12v Frequency dependent switch?

Discussion in 'The Projects Forum' started by orange source, Dec 19, 2008.

  1. orange source

    Thread Starter New Member

    Dec 19, 2008
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    Firstly a big hello to everyone as this is my first post.

    I'm fairly new to this although I have built a fair few kits and can re-wire a 20k sound system in the dark but thought I'd try something a bit more adventurous but can't find any plans or circuits.

    I need something sound activated that will only activate at frequencies below say 100Hz one that activates between 500Hz 3KHz and one that activates at 5KHz and above.

    Also it has to run on 12v and output 12v to drive some EL wire or a bank of LEDs.

    Thanks for any help in advance
     
  2. bertus

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    Apr 5, 2008
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  3. orange source

    Thread Starter New Member

    Dec 19, 2008
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    Wow thanks bertus, will this run ok on 12v without frying?
    also would i be right in thinking i need to omit a few resistors to allow 12v output?

    and as a gesture of good will to all men I have about 10000 two colour (oblong) leds (orange and green) if any one wants some for the price of postage I'll send a bag of 100.
     
  4. eblc1388

    Senior Member

    Nov 28, 2008
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    The circuit bertus suggested in the previous post will work on 12V without any changes.

    I have checked the frequency ranges of the three channels and they are in about the same frequency range as what you have wanted.

    Now you need to decide on how many LEDs each channel will drive. Base on this new piece of information, the output driver part of the circuit can be finalized.
     
  5. orange source

    Thread Starter New Member

    Dec 19, 2008
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    it basically needs 12v 300 milliamp as its going to drive some EL wire Inverters.
     
  6. eblc1388

    Senior Member

    Nov 28, 2008
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    I don't think the outputs of that unit (which is intended for LEDs) can successfully drive an EL wire inverter because the ON time is very short. An inverter will take considerable time to generate a high voltage at its output and I don't think it will work with such a short power pulse.

    An alternate method is to have a single EL inverter fully powered ON, and use the outputs of this circuit to control the distribution of power to individual EL wire.

    The electrical switching involved not as simple as it seems because of the high voltage and frequency involved. See the following quote from WiKi.

    Maybe other members have some insight into this problem.

     
  7. orange source

    Thread Starter New Member

    Dec 19, 2008
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    The on time shouldn't be a problem, I have hooked ten lengths up to a maplin 10 channel chaser and that works fine even at the fastest speeds
     
  8. bertus

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    Apr 5, 2008
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    Hello,

    Here is an idea for an extention of the led organ.
    It is a comparator that can drive the EL inverters.

    [​IMG]

    At the moment when the leds get dim the inverter is switched on.
    When you want the inverter switched on when the leds go brighter, exchange the + and - inputs of the opamp.

    Greetings,
    Bertus
     
    Last edited: Dec 21, 2008
  9. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    They works because the supply is there all the time and the unit just distribute the power to its various output.

    You are facing a different situation here. When you pulse a switchmode power supply unit with a short electrical pulse, there is no way you can tell if it will produce the required output or not because it need time to stabilize.

    OK. I have designed a circuit that will have the music signal triggers a monostable so that the "short pulse to inverter supply" problem can be tackled.

    Note: The circuit below can only provide a max. of 200mA at the 555 output. For load that takes 300mA, an additional NPN drive transistor is needed.

    [​IMG]

    The monostable formed by the LM555 will trigger(you can adjust the trigger level via the input VR of the original unit) and hold the EL supply steady for a time between 0.1 ~ 1 second. This will enable the inverter to power up properly.
     
    Last edited: Dec 23, 2008
  10. bertus

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    Hello,

    I think the 555 solution will not work this way.
    The 555 is capable to drive 100 mA.
    So the 555 can not drive the 300 mA inverter, it still needs a driver transistor or mosfet.

    Greetings,
    Bertus
     
  11. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    You're right. Must have read some wrong data somewhere. Actually the max. drive from a 555 is 200mA.

    A NPN drive buffer will be needed in the above circuit.
     
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