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  1. Audioguru

    Amplify signal from piezoeletric

    The fullwave rectifier circuit I posted should be fed from a low resistance to ground signal source like from a preamp opamp powered from a dual polarity supply. If an LM358 opamp is used for the fullwave rectifier and its input is capacitor-coupled from the output if the preamp then the input...
  2. Audioguru

    help please

    Use speaker wires. For my stereo I use 18 gauge lamp cord pair of wires. Connect the tweeter to one channel output of the stereo amplifier. Connect the tone generator to the channel's input.
  3. Audioguru

    Simple LED circuit burning out

    The huge LED in the article has a maximum allowed current of 80mA. Your "super bright" LED has a datasheet that states its maximum allowed current that might be only 30mA. Most ordinary LEDs are spec'd at 20mA. Of course it will burn out if it has a current of 80mA. 20mA will not cause the LED...
  4. Audioguru

    Simple LED circuit burning out

    Simple arithmetic: 1) The huge LED has a maximum allowed current of 80mA but 70mA is recommended. 2) Its minimum forward voltage is 3.0V. 3) The 82 ohm resistor might be a little low at 78 ohms. 4) The current is (9V - 3V)/78 ohms= 77mA. It should survive but the wood is blocking its cooling...
  5. Audioguru

    help please

    I have never heard about or seen the levitation of small lightweight polystyrene balls using ultrasonic power. I think your expensive tweeter will soon burn out, probably before levitation occurs.
  6. Audioguru

    Amplify signal from piezoeletric

    Tr
  7. Audioguru

    tip120 driving led array

    An LED part number has a range of forward voltage. Each LED will probably have a different voltage. You have LEDs connected directly in parallel so the one with the lowest forward voltage will hog most of the current and soon burn out. To prevent the burn out you must measure each LED and match...
  8. Audioguru

    help please

    An audio tweeter is very fragile. It is designed to play the brief occasional very high frequencies in music or speech. Continuous power will destroy it. It might survive only a few Watts of power continuously. Why use a tweeter? It is fed AC from the amplifier but a levitator uses DC with no...
  9. Audioguru

    Amplify signal from piezoeletric

    Yes, try 1M as R1 in the preamp circuit. Your preamp uses a single supply but your rectifier needs a dual polarity supply. Why don't you use a single opamp with a single supply for the fullwave rectifier? I use an MC33171 opamp that is a single opamp similar but better than an opamp in an LM324...
  10. Audioguru

    Amplify signal from piezoeletric

    The bias current for the PO07 opamp is very low so you could try a 1M bias resistor to see if the low frequencies from the piezo are better. I have never tested that fullwave rectifier circuit.
  11. Audioguru

    Amplify signal from piezoeletric

    Which opamp part number and what is its supply voltage? You did not attach a schematic of a full-wave rectifier circuit.
  12. Audioguru

    Amplify signal from piezoeletric

    A piezo transducer has such a horrible frequency response that I have never used one as a speaker or microphone. Since your opamp has no part number then we do not know if it has a very high input impedance and low input current so the 100k bias resistor can be increased to 1M or higher. Then...
  13. Audioguru

    Amplify signal from piezoeletric

    You do not show the value of R1. If it is 330 ohms then 48Hz is reduced by by -3dB and 4.8Hz is way down by -20dB. A piezo is very sensitive to its high frequency resonances. It produces a strong low frequency signal when it is tapped with your finger. Tap it every time you cough.
  14. Audioguru

    Amplify signal from piezoeletric

    "During an actual sample, the input resistance is temporarily a lot lower" then you explained why.
  15. Audioguru

    LED id

    An LED also has a certain "viewing angle". A narrow angle makes a small bright spot directly in front of it and a wide angle shines its light all around but looks not as bright. The Shack is bankrupt partially because they knew nothing about electronics. They listed only the size and weight of...
  16. Audioguru

    How to Figure out What Power Supply to Use (Battery Conversion)

    I have a couple of wall-warts that are 12VDC at 1A and they are pretty big. If the current is higher than 1A then the size and weight will be too big for a wall-wart, its weight might keep unplugging it. A switched-mode wall-wart is very small and lightweight and if you find one it can easily be...
  17. Audioguru

    Board design help! Some buttons and led on a perfboard

    Perf boards from Radio Shack were also very poor quality and their holes were too big.
  18. Audioguru

    Board design help! Some buttons and led on a perfboard

    When my local supplier ran out of real UK-made Veroboard, I bought some stripboards that were made in China. Its base was not blue epoxy-fiberglass, instead it looked like and smelled like animal dung and was warped. The chewing gum they used to glue on the "copper?" strips did not do a good...
  19. Audioguru

    Voltage Regulator Build

    The 60VAC input will cause a circuit to be complicated to reduce the severe heating. Use a transformer to convert the 60VAC to 12VAC then it is simple. A 120V to 24V transformer will be fine.
  20. Audioguru

    Diy multi bank battery charger

    You need a battery charger circuit that is designed to charge old lead-acid batteries. I have never used a lead-acid battery except the one in my car.
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