSB power only cable available on Amazon, here is one: http://www.amazon.com/PortaPow-Micro-USB...power+only

The microUSB cable that Pine64 online store carry also is AWG 20 type.