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  1. audioguru2

    Electronic Stethoscope

    Prateek, Speakers? Are you using speakers instead of earphones? Maybe the microphone could hear the speakers and the circuit produced acousical feedback. When low-pass-filtered, it would make a humming noise in the speakers with an amplitude-modulated waveform.
  2. audioguru2

    Generating square wave of voltage levels 0-5V

    Kevin, If the collector of the PNP is swinging the full 4.9V peak-to-peak, then the voltage divider action of R4 and R5 will reduce that to only 158mV at the source of the FET. This reduction of Vgs (which is negative feedback) is negligible when compared to the 10V input swing. So Vgs will...
  3. audioguru2

    Generating square wave of voltage levels 0-5V

    Hi KM, The 2N5484 has a broad range of gate-source cutoff voltage, from -0.3V to -3.0V. Maybe your simulator averages this voltage to -1.6V. Since D2 limits the gate voltage to about -0.7V, then the 2N5484 never cuts-off, and the output at point "A" never gets close to ground. The 2n5484...
  4. audioguru2

    Electronic Stethoscope

    Hi Prateek, Welcome to our forum. I am sorry that you are having trouble with this project. Have you tried any of the corrections that I have recommended in this thread?
  5. audioguru2

    Boosting Regulator Current/ATX power supply

    Ante, MP, Thanks guys, ALT + Print-Screen works fine and I can paste it into Paint. Upgrade? Not yet. The computer is only a tool, and you guys help me a lot with it, thanks again. You should see my trusty (not rusty) single-channel, vacuum-tube (except my CMOS timebase, sync and transistorized...
  6. audioguru2

    Boosting Regulator Current/ATX power supply

    Yeah, My Print Screen button doesn't do anything in Win98 1st Ed. My whole computer is just an introductory sample of the real thing!
  7. audioguru2

    Audio Amplifier from Scratch

    Hi Quantum, That's great! Your amplifier works well. What will be your next project? How about making a Knightrider LED circuit? Our project is here: http://www.electronics-lab.com/projects/motor_light/035/index.html It makes 6 LEDs light in a back and forth action like this:
  8. audioguru2

    Audio Amplifier from Scratch

    That's right, Quantum, The signal source and the input source are the same thing, and have 2 wires. Connect it using shielded (RCA) cable and the "hot" terminal of the signal/input source connects to the inner wire of the shielded cable and to the amp's volume control or input. The ground...
  9. audioguru2

    Audio Amplifier from Scratch

    Hi Quantum, Don't connect pin 3 of the LM386 to ground, since it is the LM386's input pin. It is shown connected to a "10k" volume control, and your signal source connects to its "Vin" terminal, and the other wire of your signal source connects to ground. Also, don't connect pin 5 to ground. It...
  10. audioguru2

    Audio Amplifier from Scratch

    Hi Quantum, I guess that you know that the LM386 doesn't have much output power, so it won't be very loud before it distorts. The schematics in the applications section of the datasheet show exactly what to do with its pins. The positive terminal of the battery connects to pin 6, and the...
  11. audioguru2

    Passive audio filters

    Hi Vaianajala, That's good that your LPF and HPF have a gap between them so that it will flatten the 3dB peak that is caused when 12dB/octave Butterworth filters have the drivers connected in reverse polarity. It is too bad that the little woofer has such a high inductance so it can't be part of...
  12. audioguru2

    Device to scare mosquitoes..

    I know. Get lots of bats! I see them every evening (I don't know where they live) but I can't hear their ultrasonic "sonar", and I guess that the mosquitoes can't hear them either. Bats eat lots of mosquitoes.
  13. audioguru2

    Boosting Regulator Current/ATX power supply

    Thanks, Ante, If I do a Print Scrn (shifted, so I don't get SysRq), then I don't know where it is stored (Windows Temp. is empty). Then I open paint, and the only action that I have is "Edit - Paste from". Since I don't know where it is stored, then I also don't know where to paste it from. I...
  14. audioguru2

    transistors

    Kevin, If you feed a signal into the low resistance emitter of a transistor, the signal will be divided only if the signal's source resistance is too high. The same thing applies to feeding a signal into the medium resistance (or high resistance if there is an emitter resistor) base of a...
  15. audioguru2

    Boosting Regulator Current/ATX power supply

    Hi GPG, The regulator won't smoke because it has built-in current-limiting and thermal-shutdown. Q2 won't get "too" hot since it never has much voltage across it. Q1 will need a big heatsink since it has nearly the full source voltage across it and plenty of current through it.
  16. audioguru2

    Boosting Regulator Current/ATX power supply

    OOOps, Ante, I wish that I could just copy and paste a piece of a FDF file. This schematic is like your last one, and is from Fairchild, who got it from ON Semi., who got it from Motorola. I think that your 100 ohms doesn't allow enough current for the regulator, so I used 10 ohms. Also, I think...
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Mash, Welcome to our forum. Yeah, your transformer is fine for this 3A-DC power supply. I am sorry that I can't revise the schematic, since I cannot manipulate GIF images. There isn't much difference, just an added 2N3055 and emitter resistors for each one, as shown earlier. Also, the emitter...
  18. audioguru2

    Boosting Regulator Current/ATX power supply

    Ante, Sorry, but what are you doing with a PNP transistor with its collector positive? Shouldn't the current-limit circuit be like this: 1) Normally, Q2 is off. 2) The 7805 passes 70mA through R1, like before. 3) Q1 passes the remainder of the load current, minus the 70mA. 4) When the current...
  19. audioguru2

    EMG circuit

    Hi Jawnail, Welcome to our forum. Is an EMG the kind that attaches to a person with electodes? Your schematic image doesn't show here. What extension (.jpg, .gif) does it have, and have you attached it to your reply?
  20. audioguru2

    Question on the Plants Watering Watcher circuit

    Hi Kiew, I have submitted my new project "Plants Watering Watcher-2". But since it is Saturday evening in Greece, I don't know how soon that Admin can post it. Look for it on the "Home" page. ;D ;D
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