9x9 Green LED Panel help.

Discussion in 'The Projects Forum' started by MorpheneGaming, Jun 8, 2013.

  1. MorpheneGaming

    Thread Starter New Member

    Jun 8, 2013
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    Hello, I just recently registered on the forums, so first of all, Hi there! Now to my question. I am making a 9x9 Green LED panel for a project. I do not know anything at all about electronics(The bad news) but I have the necessary tools to do the project. Goal: Make a 9x9 LED panel that pulses to the beat of music.

    For the LEDs to flash to the music I am using a Tip31 transistor. I already made a working small version with 3 leds, each one in parallel with a 9v battery, but no resistors on them. I used the LED parallel calculator i found on the internet but i dont know how many batteries to use and also I dont know if this mockup I made would work.

    The 9v batteries are the rectangular ones found in clocks, radios, etc. I found the image of the original LED Music schematic and combined it with the Calculator image. This is meant to be portable so any advice whether it will work or not is appreciated. The LEDS are 3.0-3.2 VF, IF:20mA

    [​IMG]
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Getting 180mA out of a 9V battery will be a challenge. The voltage will soon sag.

    You may want to consider sacrificing a tiny amount of brightness in exchange for longer LED life - by dropping the current from 20mA to 10-15mA. This would also help the battery issue.

    The base-emitter circuit of the TIP31 is a low impedance and might be too much of a load on your sound source.
     
  3. MorpheneGaming

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    Jun 8, 2013
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  4. Shagas

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    May 13, 2013
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    The way you want to power your project is a very bad idea In my opinion.
    First of all a 9volt battery will most likely not give you 180ma. The voltage will drop and you will get alot of power loss inside the batteries themselves .You would have to have 4 pairs of parallel 9 volt batteries connected in series so In total 8 nine volts batteries for this to work practically, and still that would be quite a bit of drain for the batteries and they would run out after 60-180 minutes (I didn't actually do the math , it's just a rough estimate)
    .
    The more practical solution imo (since this is a pulsating panel which is going to be stationary) is to put less of those leds in series and more in parallel (So you don't need such a high voltage power supply ) and find youself a 14,16 or 18 volt wall-wart (power supply which provides 500+mA on the output) and use that to power your project because if you build it and use it often you will spend a fortune in 9 volt batteries which will **** you off and you will want to redesign it which will lead to what I wrote above so you might aswell just do it like this straight away.

    But that's just my opinion based on personal experience

    Also regardless of which power supply method you choose , i'd put a high capacity ,say about 200-1000uf 50 volt electrolytic capacitor accros the power supply . Just negative to the negative terminal and positive to the positive terminal . This will improve the response
    Also , as Wayneh said; Don't aim for 20ma going through the leds . Go for 15-18 ma or even less. There is not THAT much diffrence in brightness , try it yourself
     
    Last edited: Jun 8, 2013
  5. MorpheneGaming

    Thread Starter New Member

    Jun 8, 2013
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    Im new to electronics, so here are my questions in regards to reading your response, 1)Its not stationary, its gonna be portable. So how would i go about in doing this then? 2) I need it to be 9x9 exactly so how would i make them more in parallel without messing up the 9x9 design?
     
  6. Shagas

    Active Member

    May 13, 2013
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    Heh connecting them in in a different arrangement doesn't mean that their position has to be altered :) Think about it. ( you almost got me on that one btw)


    Well if you wan't it to be portable then you will need them batteries.
    In that case Either use eight 9volt batteries connected 4 in series 2 in parallel
    if you want to stick with your arrangement .

    What I would do though is use a rechargeable battery , something more powerfull .Li-ion or Nicd/Nimh (these are more practical) and depending on what voltage you can get , i'd arrange the led's in series and parallel .
    So if you find for example an 12volt rechargeable battery then you could use 3-4 led's in series in however many parallel strips that comes out to be .
    Keep in mind tat 81 is a prime number and you will have 1 led that is singled out , you will just have to calculate a separete resistor value for it.

    All this might seem tedious and complicated but it's up to you if you wan't to waste 10 quid on 9volt batteries every time you listen to music with it.
    If you are doing it only for show though then go with the eight nine volt batteries (the wiring will be waaaay simpler)
     
  7. MorpheneGaming

    Thread Starter New Member

    Jun 8, 2013
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    Alright so to finish this off, and a huge thanks to all of you, say i bought this http://www.amazon.com/HitLights-BATTERY3600-Rechargeable-3800mAh-Connector/dp/B007RQW5WG/ref=sr_1_3?ie=UTF8&qid=1370735654&sr=8-3&keywords=12+volt+lithium+ion+battery battery, would that work? and say i have the leds (3 in series) then those in parallel, would i just cut the cord to expose the wires where then i would just hook em up at the ends of the panel to complete the circuit, like the diagram pic that was in my first post?
     
  8. Shagas

    Active Member

    May 13, 2013
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    Yes it would work.

    But first ask yourself:
    Is this project just for show where you will turn it on once a week for 5 minutes to show your friends or will you use it with music everyday?
    If you will use it for show then just go along with those eight nine volt batteries because it would make everything much more easier and it would not be worth the effort.

    If you are planning on using it longterm then I suggest getting that Li-ion pack .
    Keep in mind that it will take out a good 3-6 hours to wire it all up (if you are as slow as I am) . Also you will need to recalculate those resistors but that's really easy and we can assist if you don't know how to.

    Also when you finish the project and like it then you can expand//improve the input circuit with few components to make it even sexier

    Anyway I just came from a night out and am off to watch a movie , I'll drop in tomorrow
     
  9. MorpheneGaming

    Thread Starter New Member

    Jun 8, 2013
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    Its more of a one time thing, like once in a July Event im attending and Halloween basically, but during those times i will be playing a music concert song thing thats 45 min in length. and plus, i saw that the 12 pack of 9v cost 18 dollars on amazon which is a bit more than half of the battery pack
     
  10. Shagas

    Active Member

    May 13, 2013
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    If it's a one time thing the definately go with the 9 Volt batteries .
    Use 470 ohm resistors instead of the 380 and put a capacitor across the positive and negative terminals as I described but that's not completely necessary .
    Build it and test it out, post results
     
    Last edited: Jun 9, 2013
  11. wayneh

    Expert

    Sep 9, 2010
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    Do you really want to say that? :p
     
  12. wayneh

    Expert

    Sep 9, 2010
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    That's fine but if you were responding to my earlier comment, that's a moot point. My concern is that the transistor looks a lot like a short to the audio source. If the amp in that device can tolerate a low impedance load like, say, an 8Ω speaker, it may be fine.

    Redesigning your wiring for a 12V DC supply makes good sense, IMHO. It's more complicated initially but in the long run it will be much easier to find 12V sources and your light square will be more versatile and less frustrating. Don't forget that connecting batteries in series opens the possibility of a bad connection at every junction. I think 4 9V in series would just be asking for trouble.

    The trouble with using a lower voltage is that you need 3 times more current (since you'll probably have ten strings of 3 LEDs in series). That means a higher mAh rating for a given length of operation. But compared to a 9V, it'll be easy to get more juice.
     
  13. Shagas

    Active Member

    May 13, 2013
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    I had come back from a night out drinking last night so I can be excused for saying that 81 is a prime number :D
     
    Last edited: Jun 9, 2013
  14. MorpheneGaming

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    Jun 8, 2013
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  15. wayneh

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    Sep 9, 2010
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    Looks good to me.
     
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