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Car Speaker LEDS

Discussion in 'LEDs and Optoelectronics' started by cjohnb, Apr 23, 2013.

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  1. cjohnb

    cjohnb

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    Apr 23, 2013
    This post is not so much as I need help as much as it is asking if this is ok...
    So just to go ahead and clarify my LEDS ARE LIGHTING UP TO THE BASS PERFECTLY.

    Materials: NPN TIP31C Transistor, 12V LED STRIP

    First of all let me explain my circuit. I have a wire running from my car battery to my LED strip(12V strip) and then my led strip runs to the Collector lead of the TIP31C transistor. The base lead is attached to the negative terminal of the stereo front left speaker. The emitter is wired to the positive lead of the front left speaker.

    Could this layout hurt my car radio? If so what should I do to fix it? I tried connecting the Car GND and the Front Left Speaker negative terminal to the base together, but then all my speakers refused to play music. Why is this? And if it is working fine should I ignore this?

    Note my speakers are now making a weird noise when the bass hits hard. I think they were already about to bust, but would you say my circuit is causing the weird noise or are they busted? And if busted did my circuit do it? And if so how can I fix this when I get my new speakers? Note: My speakers were already slightly going out. Also for further info:

    I drive a ford explorer 1999 model with the speakers that came with it.
    I think they are 4ohms 25 Watt
    Thanks for reading!

    On further notice I may have busted my speakers when accidentally combining the speaker positive wire and the ground wire? Not sure how all that works.
     
    Last edited: Apr 23, 2013
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Depending on your luck, you may have damaged any one or more of the following:

    1) the amplifier

    2) the transistor

    3) the speakers

    People come up with some weird and wonderful ways of connecting LEDs (or other lights) to the outputs of amplifiers, and yours is no exception...

    Well, maybe one exception. It's close to something that might even work.

    If you had placed a resistor in series with the base connection, everything except for the transistor would have been safe...

    One option you could try, and which might work, is to place the AC inputs of a bridge rectifier on the L and R outputs of your amplifier, and then to place the LED strip across the DC output of the rectifier. This assumes that the LED strip is designed to be connected to 12V and has current limiting resistors.

    Your poor sound could be due to damage to the amplifier or speakers, or because excessive current is flowing from one output to the other via the base-emitter junction of the transistor (which WILL fail at a moderate volume -- kinda like what you report)
     
  3. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    I drew this up while Steve was posting. The value of R1 is nominal. That said, Steve's bridge rectifier suggestion would work fine too.

    Chris
     

    Attached Files:

  4. cjohnb

    cjohnb

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    Apr 23, 2013
    @CDrive
    What is the resistor on the speaker in wire for?
    The "speaker in" wire would be the + front speaker terminal?
    And the positive speaker connects to the base lead?
    Wouldn't that force it to require louder sound output to cut the lights on?
    Does R1 330 mean a 330 ohms resistor? If so, why 330 ohms?
    What is D1? A Diode? And what ground source is it connected to? The radios ground or the cars ground?

    -Sorry for all the questions, I want to understand why it works not just know that it works.

    And the emitter connects to what?

    But even when I cut the lights off via a switch inbetween the battery and LEDS, it still makes that noise? Is that because it still crosses over at the transistor's BASE-EMITTER junction?

    To see if my speakers are busted or if they are just being messed with via the transistor, should I disconnect the transistor and see what effect it provides?
     
    Last edited: Apr 23, 2013
  5. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    You can't drive the base of a transistor without some form of current limiting. Not doing so will eventually pop the Base - Emitter junction. It could also damage the output amp. The emitter is connected to chassis ground as shown.

    Chris

    Yes, that's 330 Ohms. The Diode is used to protect the Base-Emitter junction during negative excursions of the audio waveform.
     
    Last edited: Apr 23, 2013
  6. cjohnb

    cjohnb

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    Apr 23, 2013
    So r1 330 is a resistor of 330 ohms?
    Also can the 1N4002 diode be replaced with a 1N4742A?(12V Zener Diode 21 mA Current AND Max Power Dissipation: 1.0W)?
     
    Last edited: Apr 23, 2013
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    No, it is the resistance.

    It is a 330 ohm resistor

    Like 12 volt battery, or 10 gallon hat, or 2 litres of orange juice, or a 4 door car. Ohms are the units which measure the main specification of a resistor.

    You wouldn't ask for a 4 door orange juice, a 12 volt hat.
     
