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  1. L

    1V audio burst every OTHER pushbutton

    From your questions I would surmise that you have decided not to employ optical slits with a plunger for light cutoff to the sensor. Since I have no familiarity with pianos of any kind or their damper mechanisms, it is difficult to imagine what can be achieved otherwise. Does the damper...
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    1V audio burst every OTHER pushbutton

    False triggering by stage lighting - Depends on how you build the sensor. I imagined mounting the LED & photo-transistor on opposite sides of a 1/4" brass tube and cutting the optical slit with a razor saw. A polished stainless steel rod would fit inside the brass tube as the plunger attached...
  3. L

    1V audio burst every OTHER pushbutton

    What I'm thinking of for a velocity sensor would be two photo-transistors illuminated by two LEDs, spaced about 3/16" apart vertically. A shade attached to the lift pipe will descend and block the light for one and then both photo-transistors. The bottom photo-transistor will be aligned with...
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    1V audio burst every OTHER pushbutton

    What if you fed the mic signal into a pre-amp, then to a passive mixer to add the 10kHz burst (adjusting the pre-amp gain to offset the mixer loss), then to the compressor and low-pass filter? Seems like it would be a simple task to design the passive mixer as part of the burst device, maybe...
  5. L

    1V audio burst every OTHER pushbutton

    "...the 10kHz burst is at least 30dB louder than the max mic signal of the piano..." (from post #10)
  6. L

    1V audio burst every OTHER pushbutton

    Such a thing is possible. It would require two lift sensors (probably precision optical) near the bottom of the drop stroke. But then the question is, since the overdrive pulse is supposed to be audibly imperceptible, then what difference would it make?
  7. L

    1V audio burst every OTHER pushbutton

    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...
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    Help With Kids Homework

    I would agree with these two answers: Closing the switch so the power will go through the circuit The other is moving the circuit closer to the wire loop What the teacher wants is for you to recognize what will induce a current to flow in the wire loop. In the general case, current in the...
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    1V audio burst every OTHER pushbutton

    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...
  10. L

    1V audio burst every OTHER pushbutton

    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.
  11. L

    1V audio burst every OTHER pushbutton

    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.
  12. L

    capacitor plate voltages

    It is true that the voltage across the capacitor cannot change instantaneously. If the circuit forces one side of a capacitor to switch to a new voltage level then the same change in voltage will be reflected on the other side of the capacitor as well. It will depend on the circuit what...
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    Help With Kids Homework

    In the general case there are only three actions that will induce a voltage in the wire loop. A. Increasing the magnitude of the current flowing in the circuit 'coil'. B. Decreasing the magnitude of the current flowing in the circuit 'coil'. C. Moving the circuit coil so static field lines...
  14. L

    capacitor plate voltages

    It is the nature of a capacitor to maintain a constant voltage between its plates. The only way to change the voltage between the capacitor plates is to force a current to flow through the capacitor. But when we say that current flows through a capacitor we do not mean that charge moves...
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    (Help) Reducing MMC capacitance for Tesla Coil

    Distributing 10,000 volts equally requires a string of 25 equal-valued capacitors so that 400 volts will charge each capacitor. But with using the 0.22 µF capacitors, the total capacitance of the string will be only 0.0088 µF. To achieve a total capacitance of 0.02 µF requires three strings...
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    Help with Near field communication technology

    Did you find that circuit diagram floating in the aether, or did it have additional information attached?
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    Help with Near field communication technology

    Have you checked out resources such as: http://www.nearfieldcommunication.org/ http://apcmag.com/inside-nfc-how-near-field-communication-works.htm/ NFC is like having RFID in your cell phone or credit card. The electronics are analog but the modulation is digital because the data is digital...
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    Need to get a 2 wire input to be a 1 wire output.

    How did you expect negative to flow with only a positive power source as shown in the schematic? Does 'neutral' mean floating or grounded? If floating, then Wire-1 and Wire-2 could each activate a SPST relay that then connects its respective wire to Wire-3. Otherwise a more complicated...
  19. L

    Solve current when only power and resistance is given

    FYI, these are the two power equations I fed into Maple symbolic algebra engine to solve for the two node voltages:
  20. L

    Solve current when only power and resistance is given

    I put together the following spreadsheet to check the correctness of the two solutions. Recommend you do the same.
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