Full Version: Alternate Power DC-IN on the Euler Bus also with PI filter for batt operation
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In the pic above we are looking at an alternate method of powering the PineA64 with DC-IN on the Euler Bus; +5v on pin(4), and ground ( - ) on pin(6).  

In this pic above white is common (ground) and black is 5v ( + ) the 'hot' wire.  Electrically, pin(2) and pin(4) on the Euler bus are connected to DC-IN on the micro usb power jack (see schematic pp6 of (19));  if a person is careful, either method may be used to provide 5v power to the PineA64 board.  WARNING:  do not do this if you are not sure of your skills, nor if you are unsure of the theory. Check with someone skilled before proceeding.

There are a couple of reasons why you might want to connect DC-IN with this alternate method:  1) you may want to provide your Play Box with a 5v barrel connector for charging,  2) your power supply is only rated at 2.0A (5v) and you want to shorten the supply line and bypass the weaker micro usb connector,  3) you want to make a more solid power connection perhaps with a [ toroid | cap ]  low pass filter for use in an auto  or with other dc-dc converter. 


Normally I do not recommend this method; because it has the potential for making mistakes;  only connect 5v on DC-IN, never reverse the polarity of the wiring (always check, never guess);  that said, this method does provide an alternative for routing DC-IN for those who have the skills and know what they are doing. 

WARNING:  If you're looking at the schematic(s) pp12 of (19) the 5v on pin(8) is NOT a DC-IN pin;  pin(8) is a 5v output pin only.  The only DC-IN pins are pin(2) and pin(4).  Any ground pin may be used for ground; however, pin(6) is convenient for the purpose.
Edit: added another pic.
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.

In the pic above I am powering the PineA64 with a 12v batt (3000mah, SLA) using the 'CPT Car Power Technology' DC-DC converter;  it takes input of 7v - 50v (10 Watt) and has an output of 5v @ 2000ma. 

Again, I am feeding the 5v out from the DC-DC converter through the PI  low_pass  filter;  this is important when using most DC-DC converters, because they typically produce noisy outputs.  The PI filter will reduce the noise on the DC line input to the PineA64 producing a nice clean quiet stable power source!

Note: CPT comes with a micro usb connector output; I removed the connector-- I was pleased to find a good two wire cable under the sheath and I decided to feed the power to the euler bus +5v to pin(4) and the ground wire negative to pin(6). This makes the connection 'solid' and by-passes the weak micro usb connection. This is preferred for most robotics applications.


This is the solder side of the PI filter board. The important thing to note is that it is simplicity itself. Anybody can do this !


This is a close-in of the finished PI filter.  The point to note here is the male header pins. I always build small projects like this with header pins so that setup and tear-down is easy with jumper wires; also the same component can be swapped in when needed in other projects.

Update: I added two close-in pics of the PI filter.

... again, this very much a beginner soldering project; just dive in and try it !

The full system running on 12v batt !

In this second filter I rewound the toroid inductor (doubled the windings) and moved all the pins to one side of the board, will facilitate easier mounting in the boat's weather proof case. 


The pic above is a close-in of the hand-wound toroid inductor. I pulled the inductor from an older PC planar board and removed the original 10 wrap winding.  Then, using enameled coper wire, I replaced the wrap with twenty turns; this also is very easy to do; although tedious, and maybe a little boring. Confused

Now I just need the second CPT to arrive.

This PI filter is yet another option for arranging parts swiped from an older Epson printer power supply board.  The inductor is not a torroid (as the others) and I have simplified the caps down to one on either side of the inductor.

This filter is being used to feed the Android playdesk via the euler bus, pin(4 5v+) and pin(6 ground).
I've ordered a power supply to go the Euler Bus way. Not sure if I need the filter, but in case: do you have any idea of the value of the inductor?  Shy
(09-17-2016, 08:25 PM)cr2016 Wrote: [ -> ]I've ordered a power supply to go the Euler Bus way. Not sure if I need the filter, but in case: do you have any idea of the value of the inductor?  Shy

I typically pull the components from old PC mother boards or power supplies , where they have been used for this same purpose.  The inductor, sometimes referred to as a choke, can be as high as 10H (Henrys).  Depending on the size of the caps , and the amount of ripple in the line , can be as low as a few hundred mHenrys, as well. The caps can be anywhere from 500mF to 2000mF .   Usually the inductors can be physically smaller if they are soft-iron torroids;  but, composities are also available. Of course you know if the filter is effective by putting a scope on the output.  The ripple reduction of a low-pass filter on a scope is often dramatic. The first link below is a theory link;  the next two links are calculator links which may be used to design passive filters.

Back in the day, we were filtering the 60hz or 120hz ripple from the half-wave or full-wave rectifiers. Today we're filtering the high frequencies of a switching supply, or the noise generated by an automotive dc - dc converter; or other electrical noise often picked up by a long dc power cord from a wall wart.
Thanks, I will check this out!
The power supply is supposed to arrive before mid-October. I will see how the 5V output looks like through an oscillo...
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