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  1. audioguru2

    Led display Digital Voltmeter question

    Hi Ante, Your full-wave rectifier circuit works fine at low frequencies, I have used it many times. Its "full-wave" becomes assymetrical above about 2KHz, unless you use a wide bandwidth opamp like a TL074, which rectifies well up to about 25KHz in this circuit. The TL074 has FET inputs so RV2...
  2. audioguru2

    3V LED Chaser project

    Hi Guys, I am sorry that I made a boo-boo on my Veroboard layout and pic. I made another project and it didn't work! Besides getting one AA cell backwards (darn Japanese battery cells with tits on both ends), I discovered that I had one extra trace cut (between pins 2 and 13 of the 74HC14). I...
  3. audioguru2

    Tlit switch

    Hi Gugh, That's right, a 555 timer won't time-out if its pin 2 is still being triggered. So your teacher wants you to add another 555 timer to turn off the tilt switch. Are you allowed to be a smarty-pants? How about using the original 555 timer to turn off the tilt switch? Just add a 1K...
  4. audioguru2

    Electronic Stethoscope 2

    Hi Doctor Emad, I have added C7, C8 and R16 to this project so it should operate well with two inexpensive 9VDC/300mA or more "wall wart" power supplies. If mains hum is heard with the volume control at zero, a 47uF capcitor can be added from the LM386's pin 7 to ground which will reduce its hum...
  5. audioguru2

    Tlit switch

    Hi Gugh, Welcome to our forum. What is your problem, did I miss something? Just replace your push-to-make (drawn incorrectly) switch with a tilt switch, which I assume is also tilt-to-make. Then the alarm will sound each time the metal ball inside the tilt switch makes conact wth its conacts inside.
  6. audioguru2

    integrator help

    Hi Gauri, Good, you have an output that resembles a symmetrical triangle wave, but its ramps are exponential (curved) instead of linear. Your 500 ohm value for R4 is so low (it should be megohms) that it takes most of the output current from the opamp so it can't be a current source (which...
  7. audioguru2

    3V LED Chaser project

    Hi again, Here's a pic of a finished board showing the parts and ribbon cables. Also a piece of cut Veroboard with the traces cut. Corrected Nov.12/04
  8. audioguru2

    3V LED Chaser project

    Hi Guys, The project is here: http://www.electronics-lab.com/projects/games/003/index.html I have a pic of my Veroboard layout. It has 47 (!) trace cuts which takes my drill-press about 2 minutes to do. It has 21 jumpers, a few under the ICs, that takes me abut half an hour to cut, bend and...
  9. audioguru2

    LEDs

    Thanks Ante, I fixed it. I thought the sentence looked bad but I was so excited that it moves I wasn't concentrating. Double negatives should never be used. Anglais? I just picked up a brand new but surplus 5V/2A switching wall wart that weighs almost nothing (same as its output cord) and...
  10. audioguru2

    Making basic test equipment, need help.

    Hi Dazza, I first thought of using an LM3914 10-step LED voltage indicator, but even using two cascaded, the output resolution would be very coarse. Perhaps a 10-bucks LCD digital voltmeter module is best.
  11. audioguru2

    Electronic Stethoscope 2

    Hi Del, You are correct, TR1 in my add-on circuit is a transistor, the type depending on the load. It would be hillarious to watch a video of an intruder who is startled by your sound effects and fake tear gas! He would jump right out of his skin. A problem with using a 555 as a delayed...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Ngt, Thanks, that's a nice PCB, especially in vivid red. Who is going to construct and report the performance of the first one?
  13. audioguru2

    integrator help

    Hi Gauri, I'm glad that you have an outout signal but it isn't a triangular integrator waveform. I can see that its output will quickly reach its negative saturation voltage, because the value of the integrator cap is much too small. But I cannot see why the output slowly ramps in a positive...
  14. audioguru2

    LEDs

    Hi Nicolas, The tables for older LEDs do not apply to the new super bright ones. The new ones usually have a much higher voltage requirement especially green, blue and white LEDs. It is best to follow the LED's datasheet.
  15. audioguru2

    Electronic Stethoscope 2

    Hi again Del, Welcome to our community on this website. Now that you have successfully constructed our Electronic Stethoscope-2 project and wish to use it to activate a burglar alarm, I can't remember why you wanted to use a 555 timer IC. I have sketched a simple transistor circuit to be...
  16. audioguru2

    Digital Volume Control

    Hi Giuflex, Sorry, but this project doesn't have a memory so it "forgets" its volume setting each time it is turned off, or the power fails. It draws a massive current so it may be impractical to provide battery backup.
  17. audioguru2

    integrator help

    Hi Gauri, You didn't answer my questions so I am just guessing: 1) A 4.7uF integrating cap takes about 30msec to charge or discharge from the 5V across the 10K input resistor. 1/2 cycle of a 50Hz signal is 10ms. So the cap should be integrating unless my calc is wromg. Try 47uF. Are you certain...
  18. audioguru2

    Terms for Datasheet

    Hi Quantum, Of course a transistor's C-B junction is reverse-biased! The datasheets guarantee a certain maximum (very low) leakage current for it. That's why a transistor turns-off when you ground its base. The collector (N) of an NPN transistor is normally at much higher positive voltage than...
  19. audioguru2

    Digital Volume Control

    Hi Giuflex, I see what you mean. A wire on the left side of the schematic is missing. It connects the output of the 555 at the anode of the LED to the switches. Are you going to make that complicated old project? Its main parts are obsolete, the CD4067 creates a fairly high distortion...
  20. audioguru2

    how can i produce 15kV from 15V DC

    If you don't want to use active devices to step-up your voltage source, get a spark coil from an old car. Apply your voltage source to it through a switch and let your hand be the oscillator. After applying power with the switch, when you turn it off then the coil will make a spark. If you turn...
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