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  1. audioguru2

    0-30V Stabilized Power Supply

    Maybe you mean the transformer is 28VAC and 3A? Then without a load it produces a rectified and filtered about +39.6VDC. U1 has a quiescent current of 3.5mA for a TLE2141, then its quiescent dissipation is 39.6V x 3.5mA= 139mW. Its output voltage is 11.2V and its output current is 5.6mA so it...
  2. audioguru2

    Have you ever played?

    Since its control range is only 30m then it is controlled with IR (not radio signals) and it is a cheap little toy.
  3. audioguru2

    Portable Headphone Amplifier Circuit - need help

    It poorly feeds DC through the headphones which is bad for them.
  4. audioguru2

    Have you ever played?

    Will it fly outside when it is a little windy? Or is it for flying indoors in a school gym? Is there a video of it flying?
  5. audioguru2

    0-30V Stabilized Power Supply

    Try a 2A fuse. If it burns out then try another 2A fuse. If it also burns out then use a 3.15A fuse.
  6. audioguru2

    0-30V Stabilized Power Supply

    When the output current is 3ADC then the power is 38V plus 2V of rectifier drops x 3A= 120W. Since your mains is 230VAC then 120W uses 230V/120W= 1.92A AC. Use a 2.5A fuse. I have never seen a PTC thermo fuse. I do not know how accurate they are.
  7. audioguru2

    Transistor problem

    When the PIC output goes high then Q2 turns on and supplies about +4V to R1. It turns on Q1. If your circuit does not do this then maybe you connected the pins on the transistors backwards. Check the pins on the datasheet.
  8. audioguru2

    0-30V Stabilized Power Supply

    Make two completely separate circuits. Even separate transformers and separate bridge rectifiers. The first circuit can make 0V to +30V and the second circuit can make 0V to -30V. Yes, you can connect the positive output of the second one to the 0V of the first one.
  9. audioguru2

    0-30V Stabilized Power Supply

    There is no IC4 in the circuit. Nothing in the project is grounded. If you want a negative supply then use one of these projects and use the positive output as 0V. Then the "0V" output is the negative output. Then make a second project to produce the positive output voltage with its "0V" used...
  10. audioguru2

    0-30V Stabilized Power Supply

    Yes, if each 2N3055 has its own 0.33 ohm emitter resistor.
  11. audioguru2

    0-30V Stabilized Power Supply

    The calculations are simple: A 20VAC transformer might produce 22VAC without a load. Its peak voltage will be 22V x 1.414= 31V and the bridge rectifier will charge the positive main filter capacitor to +29.6V. The TL081 opamps have a maximum allowed total supply of 36V and they still need the...
  12. audioguru2

    0-30V Stabilized Power Supply

    The TLE2141 is made by Texas Instruments who is the largest semiconductor manufacturer in the world. The MC34071 is made by Motorola/Freescale Semi who is also a very large semiconductor manufacturer. They were chosen because their maximum total allowed supply is 44V and they have inputs that...
  13. audioguru2

    0-30V Stabilized Power Supply

    Picmaster, Redwire and a few other people designed the pcb for the improved version of this project.
  14. audioguru2

    0-30V Stabilized Power Supply

    The transformer must be 28V or 30V for the output to be regulated at 30VDC. At 3A your output will be about 26V and will not be regulated because it will be full of ripple because the voltage from your transformer is too low. The circuit does not have simple current limiting. Instead it has...
  15. audioguru2

    0-30V Stabilized Power Supply

    The original project is an old kit. DO NOT BUY THE KIT! Look in the list of topics in the forum for Projects Q/A for two or three threads about the fixed version. Many parts are larger (so they do not overheat) and some wiring is different. Many people posted a revised pcb design in the forum...
  16. audioguru2

    0-30V Stabilized Power Supply

    Since you are using TL081 opamps and a 25V transformer then I guess you made the original project that has problems: 1) Your transformer is probably 27V with no load then its peak voltage is 27V x 1.414= 38.2V and the bridge rectifier reduces it to 36.8V as the positive unregulated supply to the...
  17. audioguru2

    can a pwm create a radio wave?

    PWM switches the power supply to the load on and off, over and over. The duty-cycle of the on time to the off time determines the average power output. If the PWM switches on and off at a radio frequency then it will cause interference in a radio tuned to that frequency. If the PWM is modulated...
  18. audioguru2

    0-30V Stabilized Power Supply

    The original circuit has many parts overloaded. Then the parts will fail soon. The transformer voltage and current are too low. Then the output will not be as high as 30V at 3A. The modified circuit corrected all the problems.
  19. audioguru2

    0-30V Stabilized Power Supply

    Then the diodes are connected backwards or are burned out again. It will not make much difference since the total is only 10% higher. You are probably measuring the resistance of the wires on your multimeter. The 0.47 ohm resistor value is probably correct. Then if your 24VAC transformer can...
  20. audioguru2

    0-30V Stabilized Power Supply

    The two diodes are supposed to conduct a small current which clamps the voltage to -1.3V. Maybe your diodes are connected backwards or maybe they are burned out. R3 is fed a small current from rectifier D6 which has its current limited by R2. The other end of R3 is fed to the voltage-limiting...
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