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  1. audioguru2

    Switching Converters

    An inductor makes a high voltage across itself when current flowing in it is stopped, because the collapsing magnetic field cuts across the windings. So the transistor creates a high current in the inductor, then stops the current which makes a high voltage that is collected by the rectifier and...
  2. audioguru2

    0-30 Vdc Stabilized Power Supply

    Just warm is fine, hot is bad. Good. Good. With R4 at 4.7k its current is only 1.2mA so it is barely regulating and its voltage is a little low. Use 1k for R4 and it will be better. A little low, see above. A little low because of above. Good. The current setting pot has a wide range. Your LED...
  3. audioguru2

    Audio Amp

    A 741 opamp will have high distortion when driving an 8 ohm speaker with an output power more than only 1.6mW because its max output current is only 20mA. 250mW from a power amp IC into 8 ohms is a peak current of 250mA. The 741's high frequency response will drop above only 200Hz when it has a...
  4. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Triple, Welcome to our forum. ;D The opamps have an idle power dissipation of only about 200mW so might be a little warm but cetainly not hot. Without a load on the project, U2 still doesn't have much of a load. If it is hot then it is oscillating or something is loading it down, maybe a...
  5. audioguru2

    Decreased Electrical Consumption Question

    Motors are inductive and therefore create a poor power factor which causes currents that are higher than the amount of power that is used. A power factor correction circuit adds a capacitor to reduce the poor power factor. The amount of correction must match the motor but each motor is...
  6. audioguru2

    Audio Amp

    You don't say any parts values. You don't say which IC you used. Your sketch doesn't have power for the electret microphone. If you used an opamp then that is your other problem. An 8 ohm speaker needs hundreds of milliamps. An opamp provides a max of only 20mA. Most opamps should not have a...
  7. audioguru2

    Electret Mic

    You can try connecting the 3-wire microphone like this:
  8. audioguru2

    Electret Mic

    Hi Crivoli, Welcome to our forum. ;D Did you get this microphone? RadioShack never show how to connect their stuff. I think it has a red wire for a filtered positive voltage of 4V to 10V, a ground and a white wire output that connects to a coupling capacitor.
  9. audioguru2

    The small FM transmitter (SMD)

    Hi Ben, Welcome to our forum. ;D Your schematic didn't get attached. 2k7 is the European way of saying 2.7k which is 2700 ohms. They use the letter of the multiplier as the decimal point in case the tiny decimal point isn't printed or copied.
  10. audioguru2

    TV tx

  11. audioguru2

    TV tx

    The transmitter FM modulates a silent carrier since without the carrier there is a lot of noise and when receiving the unmodulated carrier there is silence. The audio circuit works and activates the beeper when there is or is not any noise. The radio receiver circuit isn't shown so we don't know...
  12. audioguru2

    HELP - resistors and dip-switch

    Resistors in parallel have a total resistance that is less than either of them. Of course. The transistor that is driving the motor is switched completely on when it doesn't have much voltage across it so it doesn't get hot, then it switches completely off, when it doesn't have any current so it...
  13. audioguru2

    HELP - resistors and dip-switch

    Sure you can use a selector switch if you use one that selects one resistor at a time. Adjust the trimmer pot then measure its resistance and use a resistor with that value for that fan turn-on temperature as controlled by the switch. The circuit doesn't have a resistor in series with the...
  14. audioguru2

    rf coil

    The inductance and capacitance values are far too high to be resonant at the very high RF frequencies used by cell phones. You don't want resonance anyway because cell phones use a very wide range of RF frequencies. I think: The capacitor just blocks DC so the base of the transistor is at the...
  15. audioguru2

    HELP - resistors and dip-switch

    Hi Virus, In a PWM circuit using a 555 with a speed-adjustment pot, the sensitivity of the pot is reduced by simply adding a resistor or two in series with it. Attach the circuit for us to show you how easy it is.
  16. audioguru2

    simple question about batt chargers

    Walid, This was the 1st time that you said you are charging non-rechargable batteries. I will not discuss it because they are not supposed to be charged.
  17. audioguru2

    rf coil

    I already showed a clip from the datasheet of the 555 timer IC that explains how it works. All that remains is the transistor that amplifies the RF signal and the capacitor that voltage-doubles the supply to a high enough voltage to light the 2V LED.
  18. audioguru2

    HELP - resistors and dip-switch

    Virus said that the switch with resistors controls the speed of a fan controller which is probably a triac circuit for an AC fan. So the current through the switch won't be high but it might have the mains voltage across it.
  19. audioguru2

    TV tx

    Maybe you are not allowed to transmit RF without a permit in your country. Maybe you are allowed to use a 433MHz certified transmitter module that has a short range and can be used by anybody who could also accidently activate your receiver unless you use a secure code.
  20. audioguru2

    Electronic Eavesdropping Devices Detector

    This one has the sound frequency-modulating an IR carrier of about 100kHz:
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