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  1. audioguru2

    IC 555 instead of IC 50240

    The organ kit that uses a 555 square-wave ocsillator makes a buzz tone that is not in tune. The buzz is bang on or bang off like a car's horn. It is a kid's toy, not a musical instrument.
  2. audioguru2

    programming in the RGB led project

    Just use a single type of transistor. Then you can change the bias voltage of the opamps so that each LED dims completely. A BC547 has a max current allowed of only 100mA. A 2N3904 has 200mA. I used 2N4401 which has a max current of 600mA. Any will work with ordinary LEDs since their max...
  3. audioguru2

    RC phase shift

    An incandescent lightbulb is a varying resistance. When the sine-wave is at its peak voltage then the lightbulb's filament is getting hotter so its resistance increases, but with a delay. So if the lightbulb uses the max available current from the sine-wave generator then some parts of the...
  4. audioguru2

    Speed-limit Alert PLEASE HELP!!!!!!!!

    The DC output voltage of the inverter that feeds R8 is a little high, so reducing the value of R8 reduces its DC voltage which makes the inverters following it operate at their most sensitive voltage, and the LED will turn off if there is no signal. The series inverters are biased so that they...
  5. audioguru2

    IC 555 instead of IC 50240

    Hi, An old 50240 made accurate frequencies. A 555 makes frequencies that change. You would need to frequently tune each frequency from each 555 if you want music that is in tune. What kind of sounds do you want? A 555 and most other simple square-wave oscillators make a buzz sound. An...
  6. audioguru2

    Speed-limit Alert PLEASE HELP!!!!!!!!

    Hi Mandavar, The LM2917 has a built-in 7.6V zener diode regulator. A 9V battery quickly drops to 7.2V which is too low then slowly drops to 6V which is much too low. Some of the pins need the regulated voltage. If a low-dropout 5V regulator is added then the voltage might be too low for the IC.
  7. audioguru2

    5 volt to 3.3 volt

    You forgot to say how much current.
  8. audioguru2

    Speed-limit Alert PLEASE HELP!!!!!!!!

    Hi Mandavar, Welcome to our forum. ;D A good place to find out about an IC is from its datasheet: http://www.datasheetarchive.com/datasheet.php?article=1131154
  9. audioguru2

    RC phase shift

    A high current rectified and filtered power supply creates "pits" or "flat tops" in the mains sine-wave waveform when the rectifiers conduct. A light dimmer creates spikes on the mains waveform. Anything electric that turns on or off creates a blip on the mains waveform. If you want lots of...
  10. audioguru2

    Kenwood KR-6400

    Hi John, A copyright thief will probably sell a service manual to you.
  11. audioguru2

    programming in the RGB led project

    Hi Pier, Many years ago I made an analog version of this programmable project. I used 3 very slow oscillators at slightly different frequencies making triangle waves. They drive transistors that drive red, blue and green LEDs. The LEDs slowly brighten and dim at their different frequencies and...
  12. audioguru2

    Gain control

    A volume control pot or any resistor will form a highpass filter and cut low frequencies if the value of the pot is too low or if the input coupling capacitor's value is too low. If the value of the volume control pot is too high then stray capacitance will join it and form a lowpass filter...
  13. audioguru2

    sinewave trouble

    I have looked at the electrical 60Hz sine-wave at the secondary of a transformer with a light load and see all kinds of distortion and interference. Of course a lowpass filter reduces the level of the distortion harmonics and the interference.
  14. audioguru2

    Help me to understand the MC3359P IC

    Hi Walid, I think you have an old cordless phone, the 1st generation. Google doesn't talk about its frequencies anymore. A phone must transmit and receive at the same time so they use different frequencies for transmit and receive. The 1st generation used 27MHz (CB or Citizen's Band) for one...
  15. audioguru2

    sinewave trouble

    Sorry Kevin, That graph is rediculous with its scale of 300dB. Here is one that you can see the harmonics:
  16. audioguru2

    Polar Capacitor as a Diode?

    If a circuit has bias voltages that causes a capacitor to have reversed polarity during part of the waveform then re-bias the circuit to avoid it, use a non-polarized capacitor or connect two polarized capacitors back-to-back like this:
  17. audioguru2

    Polar Capacitor as a Diode?

    We don't make capacitors, we just buy them and use them. We don't connect the polarized ones backwards. I think Google will have lots of articles about capacitors.
  18. audioguru2

    sinewave trouble

    No. All triangle-waves have harmonics. Only a pure sine-wave has no harmonics.
  19. audioguru2

    Good radio

    Each manufacturer has cheap radios and good ones. Sometimes the expensive ones have cheap circuits but many extra features. Enter a radio's model number in Google and search for reviews of it.
  20. audioguru2

    circuits

    Connecting small capacitors adds capacitance when no more is wanted. A large circuit layout has the wires spaced far apart for low stray capacitance between the wires but high capacitance to anything that gets near. Each long wire is a transmitting and a receiving antenna to and from all the...
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