# Wiring design for USB voltage and current tester

With reference to this article USB Voltage and Current Tester, it shows a diagram as follows:

May I know if it is the same as the following circuit diagram:

This is because according to the article, they only use the black and red cable.

There is no mention of how should I do with the green and white cable.

If the circuit diagram is wrong, I would appreciate if someone can enlighten me the correct circuit diagram.

Thank you.

Your diagram seems correct to me. It's not the same as in the instructable. I think that your diagram makes more sense.

The instructable shows that the data wires (red and green) are cut. That means that the USB slave device under test will not be able to communicate with the host. The slave will not behave naturally, if it can't communicate. Also by the USB specification, the slave will not be able to receive more than 100mA supply current. If it the data wires are intact, the slave device will be able to behave naturally.

One more thing. Connect-through the EMI shield around the cable.

• The green and white wires are data, and are shown as not connected in the photo. Red is +5 volts, and is broken to allow connection of an ammeter. – Peter Bennett Dec 29 '14 at 5:06

The diagram is how one would be wired if the data lines were pass-thru. But in the images from the article, they aren't connected. So the diagram for the article would look more like this:

black -----[]------ black
green ---|     |--- green
white ---|     |--- white
red   ---[]   []--- red


Connecting them would allow you to use the device as a standard USB cable rather than as just a power only cable.

• Oic, so there is no harm to connect the green and white together because not only is can serve as a power only cable, it also can serve as a standard USB cable, am I right? Please enlighten. – user275517 Dec 29 '14 at 5:00