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DIY 5V/3A power supply

Started by Jojo, February 04, 2014, 08:36:24 am

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Jojo

February 04, 2014, 08:36:24 am Last Edit: April 02, 2014, 03:12:27 am by Jojo
Hello there,

last week, I have bought a 2,5" SATA drive for my CB2. As I plugged it in, I saw that my current PSU strong enough to power the CPU, but it was to weak to power up the HDD.
Because it was already saturday evening, I was unable to go out to buy a new PSU.
So I searched through my spare part cooking boxes, but I just found a 12V/2A PSU. But waht is this?! I also found some integrated switching mode step-down voltage converters:
http://www.ti.com/lit/ds/symlink/lm2596.pdf

And suddenly the neccessary external components (schottky diode, capacitors inductors and resistors) came across  ;) :D !

The result of the weekend was a nicely working and quite strong combination of the 12V/2A PSU and a completly new 5V/3A PCB  8) .

Note:
- the very special high performance heatsink ;)
- I know that the PCB is "not beautyful". Please don't tell me things about 45 degree wires ;) .
- I know that the efficiency is not so good. But I prefere to have a working PSU then NOT to have a PSU ;) ...

Cheers!


Don't think that anyone will take more pains for his answer, as you took for your question.

Jojo

February 04, 2014, 08:37:38 am #1 Last Edit: April 02, 2014, 03:12:54 am by Jojo
Bottom layer:
Don't think that anyone will take more pains for his answer, as you took for your question.

ahrovan

February 04, 2014, 09:16:38 am #2 Last Edit: March 31, 2014, 02:51:05 pm by ahrovan
Excellent , "jojo"  8) my PCB is ::

if you Desire for modify your PCB file - and share your project Notify me  8) en.bir-robotic.ir

Jojo

Yes, of course  :) . I will uploud the eagle files, when I am back home.

Btw: nice PCB, what you have there. Looks like a little bit more then just a tiny DC/DC converter ;) ! Some kind of baseboard... nice!
Don't think that anyone will take more pains for his answer, as you took for your question.

ahrovan

*) This board have VGA-Output For but of Screen 0 and 1,and Convert I/O Pins's from 2mm to 2.54mm for More easily connect to other device's.and onboard 8Mhz processor for Additional Work and so ...
I will upload more details about BaseBoard on BRG next week's .
*) I waiting for your tutorial and share with your name on BRG.  ;)

Jojo

February 04, 2014, 03:04:39 pm #5 Last Edit: March 05, 2014, 09:48:31 am by lawrence
Hello,

here is the eagle project of my PSU. The PCB was made by the so called (in Germany) "toner transfer method".

I give only a short overview about this method:
1. This method transfers the printout of a laser printer to the copper side of the board by heat and pressure of a flat iron.
2. Then you remove the rest of the carrier paper with warm soapy water.
3. After that you can etch the layout. The copper of your circuit will be saved by the toner.
4. When etching is finished, you remove the toner from the remaining copper with acetone.
5. Solder the components
6. Finish 8) .
If you want to learn more about this, there are good tutorials in the net. Please have a look there...

About my circuit:
- I tried to keep it "universal". You can use it for all switching regulators, that are pin compatible with the LM2596 (like LM2576, etc...).
- What many people don't think about: the "fixed voltage" versions are adjustable, too (with just a voltage divider at the feedback pin)! Thats why a have put a potentiometer on my board. I have set my output voltage to 5,2V with the 5V converter version ;) .
- The board also supports different types of inductors. I have drilling holes for horizontal open core inductors, vertical open core inductors and vertical toroid core inductors. Of course other types may also be ok :) .
- The converter is put right at the edge of the board to have enough room for a heatsink.
- Measuring the output voltage with a oscilloscope showed, that there is only very low rippel and no switching peaks.
- The attatchment also includes a PDF, for those who don't use eagle. Scaling is 1:1. Print out and have fun 8) .

If you have questions, please ask :) .

Cheers!
Don't think that anyone will take more pains for his answer, as you took for your question.

ahrovan

February 05, 2014, 06:19:44 am #6 Last Edit: March 31, 2014, 02:52:33 pm by ahrovan
Thanks a lot http://en.bir-robotic.ir/?p=98
plz give your Name - Instead "jojo" -  :D
when you modify or - improve your project - I will give you User/Pass for Edit http://en.bir-robotic.ir/?p=98

diogoc

Jojo just a note.
Put some solder on the unused holes because the tracks are very thin in this point and may not withstand the 3A  ;)

Jojo

Hell yeah, you are right  :o ! I didn't see it, thank you! That is quite tricky to see, because two of the drillings don't make any trouble in my setup. But the other two...
I will fix it :)

Cheers
Don't think that anyone will take more pains for his answer, as you took for your question.

putyn

Hey, a few days ago i got my cubietruck and i need to build something similar but i wanted to ask if you measured the efficiency and the current drawn from your 12V powers supply for 5V@3A output

Thanks,
Vlad


Jojo

Hi and sorry for the late response!

No, I have not measured the efficiency, yet. But: the losses in the diode can be seen as constant, the losses in the inductor are neglictable. The Most significant losses are in the switching regulator. According to the datasheet (link above), the efficiency is somwhere between 76% and 82%. Not sooo good, but good enough for my needs :) .

Greetings
Don't think that anyone will take more pains for his answer, as you took for your question.

Jojo

Update:

don't worry, nothing burned up, nobody harmed ;) .

But: it seems that my selfmade PSU is not strong enough to power my SATA HDD AND my USB HDD. Both need something between 0,7A and 1,1A. Normally, the 3A from the PSU should be enough, but I recognized a significant voltage drop from the PSU (5,2V) to the Cubieboard's ports (only 4,8V  :o ), when I connect both HDDs. I guess that this voltage drop is mainly over the fuse (seen that before). But I have to make some tests... Maybe I replace the fuse with a stronger one or just a piece of copper ;) ... Driving only one of them is no problem. I have to investigate that...
Don't think that anyone will take more pains for his answer, as you took for your question.

Jojo

April 02, 2014, 03:03:50 am #13 Last Edit: April 02, 2014, 03:14:35 am by Jojo
Update:

I did some modifications:

  • set the voltage of my PSU from 5,1V to 5,3V

  • put another 2A fuse in parallel to the original SMD 2A fuse

  • shortened the supply wires by 50%



Now my CB2 works with SATA HDD AND USB HDD  8) 8) 8)

And: re-uploaded the pictures! Thanks to ahrovan for publishing them, because I have lost the original ones somehow  :'(  :o ...
Cheers
Don't think that anyone will take more pains for his answer, as you took for your question.