Extend a USB charging cable using electrical wire

S

southafricanrob

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Hi,
I have installed a USB board into a shelf in my hallway so I can plug my phone in when i come home. Problem is its about 5 metres from the nearest power plug so I cut the cable and lengthened it using standard 2mm ripcord.
I ignored the white and green wires just used the black & red for GND / 5V.
Its all plugged in and my phone (micro USB) charges fine but my wife's iPhone doesn't charge (and gives 'unsupported accessory / cable' error).

Anyone know if this is because the other 2 wires aren't connected or if its some issue with the wire being too long now?
 
not sure about the cause of the problem.

could be to long a cable (happens with some printers)

the best way to lengthen USB cables beyond a certain lenght is normally done using LAN cable and special adaptors....
 
Did that cable work on the iphone before the cut it. Does the iphone charge from a normal car charger, if yes, then you have a to big voltage drop over your cable. I found some sony phones also want good volts and amps.
 
Hi yes it did - its a short little multi cable from incredible connection. I measured the voltage and get 5.06V so would think that should be sufficient. Have checked all my solder joints and that I am getting power out so not sure what the issue is. Will post again if I find the problem...
 
southafricanrob said:
Hi yes it did - its a short little multi cable from incredible connection. I measured the voltage and get 5.06V so would think that should be sufficient.
Click to expand...
No, it is a voltage without load, it will be lower under nominal load. Besides, you cut D+ and D-wires, but these pins are used for detection of the charger maximum current load. Standards are different for Samsung and iPhones, some chargers can satisfy multiple brands. See diagram (figure 5) for an example how it is done.
http://www.ti.com/lit/an/slva464e/slva464e.pdf
I summary, you need D+/D-, but to prevent voltage drop extend wires on the 230V AC side, it will always work. :)
 
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Robertvv said:
Nice pdf sa junky. I note the file is from texas instruments. Are they into cellphones?
Click to expand...
It is universal USB charger with switches to charge devices using different standards. There is a switch position to comply with USB charging specification (most of generic cellphones use it), then Samsung and Apple proprietary sulutions. Read more https://en.wikipedia.org/wiki/USB#Charging_ports

In summary you need D+/D-. :)
 
aha okay thanks makes sense - do you think extending it by using standard telephone cable will cause too much voltage drop? It has 4 cores and I have a ton of it lying around so would be great to use, however the cores look super thin. Also wondering if marginally different lengths of D+ / D- would cause an issue? I know it probably would if you try and use it for data transfer but just for regular charging?
Thanks for the info so far
 
In the charger D+/D- carry low-load static voltage - no problem.
Problem is with 5V and ground wires. Actually two problems. Resistance of 24AWG single copper telephone cable is 0.084Ohm per meter. Lets assume your extension is 5 meters long, it means voltage drop on the cable 2 x 5 x 0.084 = 0.84V when loaded with 1A. You could reduce it by using more wires in parallel. However 1A load as stated above is an average value, but inside your cellphone there is a switching mode battery charger and input capacitors are not large enough to filter load spikes. It turns your extension wire into antenna with base frequency between 50 and 300KHz with enough EMI power to violate any standards. Neighbours will hate your invention.

If you after reading this insist in extending on the low-voltage side, you should attach 1000uF low-ESR capacitor in parallel with 100nF ceramic one's at the end of the cable.

It is why in my first post I suggested extending on the 230V AC side. However you mustn't use telephone wire, isolation is not rated so high.
 
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Thanks sajunky - I've always struggled to get to grips with electricity and you've shown me I'm a lost cause;-) Will definitely go the extending the 230V route - I can mount the charger inside the shelf anyway and make it just as neat. Thanks again
 
Robertvv said:
Nice pdf sa junky. I note the file is from texas instruments. Are they into cellphones?
Click to expand...

Ti have for many years made chipsets for mobile.

In any case, I did all the R&D earlier this year to be able to charge anything including Apple, from a battery
 
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