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  1. audioguru2

    500W 12v to 220v Inverter

    The "heat spec's" for a 2N3055 transistor are that it will be at its absolute max temp when it has a PERFECT heatsink that keeps its case at 25 degrees C. Then it can dissipate 115W. A REAL heatsink also has "heat spec's" that are its thermal resistance. Insulators also insulate heat, so should...
  2. audioguru2

    HELP - resistors and dip-switch

    D1 is not necessary since every Mosfet has a very powerful zener diode inside connected like D1. You would use an additional very fast diode if the PWM was at a very high frequency.
  3. audioguru2

    Sound Level Indicator

    Hi Slackjack, An LM3914 has equal 10% steps between its LEDs in a linear sequence. Its range is only 10 times. An LM3915 has 3dB between each step in a logarithmic sequence. Its range is 31.6 times. Your hearing sensitivity is logarithmic in order for you to hear very low level sound and very...
  4. audioguru2

    Digital radar speedometer

    The entire circuit would need to be thoroughly analysed and maybe re-designed. can 74LS be used instead of 74AS? I guess you didn't compare the datasheets: The AS is 5 times to 9 times faster than the LS.
  5. audioguru2

    Digital radar speedometer

    I don't think that the circuit works with its photodiode backwards and without an amplifier.
  6. audioguru2

    audio solenoid and motor response

    A solenoid or a motor cannot move fast enough to make good sound. They are used to vibrate things at low frequencies. You should be able to find an amplifier with enough voltage and current to drive your solenoid and motor, but the inductance is much higher than a speaker which makes high...
  7. audioguru2

    relay question

    Look at its datasheet! Most relays work with 80% or 75% of their listed voltage. A 12V relay is not reliable with a 9V battery for power because the 9V drops to 6V as it runs down.
  8. audioguru2

    About Capacitors

    C3 and C6 are supply bypass capacitors. They keep the supply from bouncing around which  might cause low frequency oscillation (motorboating put, put, put ...) because of the internal resistance of a battery that causes poor voltage regulation. All battery powered circuits should have a supply...
  9. audioguru2

    HELP - resistors and dip-switch

    It is a lousy circuit. The transistors T1 and T2 aren't needed. Pin 3 of the 555 can drive a resistor in series with the timing capacitor and the triangle wave on the capacitor can feed the input of the opamp. I would use a faster, newer opamp or a proper comparator instead of a slow opamp that...
  10. audioguru2

    Veronica PLL

    Buy the kit if it is still available. It will have all the rare or obsolete ICs and odd sized coils and trimmer capacitors.
  11. audioguru2

    Digital radar speedometer

    There is no such thing as "a laser receiving diode". It is just an ordinary photodiode that is sensitive to visible light.
  12. audioguru2

    Power Supply Project needed

    Hi Zeppelin, The LM117 and LM317 operating current goes to the output. The LM117 has a max of 5mA and the LM317 has a max of 10mA. The operating current is the highest at high input voltages. The resistor from its output to its adj terminal, and in series with the adjustable resistor to ground...
  13. audioguru2

    Sound Level Indicator

    Hi Helio, Yours talks and says, "Be Quiet!" when the noise is too loud? Great! ;D ;D Mine just blinks its very bright LEDs with the sounds. Mine has a rechargable 9V battery (actually 7.2V) so it is also portable.
  14. audioguru2

    Simple AM receiver

    Hi Crivoli, Your Q3 is fully saturated when it should be acting as a linear amplifier. It is only a transistor, two resistors and two capacitors. Check or replace them and you will see what is wrong. What transistor part number did you use?
  15. audioguru2

    HELP - resistors and dip-switch

    I can't remember how much current your fan draws, but it is a lot more than what the lousy contacts on your breadboard can handle. What resistor value did you use for the 2N3906 current source? Is the 555 oscillating? Does your power supply voltage drop too low when it is loaded, therefore the...
  16. audioguru2

    Matching IR-components

    The distamce is so short that even the IR diode with the visible light phototransistor will work fine.
  17. audioguru2

    Veronica PLL

    I don't know if a Free Radio Berkley FM transmitter can can have a stereo circuit added. It needs a flat bandwidth of at least to 53kHz for stereo. You can easily make regulated 13.5VDC from a mains transformer without problems.
  18. audioguru2

    Simple AM receiver

    Hi Crivoli, The AM receiver doesn't have an RF filter like ordinary radios have, therefore its output will contain radio frequencies. The LM386 amplifier has considerable voltage gain at AM radio frequencies which must be filtered out at its input with the RC circuit shown in the datasheet and...
  19. audioguru2

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

    Hi Logan, You have a very nice manuscript. It is too bad that you didn't have enough time to fix the faulty circuit by using a CD4069 hex inverter IC. Correction: A Schmitt trigger uses positive feedback, not negative feedback to allow it to switch very quickly even though it has a slowly...
  20. audioguru2

    H-bridge Help required urgently

    Hi Shaiq, Another topic??? Measure voltages when the motor is trying to run: 1) Logic inputs. 2) Power supply. 3) Gates. 4) Drains. Then you will see what is not wired or working correctly.
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