Search results

  1. audioguru2

    problem Led

    Hi Alun, A Mosfet might not turn-on if the battery was only 3V. The transistor will. I thought of using a darlington transistor but the saturation voltage would be too high with only a 3V supply. Also, a 3V battery's voltage will drop to only 2V over its life. ;D You know what?! You could use a...
  2. audioguru2

    IC output help

    Hi MrFreckles, ;D I've never seen your IC but from the limited info on its datasheet, it should be giving 0% to about 50% (adjusted by your pot) duty-cycle pulses to the Mosfet at about 40kHz, with a max of 5A to the load with your 0.2 ohm current-sense resistor. The transistor and stuff allow...
  3. audioguru2

    problem Led

    I think Ante sells batteries! ;D
  4. audioguru2

    C-E Amp circuit sim using spice

    Hi Walid, Do you think that Spice will show the terrible distortion of your transistor stage?
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Stanley, Excellent! ;D You have a good idea to use trimpots for fine tuning.
  6. audioguru2

    PNP and NPN replacements

    The wavelength of the signal is determined by its frequency so the impedance of an antenna would also change unless you changed the length of the antenna to match.
  7. audioguru2

    pulse generator

    Bill Bowden's voltage regulator circuit would have an adjustable output voltage if you use a 1k pot wired as a rheostat for R2. You aren't powering it from a transformer so replace the huge capacitor on its input with 100uF. Change the output capacitor to 10uF. A zener diode at the output of...
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Correct. The resistance of an ammeter in series with the load would cause a voltage drop at the load. You don't want a voltage drop with a regulated supply. R7 is not in series with the load but is in series with the supply to the project so doesn't affect voltage regulation. Ohm's Law says that...
  9. audioguru2

    Audioguru FM Tx

    Hi Walid, 1) You entered the wrong transistor number into Spice, it should be 2N3904. 2) The frequency response of the preamp is flat from 60Hz to about 600Hz and is boosted above about 1.5kHz due to the selectable pre-emphasis capacitor. 3) My electret microphone measured about 5k ohms so you...
  10. audioguru2

    BJT biasing formulas

    Hi Walid, The voltage gain of a common emitter transistor amplifier stage is RC/(Re+RE). Re is inside the transistor and is small, so the ratio of RC/RE is 10 for a gain of 10. For a fairly low current and a 10V supply, making RC=10k is fine. Therefore RE=1k. ;D
  11. audioguru2

    IC output help

    Your 0.2 ohm current sense resistor limits the load current to only 5A. Your Mosfet is rated for a lot more current so if you can keep it cool enough then reduce the current sensing resistor way down so you can drive high-startup-current light bulbs and motors. You can use a piece of wire as a...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Your 26V transformer might be 28V without a load. It will produce a rectified and filtered positive supply of about 38V, plus the negative supply of 5.6V equals nearly 44V across the TL081 opamps that are rated for an absolute max supply voltage of only 36V. It is risky. More than enough since a...
  13. audioguru2

    3 way speaker system

    Hi Xtp, Of course the power requirement is determined by how loud you want the sound to be. Since your hearing's response to loudness is logarithmic (so you can hear a pin drop and also hear a gun blast), then 100W sounds only twice as loud as 10W. Doubling the power sounds only a little louder...
  14. audioguru2

    LED Resistor Question

  15. audioguru2

    Square wave to Sine wave

    I answered your question in your other post.
  16. audioguru2

    basics of electrical supply

    You never connect the output of an inverter to the mains. As Ante says, the mains would blow it up! You plug a load like some lights into its output. If it powered your whole neighbourhood or city then it would be very overloaded! Maybe you are thinking about a Un-interruptable Power Supply...
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    The project doesn't have a ground. It has a common voltage in its rectifier circuit and a 0V terminal on its output. Pin 3 of U3 is shown on my "0-30V external control" schematic. Pin 3 of the new opamp connects to the output 0V terminal with the other few parts that are connected there. The new...
  18. audioguru2

    pulse generator

    And with the unlimited current you can kiss the little 2N2222 good-bye! ::) ;D
  19. audioguru2

    Electronic Stethoscope

    Hi Xoy, If it is an electret microphone then one of its pins is connected to its metal case and is ground and should be connected to your cable's shield. The other pin is positive and its output which should be connected to the inner wire of your shielded audio cable. ;D
  20. audioguru2

    LED Resistor Question

    Hi Alun, White and blue LEDs are about 3.3V at 20mA. They have a "5V maximum" spec. I suppose a 2.0V or 2.2V red one would have a "3V maximum" spec. My white and blue LEDs measure 3.3V at 20mA and 4.8V with 80mA pulses. They look spectacular and blinding with 80mA pulses, and since they are...
Top