I have a hypothetical project in mind I would like to pursue but wanted to ask this before sinking too much time into it. That being having multiple SPI slaves connected to a Pi Zero. From what I've read here(Raspberry Pi Power Limitations) the Pi Zero is the simplest and safest board because "the use of a power safety diode is probably superfluous, as the Zero does not have one, or indeed any protection circuitry." Not really to sure what that is, but besides, it is also the lowest power consuming board of the Pi family which suites me regardless.
So let's say I have a 5V 8A PSU powering the Zero through the 5V pin, and then attached 6 Arduino Nano's over SPI. These Nano's would also be powered via their own 5V pins from the Pi's other 5V pin.
On a normal 2.5A micro-USB charger for the Pi Zero, 0.5A could be allocated to the Pi Zero, and then 1A each to 2 Nano's. This configuration should be within the Pi's normal design considerations. But with a 7-8A PSU supplying the Pi and 6 x 1A Nano's(30W), I was wondering if this would cross a point where the traces would potentially melt down?
I couldn't find a specific answer for this anywhere. What is the maximum Watt limit of the copper traces, or the 5V pin, before they melt?
Another solution would just be to power Pi and each Nano in parallel from the PSU instead of powering the Nano's downstream of the Pi. But once I started wondering about the max wattage of the traces I was curious if anyone knew?