For a robotics application, I'd like to power some external electronics and sensors off the logic circuit in a robot arm.
The components are a computer (19V, 65W => 5A), 2 cameras (1.2A), 1 light (0.35A), USB2.0 I/O board, and power board. All this on top of current draw from the motor logic, which runs off a 4.3A power supply atm. Therefore, I estimate the upper bound to be 12A.
The logic power runs through an 18 gauge wire. According to this table, 18 gauge permits either 16A as chassis wiring, or 2.3A as power transmission.
Note the robot arm is roughly 0.6m long; obviously, because the logic power runs internally, the wire length is greater than 0.6m.
Will I be able to power my electronics from logic power?
I am willing to test my system empirically.
(BTW, as a CS major, I have zero experience with electronics.)
Best Answer
Three things of note:
The AWG guidelines are very CYA. It says 16A, but that's probably anywhere from 60% to 90% of what it can actually handle.
Multiple 18 gauge wires tied together will have a lower (derated) capacity than a single 18 gauge wire. And in a pipe less than in free air.
But the biggest thing is really your application! Length is minimal, probably 1 meter (plus return path, so 2 meters), so the wire resistance is minimal, which means very little voltage droop.
But how many power wires are there? Is each motor individually cabled?
Is the full amperage running the full length of the cables? Is the 5 Amps for the computer actually going over the arm, or is it at the base? Can it be individually powered?
What duty cycle is to be expected? How often are the motors going to be on? How long will the entire setup be on?
For the most part, you need a wiring schematic. A plan on how everything is connected. Without that, you cannot really know what you need in terms of wire size. A schematic for the robot arm would be the best place to start.