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  1. audioguru2

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

    The voltages should be the same as before except the microphone's voltage should be 1.5V to 2.5V. Did you change the values of R10 and C5? Don't use an LED with this modified circuit. It will stop the oscillator. If you want an LED later then I'll show you how to connect it. What color LED? A...
  2. audioguru2

    Using a pc monitor as a tv

    A pc monitor and a TV are completely different so why would a VCR connected to a monitor do anything? A pile of special parts on a TV card for a pc does all the conversion. You might find a converter circuit on the web but it will be complicated.
  3. audioguru2

    sensitive parabolic michrophone

    Hi Konrad, The resistor at the bottom right is 10 ohms. It is a load on the LM386 at frequencies above 160kHz where the speaker's inductance makes it a very high impedance. It keeps the LM386 from oscillating at a very high frequency. There isn't much ultrasonic power at frequencies so high, and...
  4. audioguru2

    NiMH Charging

    Hi Autir, I have a Ni-Cad powered cordless drill that has been "simple-charging" (about 0.08C) for many years without problems. I worked with wireless boardroom microphones that used series'd Ni-Cads that were always "simple-charging" and when their battery failed I asked the customer, "What...
  5. audioguru2

    BIG BROTHER!

    Start with describing what is the output of your camera. Is it a SVGA pc camera? Have you decided on a transmitter and receiver frequency, RF power, battery voltage and circuits?
  6. audioguru2

    BIG BROTHER!

    The circuit you posted has nothing to do with converting the analog output of a CCD camera to digital. It also has nothing to do with transmitting or receiving the signal.
  7. audioguru2

    LED FLASHER

    No. The capacitors each charge very quickly. Then when a transistor conducts, the positive terminal of the capacitor goes to the +0.1V saturation voltage of the transistor (look on the datasheet) and the negative wire of each charged capacitor is driven way below ground to a negative voltage...
  8. audioguru2

    Speaker Electronis Problems

  9. audioguru2

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

    Electret mics have a metal case. You said yours also has a metal case. Use the ohm-meter function of your meter to measure which terminal connects to the case, it is ground. Also measure that your soldering to the mic doesn't short your 2 wires to it. There are thousands of manufacturers of...
  10. audioguru2

    230V AC to 12V DC @90 AMP

    Hi Awright, I like your oversimplification about a transformer winding with DC on it. I am used to little audio transformers that are not allowed to have any DC applied to them for them to avoid saturation. ;D
  11. audioguru2

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

    Logan, Here's how to wire your electret mic:
  12. audioguru2

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

    Either your meter reads low or the power supply voltage is low. The IC's minimum voltage is 3.0V but might still work if the voltage is a little lower. That is OK. Good, then the IC works fine. Oh, oh. And you can't turn it off. The transistor is blown-up! Don't replace it, the modification for...
  13. audioguru2

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

    Connect the piezo to 3V then reverse the wires and try it again. If it beeps then it is a piezo beeper and can be used in the circuit. I it just clicks when connected and disconnected then it is a piezo speaker and the circuit will need modification to use it. The modification will make it tone...
  14. audioguru2

    230V AC to 12V DC @90 AMP

    63nC converts to 63ns at 1A. That is 315ns at 200mA from the 555. 25 Mosfets in parallel will take 7.9us to charge and another 7.9us to discharge. A full cycle of 25kHz is 40us. So the Mosfets will have roughly half the load's power heating them for 40% of the time. Only 8.6W each, no problem...
  15. audioguru2

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

    It is probably a piezo speaker, not a piezo beeper that has a buit-in oscillator like the project needs. Do you want me to explain how to test it? Do you want me to show you again how to modify the circuit so it can beep? The LED will turn off.
  16. audioguru2

    500W 12v to 220v Inverter

    Hi Rhonn, How are ya doin'? Its great to hear that your inverter operates flawlessly. ;D The expensive Motorola transistors have exactly the same electrical spec's as the cheaper 2N3055 transistors. They use a better mechanical mounting of the chip to the case, or maybe the case is aluminum...
  17. audioguru2

    6 or 7KW Inverter Needed

    The underlined link is a 2kW PWM inverter that uses many high power Mosfets driving two huge paralleled ferroresonant transformers with a sinewave output. Link: http://www.technology.niagarac.on.ca/people/mcsele/i2k.htm Quote: "a software bug led to both sets of FET drivers being switched-on...
  18. audioguru2

    230V AC to 12V DC @90 AMP

    At work, I sent Request For Quotes to transformer manufacturers for a 400W audio output  transformer with a -3dB response from 50Hz to 15kHz. A few samples turned out to be just power transformers with lousy response. One nearly made it and had a good price but the manufacturer didn't have an...
  19. audioguru2

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

    Do you have a voltmeter? Is the supply 3.0V? Do you have a 47 ohm current-limiting resistor in series with the LED? Test if the transistor can turn off by shorting its base to its emitter. +V source is supposed to connect to pin 1. Ground is supposed to connect to ground. Look at the schematic...
  20. audioguru2

    sensitive parabolic michrophone

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