[Hagrid]

Hi All,

There has been an active discussion regarding powering Samantha from the main Tetrix/Matrix battery. The new Samantha user manual specifically advises against this with Matrix and I wanted to know why. The current season rules also strongly lean this way.

The issue is that with the Samantha connected to the primary battery, any dodginess in the earth connection to the motor controller can cause the main motor current to take an alternate route via the NXT cable to the brick and then up the USB cable to the Samantha and finally via the Samantha's power back to the battery.

After drilling down into the issue with HiTechnic/Matrix as to why this issue is specific to Matrix, they have just come back and said that it can also happen with the Tetrix controllers.

The currents involved could potentially be 10's of amps running through light gauge wires/connectors rated at a very small fraction of that current.

The result may include damaged Samantha, damaged NXT, and loss of communication events.

I am not a spokesman for FIRST FTC, Hitechnic, Matrix, or Tetrix - just a tyre-kicking mentor who doesn't like unsolved mysteries.