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  1. audioguru2

    0-30V Stabilized Power Supply

    The difference between a 3A project and a 5A project: 1) The 28V transformer must be 119W for the 3A project and must be 198W for the 5A project. A little 28V x 3A= 84W or 28V x 5A= 140W transformer will be overloaded. 2) The 3A version uses two output transistors with emitter resistors and the...
  2. audioguru2

    Led display Digital Voltmeter question

    LCD digital voltmeter modules are inexpensive and work well. But people still want the old-fashined power-hungry LED digital voltmeter circuits.
  3. audioguru2

    0-30V Stabilized Power Supply

    Hi Bean, The original project had many errors so it did not produce 30VDC at 3A but instead produced about only 25VDC with lots of ripple at 3A. Many of its parts overheated especially the old fashioned and tiny transistor Q2 and the transformer. The unregulated supply was a total of 40.3V...
  4. audioguru2

    0-30V Stabilized Power Supply

    The latest version works perfectly but the original version does not work properly. I don't know if an 18V transformer will work without analysing the current in nearly every resistor, then changing some of their values. 18VAC has a peak of 25.5V and the rectifier bridge drops the positive...
  5. audioguru2

    Led display Digital Voltmeter question

    The circuit in the datasheet does not have a resistor between pin 30 and pin 31. I guess it is part of an input attenuator to reduce the sensitivity from 200mV to 2V.
  6. audioguru2

    0-30V Stabilized Power Supply

    I don't know when the latest schematic and parts list were posted so here they are again:
  7. audioguru2

    Led display Digital Voltmeter question

    The circuit in the datasheet is correct. The circuit on this website has many errors. The datasheet says that the IC has a sensitivirty of 200mV full-scale. It shows how to make it 2V full scale. The circuit cannot measure its own supply voltage.
  8. audioguru2

    SImple question on proper diode/LED voltage supply

    Ordinary LEDs are rated at 20mA. With 20mA or 25mA they last 100,000 hours (11 years). After 100,000 hours they might be slightly dim. Their max current is 30mA or 40mA.
  9. audioguru2

    0-30V Stabilized Power Supply

    The latest schematic and parts list have been posted many times. Some people have posted pcb designs for it.
  10. audioguru2

    0-30V Stabilized Power Supply

    The schematic shows which parts are connected to which pin numbers. The layout on the datasheet shows which pins are on which side. Pin 7 connects to the positive supply. Pin 2 is the inverting input that connects to D8 and R4. Pin 3 is the non-inverting input and connects to R5 and R6. Pin 4...
  11. audioguru2

    Servo tester question, need help

    The stupid project does not say its supply voltage. If you look at the datasheet of its PIC micro-controller then you will see that it is 5.0V only. Your 2 cells lipo battery will be 8.4V when fully charged and will drop to about 6V so you need a low-dropout voltage regulator for the PIC.
  12. audioguru2

    questions about FM Superhetrodyne Receiver

    Kevin, Please learn about how a super-heterodyne radio works. It uses a lower frequency fixed frequency IF amplifier (10.7MHz for FM radios) and a radio-frequency mixer. The mixer adds and subtracts the input signal with the local oscillator that is 10.7MHz above or below the input frequency...
  13. audioguru2

    A proposal for using ultrasonic wave bird flock repellents in aircraft

    Jet aircraft engines are designed to "eat" birds because airplane to bird inpacts are common. But jet aircraft and me have never seen a flying elephant.
  14. audioguru2

    A proposal for using ultrasonic wave bird flock repellents in aircraft

    Ultrasonic sound waves have a very short range. Maybe 30m. On an aircraft it will be absolutely useless to scare away birds. An aircraft is extremely noisy and is huge. Are birds deaf and blind??. Birds chase my RC model airplanes around the park. Then my airplanes are chasing them. I nearly...
  15. audioguru2

    LM338 Power Suply Current Regulator

    No because your input supply voltage is too high and the LM338 current regulator will overheat when it regulates the current between 1A and 5A and when the output voltage is set low. If the input voltage is 38V, the current is set to only 1A and the output is set to 4.75V then the LM338 current...
  16. audioguru2

    0-30V Stabilized Power Supply

    I am assuming that your your unregulated supply is +40V. If U1 is an MC34071 then it has an idle current of 2.8mA max which causes heating of 40V x 2.8mA= 112mW. U1 has an output of 12.2V and an output current of 5.6mA so it heats with an additional (40V - 11.2V) x 5.6mA= 161.3mW. Then the total...
  17. audioguru2

    0-30V Stabilized Power Supply

    The current regulation pot sets the max amount of current the output of this power supply can provide. RV3 calibrates the max current to be 5.0A. At zero rotation the warning LED should not light if there is no load. At half-way rotation the warning LED should light and the output voltage should...
  18. audioguru2

    LM338 Power Suply Current Regulator

    Your problem is that your high supply voltage range and high output current will cause the LM338 current regulator to reduce its max current  to only 1A and overheat. If the LM338 current regulator has an input voltage of only about 13.2V then it can supply a max current of 5A when the LM338...
  19. audioguru2

    ghost detector circuit, 3 volts buzzer adition

    Hi Steven, Don't you have a spelling-checking program? Your spelling is so bad that it is difficult to read what you say. No Speeky Zee Enrgish??
  20. audioguru2

    LED VU meter question

    I don't see a 7.5V circuit nor a 6V circuit in this thread. I used a "9V" Ni-Cad battery that is actually 7.2V. Then when the battery failed I replaced it with a Ni-MH "9V" battery that is actually 8.4V. I used two 1.8V red LEDs in series at each output and the current is 26mA at each output...
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