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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    There were never 3 calibration trimpots. Only two were added, one for max voltage and one for max current. I think the latest schematic is the same as the one in 2008 except two calibration trimpots were added. Simply remove them if you don't want them.
  2. audioguru2

    Electronic Stethoscope

    Since you don't know the function of each component in this very simple amplifier circuit then you don't know the basics of electronics. Your teacher will probably cut the circuit apart: 1) The mic is an electret type that you can read about in Google. It must be powered from a filtered supply...
  3. audioguru2

    Electronic Stethoscope

    The word "working" is not the word that you should say in English. If you want the circuit description that tells how the circuit functions then it is in the project's text.
  4. audioguru2

    Electronic Stethoscope

    If you want a job then you must look for a job. Maybe your friends and family can help you find a good job. What is an externel? Your English and spelling are horrible.
  5. audioguru2

    Electronic Stethoscope

    I cannot understand what you say because you do not talk in English words. The jack at the output is for over-the-ears headphones. "Open" earphones or a speaker will be heard by the microphone and will cause acoustical feedback howling. Look at the new project in the Projects section on this site.
  6. audioguru2

    Electronic Stethoscope

    Many years ago the project was defective with many errors and did not work. It used five 741 opamps. I corrected the errors and removed the third opamp which did nothing. The preamp and lowpass filter opamps are now a low noise dual opamp (TL072), the fourth opamp that blinks the LEDs is a 741...
  7. audioguru2

    0-30V Stabilized Power Supply

    I find having a coarse control and a fine control is a nuisance. There is always one of the controls at its end but more adjustment is needed so a few adjustments on both controls is needed for one setting. My power supply has a knob for voltage that is 40mm in diameter and I can set it to very...
  8. audioguru2

    0-30V Stabilized Power Supply

    You can use 10k and 1k pots in series. I would just use a big knob on one pot.
  9. audioguru2

    CO2 Measurement Stuffy air alert

    The  article came from India so maybe people there live inside sealed plastic bags? In Canada, homes have a heat exchanger so that stale air is vented but its heat warms incoming fresh air in winter and cools incoming fresh air in summer. My high efficiency furnace and fireplace use outside air...
  10. audioguru2

    Please help me to build-up this circuit

    You can use a triac to replace a relay in an AC circuit if the triac is sensitive enough and you know how to design it.
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    What are you asking talking about? 1445 was 556 years ago.
  12. audioguru2

    Please help me to build-up this circuit

    The 7805 regulator needs the input and output capacitors shown in its datasheet.
  13. audioguru2

    Please help me to build-up this circuit

    The transformerless circuit is made to drive one LED at 20mA and cannot supply enough current for your relays. An AC-DC "wall-wart" power supply plugs into and hangs on the electrical outlet and its thin output cord goes to your circuit that hangs on the wall.
  14. audioguru2

    Please help me to build-up this circuit

    You should use a power transformer because your circuit is dangerous. Transistor T1 will never turn off because the TSOP1738 output goes high to +5V and the emitter of T1 is at +9.1V. Operate the CD4017 and the emitter of T1 at +5V from a little 78L05 regulator so that T1 can work properly. The...
  15. audioguru2

    switching speakers (4 conductors per) 10 + with IC's ???

    A solid state relay uses a triac or couple of SCRs. It would produce horrible crossover distortion if it switched a speaker to the output of an amplifier.
  16. audioguru2

    Help please about the very simple power failure light project

    Why are garbage and dangerous projects like this one in our projects section??
  17. audioguru2

    Help please about the very simple power failure light project

    The 470uF capacitor has a 1N4742A zener diode across it. I looked up the datasheet for the zener diode on www.datasheetarchive.com and found out that it limits the voltage to 12V. I would use a 25V capacitor for it to last a long time. The 1.2k resistor does not have a power rating. It will...
  18. audioguru2

    Stereo Power Supply Core Problem

    The core is supposed to be laminated in many layers and the layers must be insulated from each other with enamel paint or something. Maybe you scratched the laminations and caused them to be shorted together. Then eddy current flow in them and cause heating. A microwave oven transformer is...
  19. audioguru2

    1 Simple question about led drivers

    The website is in Germany which explains why English details about their LED fader circuits is missing. Maybe they should show a video of what their product can do.
  20. audioguru2

    Window Car circuit

    You don't make an amplifier to drive a DC electric motor. You simply feed more voltage to it. But it is difficult to make a voltage boosting circuit because then the current would also be increased. Then the motor, its fuse and its wiring will burn out. The gears will quickly wear out.
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