Plasma ball audio sensitivity adjustment?

Discussion in 'The Projects Forum' started by darticus, Oct 18, 2012.

  1. darticus

    Thread Starter New Member

    Oct 18, 2012
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    Spencer Gifts ball has an audio setting but if the sound isn't very very loud it won't light. What can be done? Not a bad ball but audio setting terrible. You probably have to put it on a speaker to get it to work properly. Ron
     
  2. DickCappels

    Moderator

    Aug 21, 2008
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    Buy some earplugs.
    Or more seriously, most likely, the part you are interested in is a monolithic circuit stuck to a circuit board with a blob of epoxy. If that is the case, there is little you can do except possibly see if a different microphone helps.

    More of a long shot: If some of the circuitry is exposed, tell us about it, or even better post a circuit diagram and maybe somebody can recommend circuit changes.
     
  3. darticus

    Thread Starter New Member

    Oct 18, 2012
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    Took the Spencer gift globe apart. Looks like we have a small mic in there picking up sound above 2 sections of plastic on the inside of the base. Any thoughts on making the sensitivity better? Did any one try to move the mic to the outside??? Thanks Ron

     
    Last edited: Oct 19, 2012
  4. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Ok, what you're going to need to look at are probably the resistors going to that chip. Could you tell us what the numbers are on the chip? Once we figure that out, it shouldn't be too hard to mod the design.
     
  5. darticus

    Thread Starter New Member

    Oct 18, 2012
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    Took the mic out and now when a loud sound is heard it stays on and doesn't shut off. The sound also has to be loud to turn it on. Checking this out a bit before opening it up again. Will get back. I did add 8 inch wires to get the mic to the outside plus extra wire. I thought it would just get more sensitive. It doesn't seem more sensitive but once it comes on it stays lit before I took the mic out it would shut off after lighting. Maybe I'll try to just reverse the mic wires. Could it be the 8 inch wires??? Seems like you can get a slight shock from the mic body outside. Thanks Ron

     
    Last edited: Oct 19, 2012
  6. Audioguru

    New Member

    Dec 20, 2007
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    A microphone has a very low output level then its preamp has high gain.
    If you use ordinary wires to connect the mic to the preamp then the wires are antennas that pickup mains hum and other interference.
    You should use shielded audio cable to connect the mic to the preamp.
     
  7. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    That's weird. I posted here, but now it's disappeared....

    Anyway, what I said was pretty much what AG mentioned. The mic is picking up interference (stray electricity) from the globe and it's constantly triggering the audio circuitry. You can see the electric charge if you place a coin on top of the globe and touch it with another coin. You'll see the spark.

    I would not have removed the mic, personally. I have a feeling the chip is acting as the audio amplifier, and at least one of the resistors going to it adjusts the sensitivity. Knowing what the numbers on the chip are would help a lot.
     
  8. darticus

    Thread Starter New Member

    Oct 18, 2012
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    Switched the wires on the mic to see what would happen but after doing so the mic didn't work so I put it back again. Should I try to use some shielded mic wire? The chip says HEF4069UBP, L2A4D2 21,
    UNG12125, NXP. Does this help anything? Should I try the shielded wire or just put the mic back in. SEE PIC. Thanks Ron

     
  9. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    Hmm, I wonder why there's a hex inverter in a plasma globe. I suppose they could be using it as an audio amplifier...
     
  10. Audioguru

    New Member

    Dec 20, 2007
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    Yes, a Cmos inverter can have a voltage gain of about 200 up to 200Hz with a 3V supply.
    With a 5V supply the voltage gain is 100 up to 200kHz.
    With a 10V supply the voltage gain is about 40 up to about 2MHz.

    The output is fairly distorted but to trigger the light the distortion does not matter.
    The circuit biases itself.
     
  11. Audioguru

    New Member

    Dec 20, 2007
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    Switching the wires connects the microphone backwards so of course it doesn't work.
    See my last post where I said to use shielded audio cable (mic wire). The shield should be the ground wire.
     
  12. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    So I guess the question remains--how is this particular circuit set up, and which resistors would need to be changed to adjust sensitivity?

    I don't suppose you know how to create a schematic by looking at a PCB, do you darticus?
     
  13. darticus

    Thread Starter New Member

    Oct 18, 2012
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    APPRECIATE all the suggestions. I couldn't follow what most were saying so I put it back to factory with mic inside. I built a color organ kit to plugged the ball into it but after 1 hour the transformer for the plasma ball burnt up and stopped working. It was working great before this but with not as much viewable spark activity. Any thoughts on how to solve the transformer problem? Its 12vdc 830mA. Trying it now with a 12vdc 500mA and its working without plugging into the color organ controller which I'm sure will burn the transformer out faster.
     
  14. DerStrom8

    Well-Known Member

    Feb 20, 2011
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    You'll need a larger transformer (i.e. 12vdc, 2 amp) to be sure you can source enough current to power the plasma globe and the color organ. My guess is you were trying to draw too much from the transformer and the inner windings got too hot and burnt.
     
  15. darticus

    Thread Starter New Member

    Oct 18, 2012
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    The color organ was using its own 120vac power and the plasma ball using its 12vdc 830mA transformer. Thanks Ron
     
  16. Alian

    New Member

    Oct 21, 2012
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    Thankyou very much
     
  17. darticus

    Thread Starter New Member

    Oct 18, 2012
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    You are very welcome!
     
  18. darticus

    Thread Starter New Member

    Oct 18, 2012
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    I think the transformer for the plasma ball couldn't take the on off repeatedly. The color organ was using its own power, so that was not the problem. I did notice that the plasma ball was only getting about 50-60% of the voltage needed to run the plasma ball as the factory made it. The transformer probably only got (8vdc) a portion of the power needed to run the plasma ball correctly due to the color organs circuitry only putting out 50-60% of the in voltage which was 12vdc 830mA 100% and caused the transformer to burn out. I did get a new 830mA transformer. With this info can anyone advise of the fix for the problem of the transformer burning out. Thanks Ron
     
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