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  1. audioguru2

    H BRIDGE, driver for a dc motor

    You forgot to attach your schematic.
  2. audioguru2

    1.2 V PWm Signal

    You don't want a 1.2V PWM signal. The datasheet shows an open-collector transistor that is fed from any current-limited voltage signal. The open-collector is used so that the ADJ pin voltage does not exceed the reference voltage that has a tolerance. The IC is supplied from a higher voltage...
  3. audioguru2

    Feed back amplifiers

    There is negative feedback and there is positive feedback. What are the other two types of feedback??
  4. audioguru2

    Anyone can explain the "digital voltmeter" circuit to me?

    Hi EE, Welcome to our forum. ;D The ICL7107 IC has a very high input resistance. The range switching for a voltmeter that uses it should use very high resistor values. Our projects don't. Our "Digital Voltmeter" project uses a 10 ohm resistor in series with the input on one scale, then a 2k...
  5. audioguru2

    telephone transmitter again not working??

    If you are far from the telephone exchange then your off-hook voltage will be low enough to operate a single telephone. If the phone draws a high current and you are far from the exchange then your voltage will be too low to also power the bug transmitter. How can you modify your telephone...
  6. audioguru2

    plz help me in getting the pin configuration of IC ZN414

    On another forum the guys were saying that their cities don't have AM radio stations anymore. I remembered Singapore was one. I am also old but I love the crystal clear and wide frequency response of FM radio. Hi-fi's and car radios have AM radios only because the government forces them to have...
  7. audioguru2

    plz help me in getting the pin configuration of IC ZN414

    Hi IC, Welcome to our forum. ;D The old ZN414 was a very poor quality AM radio circuit. Does anybody listen to lousy AM radio anymore? A real AM radio uses a lot more parts than a ZN414 IC. You can see the details of the ZN414 and any other electronic circuit or transistor from its datasheet. I...
  8. audioguru2

    telephone transmitter again not working??

    The telephone transmitter is modulated by the fluctuations in the telephone line. If you stabilize the voltage then it won't be modulated. Maybe it can have a voltage regulator then the RF oscillator could be fed through a 620 ohm resistor and have the audio from the telephone line...
  9. audioguru2

    telephone transmitter again not working??

    The radio frequency of the telephone FM transmitter depends on the supply voltage from the telephone line and the current of the phone you are using with it. My FM transmitter has a known radio frequenvy because its oscillator has a 5V voltage regulator. Everty phone line has a different...
  10. audioguru2

    How does one measure frequency response?

    The frequency response of a modern audio power amplifier is absolutely flat from 20Hz to about 100kHz. The frequency response of good speakers is within 3dB from 40Hz to 18kHz. The frequency response of poor speakers is all over the place and is not flat. Poor speakers have a few resonant peaks...
  11. audioguru2

    telephone transmitter again not working??

    Sorry, Your pics are too fuzzy to see anything wrong with your project. I designesd and made my FM transmitter (the second one I have ever made) and it works perfectly:
  12. audioguru2

    charging a Battery and using it at the same time

    Hi Abu, LEDs don't have a set voltage. They have a range of voltages. It might be 1.0V for one and it might be 1.4v for another. If these two are connected in parallel then the lowest voltage one will take all the current and burn out, then the other one will burn out. So LEDs should never be...
  13. audioguru2

    555 astable monostable

    The capacitor does not "ground" pin 5, it filters it.
  14. audioguru2

    charging a Battery and using it at the same time

    LEDs do not operate from voltage, they operate from current. Lightbulbs operate from voltage. Each LED needs to have a current-limiting resistor in series with it. If the minimum battery voltage was higher then two LEDs could be in series and in series with a current-limiting resistor. Post...
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Somebody who has the project made with the slow TIP31A driver transistor could 'scope its output while it was loaded and unloaded with a 3A load. IC voltage regulators have overshoot and ringing at their outputs but the capacitor to ground on their output reduces it very well. The LM723...
  16. audioguru2

    RC mini Helicopter

    Last weekend I watched many electric model RC airplanes fly. One was a big bi-plane that suddenly slowed and developed a smoke trail. The guy landed it quickly then plucked out its badly smoking Li-Po battery that he recently bought for $500.00. The battery produced a lot of white smoke for a...
  17. audioguru2

    RC mini Helicopter

    Radio control circuits for model airplanes and model helicopters are standard and easy. New tiny and lightweight receivers are available. The mechanics of a helicopter is a nightmare. Flying a helicopter is also a nightmare.
  18. audioguru2

    help

    Ordinary TTL has a max input low current of 1.6mA. Ordinary Cmos has a minimum output low current of only 0.5mA (with a 5V supply) so Cmos cannot drive TTL. The max input low current of LS-TTL is 0.4mA so ordinary Cmos can drive one LS-TTL input low. Ordinary TTL has an output high voltage that...
  19. audioguru2

    TDA2005 making static noise

    Hi Wellington, Nothing in your schematic will produce an oscillator. Maybe something is connected where it should not be connected.
  20. audioguru2

    TDA2005 making static noise

    hi Wellington, The circuit will probably be without interference if it is mounted in a grounded metal box.
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