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  1. audioguru2

    Smallest possible LED stoplight circuit

    A CD4017 is a Cmos sequencer IC. It has 10 outputs that go high one at a time one after the other. The outputs can be connected to an LED through diodes so that the red and green lights turn on for a longer time than the yellow. Outputs 1 to 4 have diodes and turn on the green LED for a long...
  2. audioguru2

    Transmitting video on radio FM band

    The bandwidth of the FM transmitter is much too narrow for video. A Video transmitter circuit is completely different.
  3. audioguru2

    Transmitting video on radio FM band

    I have little knowledge in mechanics. How can I modify my cheap bicycle to make it into a luxury car? The very old Greek FM transmitter circuit is completely different to a modern TV video transmitter circuit.
  4. audioguru2

    Re: Music VU Meter

    The first schematic shows green LEDs driven from two LM3916 ICs set for an output current of only 8mA. The input of the IC is a half-wave rectifier so the LEDs average only 4mA when the music is blasting. If the green LEDs are 2.2V and the car battery is 13.8V then each output transistor in the...
  5. audioguru2

    Transmitting video on radio FM band

    An FM receiver has a bandwidth of 150kHz. Video needs a bandwidth of 2MHz to 50MHz. Ordinary old TV used AM, not FM for its video.
  6. audioguru2

    transistor emmiter capacitors

    Yes. Use an unbypassed emitter resistor and use a base resistor fed from the collector and an input resistor that feeds the signal to the base. They both reduce gain and distortion. The first one increases the input impedance. The second one reduces the input impedance.
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    Kevin, This power supply project is supposed to have a regulated output voltage of 0V to +30V and a regulated output current of 2mA to 3.0A. It gets much too hot to use an IC regulator. Its ouput transistors dissipate a max of 113W. A regulator IC in a TO-220 case can dissipate only 18W .
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    The original design used many parts that were too small and got too hot. The new design is almost the same but uses some bigger parts to keep them cooler. Driver transistor Q2 is in a different case and pins layout. Its heatsink probably will not fit on the original pcb.
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    I think somebody made a pcb design of the latest schematic.
  10. audioguru2

    Solar panel output?

    "Full sun" occurs only at noon if the sun is directly straight above the solar panel and it is pointing at the sun. In the morning, in the afternoon, in the spring or in the fall (or winter) the sun is much less bright and the solar panel will produce much less power. 10W is not much power from...
  11. audioguru2

    transistor emmiter capacitors

    Example: The input signal causes the base to go positive. If there is an emitter resistor then the emitter voltage also goes positive which reduces the effective input signal level. That is negative feedback. If the emitter resistor is bypassed with a capacitor then high frequencies will not...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Josko, You are shorting the transformer. The two power supply circuits must be fed from completely separate windings or separate transformers for the negative output of one to be connected to the positive output of the other. Your kind of transformer could be used if one power supply...
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    The 30VAC transformer is needed because of the voltage loss of the main filter capacitor, output opamp, output transistors and current-sensing resistor. Then the output is regulated at 30VDC. Two 2N3055 transistors can dissipate a total of about 140W when the heatsink is pretty big. When the...
  14. audioguru2

    Re: 0-12 Volts LM317 PSU

    An LM317 with a 12V output needs an input of at least 15V. I was mistaken when i thought the output should be 15V then the minimum input must be 18V. A 12V transformwer has a peak voltage of 17V which is reduced to about 15VDC by the rectifiers and filter capacitor. If the output is set to 1V...
  15. audioguru2

    Impedance matching question

    Hi again, Stupen. Like you were told on the other website, the frequency response of your tiny "speaker" is so bad that the low frequency DTMF tones are at a different level from the high DTMF tones. Also, the very low output volume of the 150 ohm speaker when its amplifier is powered from only...
  16. audioguru2

    Re: 0-12 Volts LM317 PSU

    If the output is 1V at 1.5A and the input is 18V then the power in the LM317 is (18V - 1V) x 1.5A= 25.5W. The thermal resistance of the TO-220 case is 4 degrees per Watt and if the ambient temperature is 30 degrees C then the chip will be at (4 degrees x 25.5W) + 30 degrees= 132 degrees C. But...
  17. audioguru2

    transistor emmiter capacitors

    An emitter resistor adds negative feedback to a common-emitter transistor. If the emitter resistor is bypassed then the gain and distortion are increased. If the time constant is short then only high frequencies have boosted gain.
  18. audioguru2

    my mic sounds like this

    Why are you using an old vacuum tube? Is the input device some kind of quartz crystal with Chinese (?) writing around it? Why did you post the sound at a foreign language (French?) website?
  19. audioguru2

    Audioguru's Electronic Stethoscope Help

    Shorting pins 1 and 8 on the LM386 messes up the DC bias. You are supposed to connect a capacitor between pin 1 and pin 8 to increase the AC gain but not mess up the DC bias. Then the gain is 200 in the amplifier IC plus the gain of the preamp which is a lot of gain. You can make an audio...
  20. audioguru2

    Re: 0-12 Volts LM317 PSU

    Not when it has 15V across it because then it will be too hot and a huge heatsink and a fan might not help.
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