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  1. audioguru2

    inverter

    You don't understand that the waveform of a modified sine-wave or modified square-wave inverter is simply a square-wave with a peak on the positive-going portion and another peak on the negative going portion of a square-wave. The peaks are to make the average peak voltage the same as the peak...
  2. audioguru2

    inverter

    No. The datasheet for a 555 shows that Pulse Position Modulation also changes the frequency while changing the pulse widths. PWM is not supposed to change the frequency. No. The frequency of the PWM pulses is very high so a simple LC 12dB/octave filter smooths the pulses into a pure sine-wave...
  3. audioguru2

    0-30V Stabilized Power Supply

    For a DC output of 3A, the transformer must supply 4.2A AC. C1 must have enough capacity to filter properly. Did the warning LED for the current regulator turn on? Current regulation is done by reducing the output voltage. Maybe the current setting was too low for 3A. U2 is the voltage...
  4. audioguru2

    reshaping a signal

    Hi Walid, You should attach your sketch here with your post instead of posting it on a website in your country. Integrate the waveform or use a lowpass filter. Then use a schmitt-trigger to square it.
  5. audioguru2

    0-30V Stabilized Power Supply

    in the latest version, the output of U3 drives D9 to reduce the output voltage to zero when the output is shorted. D9 has a forward voltage drop of about 0.7V so the output of U3 must be able to go a little below -0.7V. I used two diodes to make the negative supply for U3 at about -1.3V. A 3V...
  6. audioguru2

    inverter

    You are wrong, Kevin. PAM wastes a lot of power. PWM does not. I worked for 15 years with a very high quality Norwegian very large intercom system. It used PAM and was called Pamex. The amplitudes of the audio was sampled at a high frequency and the samples had their own time slots. Each audio...
  7. audioguru2

    0-30V Stabilized Power Supply

    Hi Morpheous, You should attach your photos here with your reply because ImageShack takes too long to load. The latest version uses 2N3055 transistors in a TO-3 steel case because their max allowed dissipation is 115W each (with a perfect heatsink). Your little TIP3055 transistors are in a...
  8. audioguru2

    0-30V Stabilized Power Supply

    Yes.
  9. audioguru2

    0-30V Stabilized Power Supply

    Hi Clemens, 1) The 11.24V output of U1 is perfect. 2) The output of U2 goes to +31.5V which is good. Then the output of the project should go to +30.5V without a load and to maybe +25V with a 3A load. 3) The output of U3 is normal. 4) The emitter voltage of Q2 is very wrong. It is an...
  10. audioguru2

    0-30V Stabilized Power Supply

    Hi Clemens, The original version of this power supply had many parts that were overloaded. So I fixed it. I would guess that the overloaded Q2 transistor (2N2219) on your project has failed but it also could be the output transistor Q4 or any of the opamps that have a supply voltage too high for...
  11. audioguru2

    inverter

    Mains electricity in your home is made with a mechanical windmill, water tubine in a river or steam turbine heated with coal, natual gas or nuclear. Its waveform is a smooth sine-wave at the low frequency of 50Hz or 60Hz. An inverter operating from a battery can use a sine-wave oscillator and a...
  12. audioguru2

    0-30V Stabilized Power Supply

    It is normal for the current regulation to be turned on without U1 in place.
  13. audioguru2

    0-30V Stabilized Power Supply

    C3 on my schematic filters the -1.3V supply which has nothing to do with opamps blowing up. With C3 shorted then the current regulation will not work if the output of the project has a very heavy load at a very low voltage or if the output is shorted. Then U2 might blow up and Q2, Q4 and Q5 also...
  14. audioguru2

    Sound Level Indicator

    With no sound, pin 5 of the LM3915 is supposed to be 0.00VDC, not 5.0VDC. It becomes 5.0VDC only when the sound picked up by the micophone is loud. Maybe the preamp is picking up mains hum. I used a shielded audio cable only 2cm long from the mic to avoid the cable picking up mains hum. If you...
  15. audioguru2

    Sound Level Indicator

    Hi Adam, I used a low-dropout 5V regulator because sometimes my project is powered from a Ni-Cad "9V" battery that is actually only 7.2V and its voltage quickly drops to 6V that is too low for a 78L05 regulator. When there is no sound, pin 5 of the LM3915 is fed 0V from the emitter of Q2. The...
  16. audioguru2

    0-30V Stabilized Power Supply

    Not in the new circuit. It was used 5 years ago in the first fix of this project.
  17. audioguru2

    0-30V Stabilized Power Supply

    Your project probably has the output of U3 shorted to ground or to the negative supply. Maybe the U3 opamp is already blown because it is not supposed to get hot.
  18. audioguru2

    0-30V Stabilized Power Supply

    U1 has a light load so it should be cool. U2 has a little more work so it should be warm. U3 has a light load so it should also just be cool. Since U3 has a light load then the 10V zener diode that powers it should also be cool. P2 is the current-setting pot. Its voltage is simply a reference...
  19. audioguru2

    0-30V Stabilized Power Supply

    The 24VAC transformer at 5A is 125VA. Its peak voltage to the rectifiers is 40VDC and it is overloaded when the DC current exceeds 125/34= 3.7A. The max output voltage at 3.7A will be about 25VDC.
  20. audioguru2

    0-30V Stabilized Power Supply

    For a 5A output at 30V, the transformer must supply a peak DC voltage of about 39.6V to the rectifiers at 5A which is 198VA. You can use a 28VAC transformer or a 30VAC transformer at 7.07A. The modification to the latest 3A schematic for a project with an output of 5A is to add a 3rd 2N3055...
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