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  1. audioguru2

    "Power?" Inverter

    Jonathan, Even better, replace your 555 and gate drivers with a 4047 oscillator/divider/direct-and-inverted-outputs chip that directly drives the gates. Its digitally-divided outputs are exactly 50-50 symmetrical. An output of 300W from one pair of MOSFETs would be easy.
  2. audioguru2

    hv polarity indicator/ voltage optimizer

    Kevin, A TV's Cathode Ray Tube (CRT) operates like a normal vacuum tube, except its "plate" is the screen (covered with phosphors). The screen is connected to the very high voltage which accellerates the electrons emitted by the heated cathode, which is near ground. The grid of the CRT (and...
  3. audioguru2

    Capacitors and energy

    Kevin, Current is a FLOW of electrons. When a capacitor is charged, the current flow stops. The capacitor stores energy, which is its charged voltage and the potential, or ability, to deliver a current during discharge.
  4. audioguru2

    Electronic Stethoscope

    MP, Never mind the special LM387 "phonograph preamp", how about using a standard, available and low noise opamp? How do we get the project corrected?
  5. audioguru2

    Electronic Stethoscope

    MP, Digikey won't sell me an LM387 (quantity available = 0) and neither will Newark Inone. Why would anyone want to use it now, without any manufacturer second-sourcing it and with its non-standard pin-out? There is nothing special about it in this circuit, a standard low-noise opamp is fine...
  6. audioguru2

    Stereo volume control from TI

    Kasamiko, It can be controlled by a micro-controller chip.
  7. audioguru2

    Weird relay problem..

    Kasamiko, Please post a schematic of your monostable, maybe it is re-triggering (cutting power) when it should be driving the relay continuously. If you power the coil of the relay from a battery as a test then the relay contacts will be proven.
  8. audioguru2

    Repairing Home Amp

    Mmphoneman, You are lucky that it has 2 channels and 1 that still works. Remove the fuses and power and measure for a much lower resistance on the bad channel, probably at the output transistors or power ICs. By comparing measurements of the good channel to the bad one, then you'll find the problem.
  9. audioguru2

    Selectable source?

    Stuee, Weren't you enquiring about digital pots for your car on the other post? The chip that you need is custom-manufactured for car audio systems, with scanning function-selectors, and either has audio digital pots and display circuitry built-in or it interfaces with those custom chips...
  10. audioguru2

    Electronic Stethoscope

    Alhilaly, As you can see the many replies about this project, the schematic and parts list have errors. Until the errors are corrected it is awkward to give you a detailed circuit description.
  11. audioguru2

    8 SOIC to DIP adapter

    Mixos, That's a nice one. Also try rotating the SOIC by 90 degrees so that it can be an 8-pin DIP without any extra pin spacing.
  12. audioguru2

    Weird relay problem..

    Kasamiko, Doesn't your voltage monitoring prove that the relay is OK? Maybe the mains voltage is low before or after a power failure which causes a "freon" bubble with a delay.
  13. audioguru2

    My 120 Watts Power Inverter

    Kasamiko, With 11V across the 47 ohm resistors, half the time, the power dissipated is only about 1.25W. Maybe they are small and normally reach a very, very high temperature at their maximum rating (5W) so therefore get hot at 1/4 of their rating. Try physically larger or higher power rating...
  14. audioguru2

    Weird relay problem..

    Kasamiko, 1) Maybe something is happening to the "freon" during the delay. The motor works hard, but normally, without a delay. But it runs smooth and quiet (and doesn't do its job) after the delay. Perhaps the "freon" developes a gas bubble because it warms-up during the delay, at a location...
  15. audioguru2

    Generators

    MP, I was refering to Steven charging his capacitors with DC, just like recharging a battery. When you charge a capacitor, DC current flows into it. A charged capacitor has the current that has flowed into it "on-hold", waiting to be released (during discharge). Ante, I agree that a capacitor...
  16. audioguru2

    sensitive low frequency filter

    Electrodoc, A very simple 200Hz low-pass filter can be added to the Velleman kit: 1) Add a 3.3nF capacitor across RV1. 2) Add an 18nF capacitor across R13. The LEDs will flash to the bass and beat of the music.
  17. audioguru2

    Capacitor charging

    Kevin, Connect a resistor in series with a capacitor, so that the resistor can charge and discharge the capacitor. Connect a signal to the resistor. You now have a linear low-pass filter, with its output across the capacitor. It doesn't matter that the capacitor charging is exponential instead...
  18. audioguru2

    Generators

    MP, Yes, a capacitor stores current, like a rechargeable battery. It also releases its stored current during discharge. The value of the capacitor determines how much current can be stored or released, per time. You might say that a capacitor stores electrons or holes, but I like to think of it...
  19. audioguru2

    touch switch

    Thanks, MP. Are you able to attach the schematic to the project? Maybe you could add a note about why the author neglected to tie-down (ground) the floating inputs of the unused gates. PS Maybe a warning not to use the circuit in winter if the humidity is low which causes a lot of static...
  20. audioguru2

    Generators

    Steven, Try feeding the generator to a step-up transformer, then rectify its output. When you parallel capacitors, the voltage rating remains the same, not doubled. But the current storage is doubled. If you put two equal-value capacitors in series, the voltage rating is doubled, but the current...
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