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1V audio burst every OTHER pushbutton

Discussion in 'Audio' started by devin, Jul 28, 2015.

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  1. devin

    devin

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    Jul 28, 2015
    Hello all!

    I am trying to build a circuit which emits a 1V high frequency audio signal (maybe 10kHz?) for about 5ms every OTHER time a pushbutton is depressed. Can a 555 be configured in this way? Or what is the simplest, most inexpensive way to accomplish this? I am a complete beginner here, but I have been tasked with a very specific project and would greatly appreciate some help!

    Thanks!!
     
  2. Laplace

    Laplace

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    Apr 4, 2010
    A functional diagram of this circuit would have the pushbutton switch (properly de-bounced) driving the clock input of a flip-flop, the Q output of the FF triggers a 555 monostable producing a 5ms pulse which gates a 10kHz signal being generated by a second 555.
     
  3. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    What is it about the 555 that continues to always tweak my interest and draw me to those threads? Take this thread for example. LL's reply involves debouncing the switch and a logic block (FF) chip. All logical stuff but as usual it gets me thinking "Can I do this exclusively with 555's"? My gut says yes. ;)

    Chris
     
  4. devin

    devin

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    Jul 28, 2015
    Hey guys! I've been learning a lot since I first posted (I have absolutely no background in this stuff!) and I have a slightly altered version of what I'm looking to accomplish:

    I need to build a circuit which emits a 5ms 10kHz sine-ified tone at an adjustable output voltage from 0-1.4V and has an adjustable delay from 0-100ms, triggered solely whenever a 9V battery input through a hall effect sensor drops from 9V (or any voltage?) to zero.

    What do y'all think??
     
  5. Laplace

    Laplace

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    Apr 4, 2010
    I think you should draw a functional block diagram for this circuit, and post it here. Indicate in particular which Hall effect sensor you have chosen to work with.
     
  6. devin

    devin

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    Jul 28, 2015
    Laplace, my difficulty is that I have zero clue about any of this stuff. I'm kinda hoping someone here would be willing to draw it up for me with a list of the parts I'd need, and then I might be able to go assemble it with some help from a friend... would you mind scribbling out a functional block diagram that you think would work? Actually, I'm thinking now that the device could be powered by +48V "Phantom Power" coming off a sound mixer board?
     
  7. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    I think I'll put you on the clock and bill you. ....Just kidding! :p

    Do as Laplace suggested.

    Chris
     
  8. devin

    devin

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    Jul 28, 2015
    Chris, lol I'd actually be willing to pay some small amount for this, but some friends told me this should be so simple for smart people like you to whip out that I should just go online and ask someone to do a quick drawing of what I'd need... I have no clue what I'm doing or even where to start with drawing a diagram
     
  9. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    You know,.. I was just kidding when I made my last post but now you're bordering on being a candidate for our "Nubies Mystery Circuit Circus". This is a section of our forum that was suggested by one of our Moderators. I think it was Steve but I'm not positive.

    If you don't want to be classified as a candidate for it I think it would behoove you to keep no secrets and fully divulge exactly what you're desirous of building ...at the starting gate.

    One more tip: If you continually change your project requirements you will be put in the N.M.C.C section by default. ...Nobody goes there to read posts! :rolleyes:

    Chris
     
  10. devin

    devin

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    Jul 28, 2015
    Have I mentioned that it needs to brew my coffee too?

    This device will be fastened to the sustain pedal mechanics of an acoustic grand piano. As the pipe for the pedal moves up and down as the pedal is played, I need the device to send out a short 10kHz sine wave burst when the pedal is almost finished with its release after being depressed. To do this, a hall effect sensor will be positioned close to the moving pipe which will have two magnets on it: the nominal position magnet opening the circuit and the depression position magnet closing it; going from closed to open is what triggers the 5ms burst. This 10kHz burst will be summed through a "Y" cable with the signal from a dynamic microphone designed to pick up the low frequencies of the piano. (This signal will be intermixed later with a stereo pair of typical piano mics on the mids and highs). The problem on the release is that all 88 dampers come slamming down on the strings to mute them, and a considerable thump is picked up by the mic. My plan is to use the 10kHz burst to trigger a short compression of the mic signal on the mixer board. This would be done by assuring that the 10kHz burst is at least 30dB louder than the max mic signal of the piano, and placing the compressor threshold somewhere in between the two. Then, a low-pass filter at 100Hz will be applied to the signal after the compressor to hide the 10kHz burst. It would be nice to have this device run on Phantom Power (which the mic ignores) and be able to adjust the output volume of the burst from 0-1.4V (future proofing it for line level signals) and to have a delay of 0-100s (to time align it exactly with the thump). The burst must be clean, with no artifacts or subharmonics of its own.

