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  1. audioguru2

    500W_inveter

    Hi Ren, The pre-driver, driver and output transistors in the 500W inverter project are designed to switch fully-on then fully off so they don't get too hot. If you make a 500W sine-wave inverter with any kind of sine-wave oscillator feeding a 500W audio power amplifier that drives a big step-up...
  2. audioguru2

    voltage regulators

    Horray! Kevin's back. ;D Hi Kevin. A series pass regulator sources a voltage to a load. The load sinks current to ground. A shunt regulator like a zener diode sinks excess current to ground all the time from a series source resistor and the shunt regulator is parallel to the load. Maybe you...
  3. audioguru2

    Resistance wattage in series

    Maybe it is needed to discharge the 10uF cap quickly when the power is cutoff. Two 240 ohm - 1/2W resistors in series is equal to a 480 ohm - 1W resistor. Maybe the designer had lots of 240 ohm - 1/2W resistors. Maybe he needs 480 ohms but only 470 ohms is available. No, LEDs don't limit...
  4. audioguru2

    designing a power audio amplifier with OP AMP

    Hi Shaiq, The current requirement for the LM380 amplifier is calculated with simple arithmatic using the power graph in the datasheet. The continuous max current is so low at 245mA that a better-quality 500mA transformer should be used. The voltage from a little 300mA transformer varies all over...
  5. audioguru2

    How to make a remote control fart machine

    You'll know when you are fully charged when you gotta blow! ;D
  6. audioguru2

    current series feed back in amplfiers

    Current feedback. Voltage feedback. Series feedback. Parallel feedback. Confusing words. Why not just call the feedback that is caused by the emitter resistor, emitter resistor feedback? Then call the feedback caused by a resistor from the collector to the base, collector to base feedback? 
  7. audioguru2

    Input signal for LM3915. need help.

    All circuits that I showed have a "volume control" to set the circuit's sensitivity. Yes, but you adjust the sensitivity of your circuit to match the accurate reading of their sound level meter when a sound is playing, and your mic is the same distance and location from the sound source as...
  8. audioguru2

    Urgent help

    The OPA445AP is made by the Burr-Brown division of Texas Instruments and is available worldwide at Farnell and many other distribution companies. It is the only opamp I know that has a high supply voltage rating.
  9. audioguru2

    difference between negative supply and ground???

    Hi Jspn, I've already said it. Ordinary opamps don't work if their inputs or output voltage is near their negative supply voltage. So you connect a negative voltage to the negative supply pin then they can operate fine with their inputs and output voltages at ground. If you connected their...
  10. audioguru2

    difference between negative supply and ground???

    Hi Shaiq, Many circuits must operate with their input or output at ground. But ordinary opamps don't work with their inputs or output at their negative supply voltage, so they use a negative supply to allow their inputs and output to work at ground. The ground is where the positive supply and...
  11. audioguru2

    designing a power audio amplifier with OP AMP

    Yes, I've included it. The LM380 has enough gain for a CD or MP3 player to be switched to the volume control and to disconnect the mic preamp. I have put the two together for you with everything I can think about to make a nice little amplifier.
  12. audioguru2

    Audio Amplifier Plz check this out

    Hi Shaiq, Even the tutorial has the circuit for the LM380 messed-up: 1) It spec's a non-polar cap for the input when the mic is positive and the input of the LM380 is internally DC grounded. 2) The value of the input cap is huge. Its low frequency response begins dropping at 16Hz. Half-power is...
  13. audioguru2

    Audio Amplifier Plz check this out

    Hi Shaiq, No, your circuit won't work with an LM380 as its power amp. :'( You have its pin 2 connected to the feedback for the TL071, so its voltage is not at ground like it is supposed to be. It is also probably messing-up the TL071. R7 and C5 don't do anything and should be removed. The value...
  14. audioguru2

    designing a power audio amplifier with OP AMP

    The LM380 isn't an opamp. It is an audio power amp with built-in biasing and negative feedback. It is a power amplifier. With a 12V supply it provides 1W at clipping to an 8 ohm speaker. I use the LM390 power amp (obsolete now) which is similar but has higher output power (2W) because it...
  15. audioguru2

    Audio Amplifier Plz check this out

    Hi Shaiq, I had to adjust the contrast on your schematic so I could see it. I also transferred it to a much smaller PNG file. Your mic preamp looks nice. The value of its R3 seems to be too high. The old LM312H was an opamp, not a power amp, that hasn't been made for 10 years. You don't have...
  16. audioguru2

    Input signal for LM3915. need help.

    Your circuit with the LM3915 will be a sound level meter after it's mic sensitivity and circuit's gain is calibrated with a real one. The LM3915 is just a voltmeter with a logarithmic scale. Go to a sound system installation company and set yours to read the same as theirs. RadioShack also has...
  17. audioguru2

    Switching idea

    I was driving along on a hot summer day and saw a huge farmer's field full of snow. Snow on a hot day in summer?? I got closer and saw millions of white turkeys. So many that they were holding each other up. I got a nice big one and froze it for Christmas. I've inverted the comparator for you...
  18. audioguru2

    Keys Finder

    Nobody has talked about this project for a while: http://www.electronics-lab.com/projects/misc/002/index.html It has very high gain when the piezo sounder is used as a microphone and only a little filtering. I wonder how well it works. Recently my daughter brought me a Keys Finder that she got...
  19. audioguru2

    500W_inveter

  20. audioguru2

    motion detector, N.C COM

    The Vdd of a ToothPIC is +5V. Input voltages must not exceed +5.5V. You can power its built-in 5V voltage regulator with +12V if you want. 1) Connect the COM of the detector to the ToothPic's Vss (ground). 2) On the ToothPIC, connect a 10k pull-up resistor from Vdd (5V) to the input to provide...
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