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  1. audioguru2

    0-30V Stabilized Power Supply

    The 3A version of this improved project uses two 2N3055 output transistors. The 5A version uses three of them. They share the heat. When the output is shorted or set to a low voltage and the current is 5A then the output transistors must dissipate a total of about (40V - 1.35V - 0.55V) x 5A=...
  2. audioguru2

    1-18volt variable power supply

    Most digital oscillators produce a square-wave that has many harmonics. All the harmonics are odd and none are even because a square-wave is symmetrical. If the square-wave has a high enough frequency then you can filter it into the fundamental sine-wave.
  3. audioguru2

    0-30V Stabilized Power Supply

    You want 12V at 2.5A. Then Ohm's Law says the load is 12V/2.5A= 4.8 ohms. You set the voltage to 12V and you set the current regulator to 2.5A and load it with 2 ohms. Then Ohm's Law says the voltage MUST be 2.5A x 2 ohms= 5V as shown with Ohm's Law again. If the voltage stayed at 12V then the...
  4. audioguru2

    1-18volt variable power supply

    You did not post a schematic in this reply so we do not know what you are talking about. This thread was for a power supply, not about an oscillator anyway.
  5. audioguru2

    1-18volt variable power supply

    You deleted your Cmos "oscillator" now this thread makes no sense. Why do you say the output current of a Cmos inverter is too high without looking at its datasheet to see that it is actually fairly low?
  6. audioguru2

    1-18volt variable power supply

    If it works then the 680uf capacitor will take 113 minutes (nearly 2 hours) to partially charge by the 10M resistor and will be fully charged in 9.4 hours when the oscillator might start. Why don't you make a NORMAL Cmos oscillator like these ones:
  7. audioguru2

    1-18volt variable power supply

    Where is 20V regulated going to come from? A 20V zener diode has poor voltage regulation and its voltage increases when its temperature increases as it warms up. As I said before, a 5.6V zener diode has very good voltage regulation and its voltage does not change when the temperature changes...
  8. audioguru2

    0-30V Stabilized Power Supply

    Good, you fixed it. If the current regulation circuit works properly and the BD139 and 2N3055 transistors have enough heatsinking then the output current will be what the current-setting pot makes it from a few mA to 3.0A and the LED will light.
  9. audioguru2

    1-18volt variable power supply

    No opamp in the circuit has a gain of 3. Also there is no voltage follower opamp. Opamp U1 has a voltage gain of 2 so that the 5.6V zener diode is amplified to make the 11.2V reference. I told you before why the 5.6V zener diode performs much better than one with a higher voltage. Opamp U2...
  10. audioguru2

    5.1 channel schematic diagram

    The most important specification for a power amplifier is how much power it can provide at low distortion. You forgot to say how much power you need. The project should be easy to find in Google.
  11. audioguru2

    1-18volt variable power supply

    No. A non-inverting opamp does not have a series input resistor Ri. It has a feedback resistor Rf and another resistor from the inverting input to ground. The non-inverting input is fed from a pot dividing the reference voltage.
  12. audioguru2

    1-18volt variable power supply

    If your main opamp is non-inverting then the second opamp (the feedback opamp) is not needed. Then the feedback goes from the output to the (-) input of the single opamp. You can add two resistors to the feedback so the circuit can amplify a very good 5.6V zener diode up to 18V. Or you can...
  13. audioguru2

    9V BATTERY CHARGER CIRCUIT

    Your batteries ARE NOT 280mA. They are 280mAh which is not their maximum current, it is the current they can provide for one hour. Their maximum current might be a few Amps for less than 5 minutes. If you use a 10V zener diode then the diode at the output of the charger will reduce it to 9.3V...
  14. audioguru2

    1-25volt variable power supply

    Please post its schematic and parts list.
  15. audioguru2

    9V BATTERY CHARGER CIRCUIT

    Of course the battery connects to the output, not the input. The circuit limits the charging to (9.1V - 0.7V for the diode)/15mA, plus or minus 5%. But which kind of battery? A 7.2V Ni-Cad or an 8.4V Ni-MH? A 7.2V Ni-Cad has 6 cells and charges to 8.4V so 8.4V (it might be 8.0V) might be too...
  16. audioguru2

    0-30V Stabilized Power Supply

    But the output of your project is at 36V which is 7.2V higher. If the base or emitter of one or both of the output transistors is shorted to the positive unregulated supply then the emitter-base diode of the BD139 is reverse-biased and acts like a 7.2V zener diode. After fixing it then maybe...
  17. audioguru2

    0-30V Stabilized Power Supply

    Hi Sulphuric Acid, I have Picmaster's schematic. He changed ALL the parts designation numbers.
  18. audioguru2

    1-18volt variable power supply

    Kevin, 1) Why did you make a heater since the 36V input is much too high for your 18V power supply? To make 18V then an input of 24V maximum can be used and it will be much cooler. 2) Why did you use such a high voltage zener diode? A high voltage zener diode has its voltage increase a lot when...
  19. audioguru2

    0-30V Stabilized Power Supply

    What is "mcp"? It should be an MC34071 or a TLE2141. Perfect. The +11.2V feeds the voltage setting pot whose slider moves from 0V to +11.2V. The slider feeds opamp U2 and it has negative feedback from the output of the project setting its voltage gain at 2.68 times. The driver and output...
  20. audioguru2

    0-30V Stabilized Power Supply

    You might be using old TL081 opamps that have failed because the unregulated supply voltage is too high for them. You might have the pins on the driver or output transistors connected backwards. When the problem is fixed then you might find opamp U2 destroyed from excessive heat.
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