2.1mmバレルジャック接続9V

This was exactly what I needed to power my robot.

It's a 9v to barrel jack. What more do you need?

This product seems usefull, but it is not well assembled. After connecting it 2-3 times to a 9v battery it stopped working. Closer examination showed that the black cable had detatched itself from the battery plug.

works perfectly, now it can work without needing to be connected with a usb wire to the computer.

What more can I say