Diodes Help Needed

Discussion in 'General Electronics Chat' started by Guest3123, Nov 11, 2014.

  1. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    Working with Solar Panels. Working with Discharging AA & 18650 Batteries.

    I just heard on a video that this guy used some diodes to ballance the discharge..

    I don't understand what he's talking about.

    I know that Diodes will allow electricity to flow in only one direction, as long as the forward voltage rating isn't passed.

    This video is where I just heard it from. 02:25 he starts talking about it.
     
  2. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    I'm also aware of, and currently awaiting Buck, Boost, and SEPIC Converters from eBay. I only bought from eBay sellers that had 99.0% & mostly 99.9% & 100.0% Positive Feedback rating. Didn't want to spend my money on these Chinese devices, even though there's an extremely lot of videos on these devices on YouTube. :)
     
  3. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    Here's some images of my Laptop Power Supply. Mainly for me to keep another record of them, etc. etc.

    It's a Lenovo IdeaPad Y570 w/Intel Quad Core i7-2670QM & NVidia GeForce GT 555M, also known as My First i7 Laptop I ever & currently own. :)


    THE LAPTOP PIN CONFIGURATION : 1896984_10202857749833273_7324318362867607001_n.jpg
    THE BATTERY : 10431417_10202857749473264_4096741282929230295_o.jpg
    THE AC to DC Power Supply : 10754686_10202857671551316_1542520815_o.jpg
     
  4. wayneh

    Expert

    Sep 9, 2010
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    It's called "OR"ing power sources together. "Or" as in either one or another. The diode prevents power flowing from one power source into another. Power can only flow into the load.

    It's a great trick but it does waste energy. Every diode has a voltage drop, about 0.65V for a regular silicon diode and ~0.4V for a schottky diode. At low voltages, this drop can represent a significant portion of the total. For instance, losing 0.65V off a 6.5V supply is a 10% loss of power. The loss is relatively trivial if you're up over 12V.
     
  5. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    Awesome. So basically like this then..?

    Drew this up in InkScape 0.48.4 r9939.. Is this right?
    IMG00000001 2014.11.11 06.57.11 PM.jpg



    I also bought some (20x) SchottKy Diodes yesterday, if I was going to be messing with Solar Panels and the crap load of Boost, Buck & SEPIC Converters.
    These are the diodes I purchased from Mouser.. Only $0.19 ea. I wanted ones with lower voltage drop, but these were the lowest I could find (0.5 VFD)
    IMG00000001 2014.11.11 07.03.00 PM.jpg
     
  6. ISB123

    Well-Known Member

    May 21, 2014
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    You should download free schematic/pcb software since its going to be faster then vector programs.
    Something like Designspark or KiCad.
     
  7. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    Like Circuit Wizard?
     
  8. ISB123

    Well-Known Member

    May 21, 2014
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    Yes except those 2 I wrote are free and have huge amounts of parts for use.
     
  9. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    I usually shop at Mouser, are the parts form Mouser available in there? I tried a circuit simulation type program before, I think it wasn't free. A friend got it for me. I forget what it was called, something spice, idk.

    Ok, found the DesignSpark website.. but I don't know where the download page is..
     
  10. ISB123

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    May 21, 2014
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  11. Guest3123

    Thread Starter Member

    Oct 28, 2014
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  12. wayneh

    Expert

    Sep 9, 2010
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    The upper left diodes don't point the right direction.

    I've never seen diodes placed between cells like that, although I can see how it would protect them under extreme conditions. The "OR"ing I referred to is just one diode per power source seen by the load.
     
  13. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    They sent it right to me E-Mail.. That was really fast. The Software asked me if I wanted to go to the website to activate the software.. I clicked the button, and volla.
     
  14. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    I see what your talking about.. Here.. Hows this..?

    IMG00000001 2014.11.11 08.55.11 PM.jpg
     
  15. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    Ok.. hows this..?

    IMG00000001 2014.11.11 09.31.59 PM.jpg

    That's kinda stupid.. yeah, it protects each cell, but it taxes each one 0.5vdc.

    So basically, each cell is not 1.5Vdc, it's actually 1.0Vdc or less..

    So.. I should just put only one Schottky Diode on the positive.

    IMG00000001 2014.11.11 09.39.41 PM.jpg
     
    Last edited: Nov 11, 2014
  16. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    Or...


    IMG00000001 2014.11.11 09.50.54 PM.jpg
     
  17. wayneh

    Expert

    Sep 9, 2010
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    Looks better to me. It IS possible for one cell in series to be overpowered by the others, and eliminating the diodes eliminates protection against that, but leaving them in wastes a lot of power.
     
    Guest3123 likes this.
  18. Guest3123

    Thread Starter Member

    Oct 28, 2014
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    Kinda screwed no matter what I do huh.. I must of searched Mouser for like an hour looking for the perfect Schottky diode. Trying to find the right Schottky diode without going under my current limit I wanted to work with, (1.0A), but didn't want to get a 1.0A one, just wanted to be safe, so I went for the 2A ones. Then there's the Vfd. I heard somewhere that the Schottky diodes were really good with Foward voltage drop, so those were mainly the ones I was looking at. So.. 0.5Vdc was the best I could find. If you know of any other ones, besides the fact that I already have 20 of em on the way, it be nice to see if there's ones that have a much lower voltage drop. I totally got the hang of this whole protecting circuits from reverse voltage. I'm mainly going to be messing with 4.5v @ 1.5watt @ 0.300mA Solar cells. Got like 3 of em coming by Saturday. Messing with charging cellphones and etc. wtih Boost, Buck & SEPIC Converters (boost & buck comb.)
     
  19. ISB123

    Well-Known Member

    May 21, 2014
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    You won't find anything better than that.
    0,2fVd diodes are generally SMD and have 0,2A max. Current.
     
  20. wayneh

    Expert

    Sep 9, 2010
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    I just bought some SB140 Schottkys and was surprised to see only about 200mV drop shown by my multimeter's diode test function. Does the ∆V of a Schottky change more with current than the silicon ones do?
     
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