Milliways wrote: ↑
Wed Aug 30, 2017 4:33 am
The first challenge is finding a µUSB socket to terminate the cable, but assuming you can find one solder a 5Ω 5W (or greater) resistor to the power pins.
Apply 5V to the cable, and measure the voltage across the resistor.)
Ok - so I went home last night via Maplins and have the closest I could find: 5.6Ω 10W wirewound, which together with the 5.31v supply I'll use should draw about 0.95A - which is pretty close to the 1A of 5Ω at 5V
I also asked for a 4.7Ω (4R7) one...which when I got home I discovered was a 4.7KΩ (4K7)...not so useful...
1) Solder the resistor across the micro-usb socket "+" & ground (I have a break-out board I can do this on)
2) Plug USB lead into PSU
2) Measure voltage across the resistor under load.
Results from initial lunchtime test using the 5.3v (unloaded) 3A Liteon branded supply:
1) Resistor starts to get warm fairly fast. Not surprising as it's trying to dissipate quite a lot of power
2) Voltage across the load on cheap and nasty lead is identical to when using my nice thick Volutz cables.
Hmmm. Will try again with a range of cables later.
I wonder if the traces on the micro-usb break-out board could be the limiting factor here. They look pretty small.