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  1. audioguru2

    The caps surrounding the LM7812 regulator?

    A voltage regulator IC has a very high internal gain. The external capacitors are use to increase its stability (so it doesn't oscillate) when wires from its input voltage source or to its load are inductive.
  2. audioguru2

    0-30 Vdc Stabilized Power Supply

    Multisim might not understand how the negative 5.6V supply works.
  3. audioguru2

    0-30 Vdc Stabilized Power Supply

    People who made it reported that some parts overheated and failed. Its output doesn't reach 30V at 3A so I investigated and made parts change recommendations to fix it. The revised parts list and reasons for the changes are in this thread.
  4. audioguru2

    0-30 Vdc Stabilized Power Supply

    Two heatsinks of 1 degree C/W would be fine with a fan. You will have 28V to throw away if you use a 12V fan on the 40V unregulated voltage. More heat.
  5. audioguru2

    white led

    I am in Canada. I use American parts. I have never seen parts from ST Micro. The ST13003 is big but will work fine as the smaller high voltage transistor.
  6. audioguru2

    This site is very slow lately

    Have other people noticed that this site is very slow lately? It opens slowly. It navigates slowly. You type a reply then it takes "forever" to post it. Maybe that is why there are not many posts anymore.
  7. audioguru2

    hydroxy gas power supply/separating oxygen and hydrogen from water

    Hydrogen burns with a hard to see blue flame. Sodium added (from bicarbonate of soda or from salt) makes a yellow flame like a sodium-vapour street light.
  8. audioguru2

    NAND gate

    Hi Walid, Cmos gate outputs go to 5.0V or to 0V only if they don't supply any current. With the outputs connected together then one will pull up with its max current of about 2mA and the other will pull down with its max current of about 2mA so the output voltage will be about 2.5V with no...
  9. audioguru2

    IR Headphones

    It is mono, not stereo. It is poor quality and narrow bandwidth AM, not high quality FM. The receiver must be in the direct path of the IR beam. Look at the datasheet for your IR LEDs to see their max continuous current rating. It is probably about 40mA so bias them at 20mA then it will be at...
  10. audioguru2

    NAND gate

    The gates are probably Cmos which have a low output current if they have only 5V for their supply. So the gates are paralleled for double the output current to make enough current for the LED. If one gate tries to make its output high and the other gate tries to make its output low then their...
  11. audioguru2

    Transformerless power supply discussion!

    The last dangerous circuit has too many resistirs and too many zener diodes.
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Valorous, Welcome to our forum. ;D I recommended using the BZX79C zener diode because it is spec'd at a current of 5mA and when the value of R4 is reduced to 1k as I recommended then it operates very well at 5.6mA. The original value of 4.7k for R4 had the zener diode operating at a very low...
  13. audioguru2

    Transformerless power supply discussion!

    With a half-wave rectifier the current will be about half and the ripple voltage will be doubled. If a resistor is added in series with the zener diode then it is also in series with the much higher reactance of the current-limiting capacitor, so the zener diode current or the load current will...
  14. audioguru2

    Transformerless power supply discussion!

    It is a dangerous and bad circuit. Of course there is a problem if nothing limits the capacitor's charging current. If the capacitor is not rated for high currents then it will fail. The fuse limits the current like a resistor. A fuse is a resistor. If a 300 ohm resistor is in series with the...
  15. audioguru2

    VR-sensor opamp input conditioner circuit

    Hi Martin, A TL084 is not a rail-to-rail opamp. Its output voltage goes down to about 1V above ground to about 1V less than its positive supply, when it has a low current load. The minimum supply voltage for a TL084 is 7V. The sensor has an AC voltage that swings above and below ground...
  16. audioguru2

    white led

    I don't use power supplies without a transformer. My mains voltage is half the voltage of yours so I don't know high voltage parts.
  17. audioguru2

    Transformerless power supply discussion!

    Hi Walid, Your mains is a sine-wave that goes from a peak voltage of 311V then through 0V to 311V with the other polarity and continues to alternate. If the circuit is connected to the mains at a moment when the voltage is at a 311V peak and there is not a resistor to limit the capacitor's...
  18. audioguru2

    white led

    the MPSA42 has a voltage rating of only 300V. If your mains has such wild voltage swings as you said then if it "hiccups" then the MPSA42 will be destroyed. A 400V transistor is more suitable.
  19. audioguru2

    Handmade Power Inventer

    Your mechanical circuit doesn't make a sinusoidal waveform. It makes a square-wave with many harmonics just like the output of a 555. It is difficult to make a sine-wave inverter that doesn't get hot. You could make a sine-wave oscillator and feed it to an audio amplifier. The output of the...
  20. audioguru2

    white led

    Hi Pier, This circuit regulates the current for the LEDs. The high power resistor in series with the LEDs is no longer needed because the ST13005 power transistor becomes an automatically adjusted power resistor. Use a medium size heatsink for it so it can dissipate up to 7W.
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