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  1. audioguru2

    ...about the 25W MOSFET(or HEXFET) amp...again...

    Hi Sasi, 1) I would remove R14, R15 and R18. 2) The driver transistor and its current source are designed to provide a very small current for the Mosfets' gates but not enough current to drive bipolar output transistors. Maybe the output transistors should be darlingtons to operate with the low...
  2. audioguru2

    latching

    Here's a discrete alternate-action circuit that also doesn't use any supply current when it is off. R1 is designed for a 1V supply and must have its value increased with higher supplies.
  3. audioguru2

    4W FM Transmitter

    Hi Sasi, Your very nice ground-plane antenna is strong enough to withstand a hurricane (monsoon?). Are the lengths 1/4 wavelength? I might be incorrect, but I figure that a dipole has 3dB gain over a whip antenna and your ground-plane has 3dB gain over a dipole and is omni-directional. Therefore...
  4. audioguru2

    My laptop the firebomb

    I might take it apart very carefully outside. Put it in a bucket and throw lighted matches at it!  ;D
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    What is a "proof tip"?
  6. audioguru2

    PWM

    Hi Alun, Yeah, my circuit is very similar to Ante's.  ;D
  7. audioguru2

    PWM

    Hi Ante, My PWM oscillator is at 3.9KHz so when it is fully dimmed, the off pulse width is 256us and the on pulse width is probably only 245ns! A totem pole (push-pull?) output would probably speed the turning off somewhat and help dim the LED, but maybe it wouldn't be enough. The dimming occurs...
  8. audioguru2

    My laptop the firebomb

    Hi Ante, Thanks for warning me. I was nearly ready to cut one open with my hacksaw.  :o
  9. audioguru2

    PWM

    Hi Ante, An incandescent light bulb is dimmed to off with maybe 10:1 PWM of its bright operating current. A loaded motor might stop with 20:1 of PWM. But my ultra-bright LEDs are still very visible with only a few microamps of current. In my chaser I dim with PWM to about 1047K/1K where the 1K...
  10. audioguru2

    PWM

    I used an "audio taper" logarithmic brightness control in my Chaser projects for smoother control of the approx 1000:1 of their dimming. Even with 1000:1, the LEDs weren't completely dimmed and I had to add a capacitor to squash the remaining extremely narrow pulses.  ;D
  11. audioguru2

    Buried wire detector

    Hi Kiwi, That's great that your new coil and higher frequency are much more efficient!  ;D The opamps for your two sensors should be amplifying the sensors' signals and not oscillating. The power in your transmitter coil must be reduced so that the receiver's opamps don't "clip" but have a...
  12. audioguru2

    R/C toy car transmitter

    Your link doesn't work. By shortening it, I got to Elenco's website and found the manual. If you try to increase the RF output power, it might melt Q2 and might be illegal because it would cause interference to other RF.  :'(
  13. audioguru2

    latching

    These ones:
  14. audioguru2

    Transistor distortion and reducer circuit

    I found this info about the horrible distortion of a transistor without negative feedback. I have seen the distortion many times on my 'scope but didn't measure how much. Here the distortion is shown to exceed 15% and shows a way to reduce it without adding negative feedback which would also...
  15. audioguru2

    Lie Detctor

    I looked at the datasheet for the transistor I recommended in Google, and I found all kinds of important information that you need:
  16. audioguru2

    Lie Detctor

    If your transistor is a PNP it won't work in this circuit anyway. You might as well purchase a cheap one that is the correct type. RadioShack transistors are usually marked on the package which wire is which for people who don't have access to Google to look it up.  ;D
  17. audioguru2

    Lie Detctor

    Hi Cody, A potentiometer (pot, or volume control) is a variable resistor. Its squiggley line is its resistance and its arrow is the slider that slides along its resistance part. I have never seen your before but I think that its slider is the upper right pin. Connect it to one of the other pins...
  18. audioguru2

    Lie Detctor

    Hi Cody, An audio pot will work, but have most of its adjustment range crammed at one end. It has only 3 terminals. The schematic shows to connect its slider, the middle terminal, to one end. Try it with the middle terminal connected first to one end, then try it with it connected to the other end.
  19. audioguru2

    Solder Fumes

    Hi Prateek, That is how I solder a wire on a pcb. I hold the cleaned tip (wiped on a damp grooved sponge) of the soldering iron against one side of the joint for about 1/2 second. Then I touch the rosin flux cored solder to the other side of the joint and it flows around the joint in another 1/2...
  20. audioguru2

    Buried wire detector

    Hi Kiwi, 1) Change the frequency of the 555 by reducing the value of its timing cap by dividing its existing 100Hz value by 50. Then "tune" your pickup coil to 5KHz with a capacitor in parallel. Then tune your amp to 5KHz with a bandpass filter or use a highpass filter. 2) I am glad that you...
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