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  1. audioguru2

    Horn Sound when The mic is close to LoudSpeaker!

    Hi Shahriar, The sound is caused by acoustical feedback of any sound fundamental frequency (not a harmonic) that has a peak in the system's frequency response, when the microphone can hear the speaker's output and amplify it around and around. It is stopped by: 1) Turn down the gain of the...
  2. audioguru2

    BIG BROTHER!

    I'm not putting you down. I'm saying that your project sounds to be extremely difficult if not impossible to do. I have some scrapped cell phones and their parts are extremely tiny and would be very difficult to remove. Most of the ICs are custom-made for them so information about them is not...
  3. audioguru2

    Car battery Indicator

    Hi Paris, It's a Smartkit. They want you to guess. ;D I think any little diode will work. 1N914, 1N4148 or 1N4002. I didn't translate the article but the LED connected to D4 is probably a green one that is lighted when the battery voltage is high. Then when either of the other two amber or red...
  4. audioguru2

    guide to building sub woofer

    Hi Jojo, Making your own subwoofer is fairly complex because the spec's of the speaker must be matched by the size of the enclosure. There are a few websites that show how to make subwoofers. I have a pretty good stereo system and made a Bass Extension Circuit years ago. Visitors say that it...
  5. audioguru2

    BIG BROTHER!

  6. audioguru2

    6 or 7KW Inverter Needed

    I also think making a 7kW inverter that has a 12V-48VDC stepup SMPS inside it is way over the head of a nooby, since he thinks that by stepping-up the DC voltage then the current will be reduced. Perhaps he should start with making a simple light-dimmer project.
  7. audioguru2

    BIG BROTHER!

    I don't know how you are going to desolder the CCD chip's many tiny close-together pins. I don't know where you are going to find its many support chips, and info about them. I don't know how you are going to make a link that works at microwave frequencies. Good luck.
  8. audioguru2

    high voltage photo flash capacitor charger

    Hi Steven, I'm glad that your relay's coil is 240 ohms instead of the 40 ohms like before. I'm also glad the the 555 has a 12V supply instead of only 9V with a regulator or battery. I suggest that you use a 1N4001 or 1N4002 diode in series between the 555's output and the relay's coil for a...
  9. audioguru2

    Op amp theory Q's

    Hi TG, Attach your schematic so we can see what you are doing. Modern opamps are "perfect" when they are used within their ratings and with their recommended supply bypassing. The series inductance of supply pcb tracks or wiring to the supply pins of an opamp from the supply creates a high...
  10. audioguru2

    Transformer Power Rating

    I disagree. R14 is 1 ohm and is already in parallel with the coil. The pcb shows a diagonal holes layout for the coil to be connected, not for the resistor it is wound on. Maybe the parts list value for R14 is wrong. All power amplifier circuits I have seen use a 10 ohm resistor in parallel...
  11. audioguru2

    I have been thinking

    Hi Zeppelin, The power supply's improvements are still being added as more people build it. Due to the wide tolerance of the control pots, people say the project's voltage goes too high, into rectifier ripple. They also say its current goes too high causing problems. We are thinking of adding...
  12. audioguru2

    Simple 1 hertz clock

    The datasheet for a 555 shows a graph of frequency vs timing capacitor and resistors.
  13. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Yes.
  14. audioguru2

    Laser Parking Aid Schematic

    Wrong! If a laser diode had a voltage of 4.5V and a whopping current of 200mA then it would dissipate 0.9W and melt. If it could be kept cool enough, and sent out only 30% of its power then its laser power would be 0.3W and it could burn holes through things. Please don't just guess, look it...
  15. audioguru2

    typical voltage assignment

    0.8V or less is recognized as a logic low to a TTL input. Most TTL outputs produce a low voltage of 0.4V or less to provide 0.4V of immunity to noise. 2.0V or more is recognized as a logic high to a TTL input. Most TTL outputs produce a high voltage of 2.4V or more to provide 0.4V of immunity to...
  16. audioguru2

    high voltage photo flash capacitor charger

    Hi Steven, You have made a very nice high voltage system. ;D Did you know that a 555 timer doesn't need a regulated supply? Its max is 18V so it will work from a 12V supply exactly the same as it works from 9V. Post the timer's schematic again to see if its output resistor needs to be changed...
  17. audioguru2

    TRIACS-need basic working explanation

    If you call common electronic devices a different name then all you do is confuse eveyone.
  18. audioguru2

    NiMH Charging

    Yes, but they are Ni-Cad, not Ni-MH. In their Ni-Cad applications manual, Energizer shows the results of a test where their Ni-Cads were over-charged for 2 years. Their life and performance was hardly effected. They didn't make the same test on their Ni-MH cells. No. Yes, that is a very long...
  19. audioguru2

    Op amp theory Q's

    I haven't heard any difference, but an inverting opamp doesn't have any (well, hardly any) common-mode voltage swing at its inputs, while a non-inverting opamp has the entire input voltage swing at both inputs. The inputs are slightly non-linear so slightly more distortion is produced in a...
  20. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Yes, 1.5nF is 0.0015uF. Over there, a "green-cap" is marked 152. My blue LEDs require a minimum voltage of 3.2V plus more for a current-limiting resistor. The 3 button cells in a flashlight have the current-limiting resistance built-into them and supply 4.5V. This Whistle Responder project will...
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