  8. cjohnb

    cjohnb

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    Apr 23, 2013
    [[The Diode is used to protect the Base-Emitter junction during negative excursions of the audio waveform.]]

    Care to elaborate? Why would you want to run power from the GND wire to The Collector lead?

    + So I have taken the transistor outta my car and the idea of it distorting the car audio at moderate level volume was correct. Now I am going to try Chris circuit. In other words, my speakers are not busted.

    So is this technically the same as your diagram? I didn't understand the 3 grounds?
    [​IMG]
     
    Last edited: Apr 23, 2013
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The diode conducts, limiting the reverse voltage applied to the base. How it does so is unimportant, it just does.

    Glad that the sound is fine without the transistor attached. It was hopefully the weak point and (fingers crossed) your amp has not been damaged. The transistor may be damaged though.

    Yes the diagram is essentially the same. All grounds are connected together, and that is what you have done. Similarly, in another circuit the connection to the battery might be shown more than once. All of these would be connected together too. It's shorthand that eliminates some complexity in the drawing.

    Your drawing has the emitter identified correctly, but the connection labelled as "base" is actually the collector. The real base is the one connected to the speaker via a resistor.
     
  10. cjohnb

    cjohnb

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    Apr 23, 2013
    My bad lol I knew the speaker in was the base, I'm not sure why I had base right there. What does limiting the reverse voltage mean?
     
  11. cjohnb

    cjohnb

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    Apr 23, 2013
    I will try this out tomorrow morning and hope it works... Dangit, not sure if I have a 330 resistor... I will just find one in that range.
     
  12. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    When circuits become complex running wire traces all over the schematic to indicate ground makes no sense and just confuses things. If you're going to pursue electronics as a hobby get used to seeing the GND symbol drawn many times in schematics. They're all the same electrical (node) point. ;)

    Chris
     
  13. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    What values do you have? It's not a critical value

    Chris
     
  14. cjohnb

    cjohnb

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    Apr 23, 2013
    I went and bought a 1/2 watt 330 ohms resistor. The lights work fine, but again they don't work with the chasis gnd, just the corresponding speakers ground. Anyways, they no longer interfere with the speaker's sound quality. Just a question or two:
    1. Is the diode necessary? What would happen without it?
    2. If I double up the resistor would it be a 1 watt 660 ohm or 1/2 watt 330 ohms? And would it make the lights require a stronger signal for the transistor to cut on?

    The best news is that it doesn't make my speakers sound busted though. Thankyou very much Chris
     
  15. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    (1)I really don't see how the low side of your speakers could not be grounded. If they were floating above ground there would be no path to ground for your LED string. Todays autos have quite a bit of plastic in them. Are you sure you were connected to ground?

    (2) The Diode is absolutely necessary.

    (3) In your case doubling the value of the base resistor will do little. Why do you want to do this?

    Chris
     
  16. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    If you want the flash point adjustable you can to this. I'm assuming that your LED string is pulling under 100mA.

    Chris
     

    Attached Files:

  17. cjohnb

    cjohnb

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    Apr 23, 2013
    Why is the diode necessary?
    And yes, I am sure I was grounded. Touched it to the metal floor(which worked when just connecting leds from batter to that floor) and I also used the car's ground wire that connects to the radio. I am using an aftermarket radio not that it should affect anything.

    Ya a potentiometer(if that is correct) could work I suppose. Is there anyway it could be added before the leds? If it is added after, then I would have to add one to every speaker's leds.
     
  18. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    See here.
     
  19. cjohnb

    cjohnb

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    Apr 23, 2013
    Ya.... that doesn't answer my question. My question is:

    Why is it important, not is it important.
    I respect your mod status steve, but if your not going to properly answer the question, please don't respond.
     
  20. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    When we answer questions we first evaluate the perceived knowledge of the OP. When it appears that a detailed answer, that includes semiconductor theory and design, will only lead to more questions or not be understood anyway we reply like Steve did. We get all kinds of people that blow in and out of here. All with different levels of expertise. Some are students that desire detailed replies that delve into theory but some just want what Steve gave you.

    Tip: If (most likely when) a police officer pulls you over don't cop an attitude like you did with Steve. Not heeding this golden rule will only bring misery down on you. What would have been a simple traffic stop will turn into 2 hour ordeal while the officer looks for any and everything to the point of getting writers cramp! :rolleyes:

    Our mods are some of the friendliest and down to earth people you'll find anywhere on any forum. So if you like it here be nice.

    Chris
     
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