Alternate Power DC-IN on the Euler Bus also with PI filter for batt operation

[MarkHaysHarris777]

Addendum:  PI  low_pass  filter:

   

This little device pictured above has been discussed on the forum (and the irc channel) often enough that it warrants further explanation and an hour of my time this afternoon.  This is called a low-pass or PI filter (PI because of the shape the schematic makes). The device cleans up noisy DC line voltage by 'passing' the DC voltage and blocking the noise (RF signals, dc-dc converter noise, automobile noise, &c).  This little filter can take a 100mv ripple in the DC line voltage and quiet it down to less than 10mv literally. It is a passive circuit, requires no energy (very little), and is relatively easy to build, even by novice EE maker types. 

All four capacitors are 6.3v 1000mf caps (taken from an old PC planar board) and the toroid inductor is also a very common PC planar board inductor (in fact, these components were pulled off an old ACER planar this afternoon, and were themselves used there as a low-pass filter!)    ( they live again... isn't resurrection marvelous ! )

This device is particularly handy if your DC power cord is very long, if you live in an area with high electrical noise or radio towers, or if you plan to put your PineA64 in your automobile.