    Does this help to clarify things?
     
    Last edited: Jul 29, 2015
  11. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Yes it does. It included details that will go a long way in aiding us to help you. ;) It also keeps you safe from falling into the dreaded Nubies Mystery Circuit Circus section. :p

    Chris
     
  12. devin

    devin

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    Jul 28, 2015
    Darn, that almost sounded like a fun place.
     
  13. devin

    devin

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    Jul 28, 2015
    I should clarify that I meant to type a delay of 0-100ms, not seconds. Also, I believe I mean 1.4V RMS power, not peak. And for added disclosure, I am a mere sound engineer and musician trying to get creative with mic techniques, and have next to zero experience with electronics! I'll need a lot of spoonfeeding...
     
    Last edited: Jul 30, 2015
  14. devin

    devin

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    Jul 28, 2015
    What do you think of this? Someone drew this up for me, and I have zero clue what anything means... is this what you'd recommend? Would you make any alterations?
     

    Attached Files:

  15. Laplace

    Laplace

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    Apr 4, 2010
    It seems as though two magnets would not be necessary - just sensing the down position of the pipe should be sufficient, i.e. if the pipe is not down then the pedal has been depressed and the pipe is up. Unless the idea is to sense how much the pedal has been depressed so the wave burst is provided only when the damper drops from its maximum height above the strings, but not otherwise when the damper drops more softly from a lesser height.

    So what is the desired operation? Trigger operation on every fall of the damper, or trigger operation only on the condition that the pedal has been fully depressed?
     
  16. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
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    May 8, 2012
    Ask him what chip he's using there. It's not indicated on the print. At a glance I can see he's knowledgeable.

    Chris
     
  17. Laplace

    Laplace

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    Apr 4, 2010
    The only chip that makes sense is the CD4093B Schmitt trigger. Unlike the 555 the trigger voltage points may fall anywhere in a wide range, but they tend not to drift much. So the adjustment for the RC time constants need to accommodate this range, but once set they should remain stable for changes in operating temperature.

    It also seems clear that the Hall sensor works with a single magnet setup.

    Is the "Phantom Power" mentioned above equal to the 48 VDC shown in the circuit diagram?
     
    Last edited: Jul 30, 2015
  18. devin

    devin

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    Jul 28, 2015
    yes it was the 4093, and yes phantom power is 48V. I don't understand how the hall effect sensor works, so if one magnet will do, then great! I'd just place the magnet on the pedal so that it is triggering the sensor during the depressed position?
     
  19. devin

    devin

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    Jul 28, 2015
    ok new set of questions about this. some people i've been talking to are concerned that the circuit output will be greatly affected by the impedance of the mic that I will be "Y" cabling it with. and also, there is some concern that sending this 10kHz burst down the mic line will overload the mic itself. I can maybe fix this problem by using something other than a mic... I can use a piano "pickup" which works like an electric guitar pickup (no moving parts, no acoustic mechanism, works purely on magnetic field sensing the metal piano string vibrating nearby). I have a simple electrical meter, is there a way I can measure the impedance of this pickup to know how it might affect the circuit? (I feel like i'm trying to speak Chinese here).

    Laplace, my ignorance must be stunting my creativity here, because I did not even think something like the exact position or speed of the pedal movement could be accounted for! Are you saying that there might be a way to have the sensor detect this? Because, the thing that really causes the thump is the speed at which the pedal is released, whether the depression/release was only partial or the full thing. The dampers hitting the strings fast and hard is the problem. Is there a way to only trigger the circuit when the pedal is moving above a certain speed near the end of the release? I don't know what all is possible here...
     
  20. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    648
    May 8, 2012
    Using a 'Y' connection to parallel the Mic isn't a good idea. I think you would be well advised to use mixer techniques.

    Chris
     
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