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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    I revised the circuit, not the pcb. Others have done an Eagle pcb. I agree that there should be a place for storing the revised project.
  2. audioguru2

    0-30 Vdc Stabilized Power Supply

    12V at 1W is a current of only 1W/12V= 83mA. Is the current pot set higher than 83mA? When the voltage drops does the current regulation warning LED light up?  Don't change parts without measuring what is wrong. The 2N3055 is simply an emitter-follower that has its base voltage about 0.62V...
  3. audioguru2

    Sound to Light Effect

    1) The first opamp is inverting with such a low input resistance of 1k ohms that it kills most of the signal from the higher resistance electret microphone. This opamp should be non-inverting with a much higher input resistance. 2) The coupling capacitor C4 between the opamps couples positive...
  4. audioguru2

    0-30V Stabilized Power Supply

    The output voltage is supposed to be regulated then it should drop only 0.01V or less when you connect a load. Your output drops a few volts when connecting the load then it is not regulated and needs to be fixed.
  5. audioguru2

    0-30V Stabilized Power Supply

    The voltage regulation is provided by the reference voltage of 10.2V from U1, opamp U2, a driver transistor and an output transistor. The transistors are simple emitter-followers. then a few quick voltage measurements of the output with the malfunctioning occurring will show you what has failed.
  6. audioguru2

    Current monitor/sensor

    The datasheet for your Mosfet will tell you its maximum rated temperature and its thermal resistance.
  7. audioguru2

    Current monitor/sensor

    Simple arithmetic error. 5A x 0.1 ohms= 0.5V. 12V - 0.5V= 11.5V. 5A x 11.5V= 57.5W.The heatsink thermal resistance might be 1 degree C per Watt and the thermal grease might be 0.5 degrees C per Watt. The ambient might be 30 degrees C. Then the heatsink will be very hot and the chips inside the...
  8. audioguru2

    Asking about principle of operation of battery charging circuit

    Nobody uses an old fashioned toxic Ni-Cad battery anymore. Your schematic has the polarities upside down. Usually positive is at the top and negative is at the bottom. 
  9. audioguru2

    Current monitor/sensor

    If the voltage on the (-) input of the opamp is lower than the voltage on the (+) input pin then the output will go positive which turns on the Mosfet more which should increase the voltage at the (-) input AND CANCEL THE INCREASE AT THE OUTPUT. The datasheet for the Mosfet (not ebay fakes?)...
  10. audioguru2

    Current monitor/sensor

    What is the part number of your Mosfets? It should be on your schematic. If the (+) input of the opamp is 0.8V and the current in the 0.5 ohm resistor is 1.6A then the (-) input of the opamp is also 0.8V. When you increase the battery voltage and the current tries to increase then it increases...
  11. audioguru2

    Current monitor/sensor

    If the input voltage does not change but the battery current reduces then the voltage across R4 also reduces and the LM324 opamp inverts and amplifies (minimum DC voltage gain is 25000 times) this voltage drop so that the current change is reduced to almost nothing. Check to make certain that...
  12. audioguru2

    Current monitor/sensor

    The 22 ohm resistors are important. They prevent the Mosfets from oscillating at a high frequency.
  13. audioguru2

    Current monitor/sensor

    You have not updated your schematic so maybe the LM324 opamp is still overloaded. Its output can source only 20mA so maybe the BD139 base current is higher.
  14. audioguru2

    0-30V Stabilized Power Supply

    Your interference is 60Hz but the fullwave rectifiers produce 120Hz so maybe your rectifiers are defective? 60Hz hum pickup from the wiring in your home? 60Hz picked up by a see-through diode (like a 1N4148) in the circuit being shined on by an AC light and acting like a photo-diode? You know...
  15. audioguru2

    0-30V Stabilized Power Supply

    It is 60Hz from your electricity supply, not oscillation. Maybe you built the defective original circuit that has errors and many overloaded parts? The fixed and improved version is at the beginning of this thread. Maybe the tiny overloaded rectifier diodes failed or the transformer has burnt...
  16. audioguru2

    Everything-That-Moves-Alarm

    Maybe the circuit works properly when the coils are raised above the ground.
  17. audioguru2

    0-30 VDC Stabilized Power Supply 0.002-3 A

    There is (or was) a Greek kit available and today there is a Chinese copy of the Greek kit. The kits have a pcb. If you use a kit then you can cross your fingers and hope that one of its many overloaded parts do not fail soon.
  18. audioguru2

    Current monitor/sensor

    Your ground wire is too thin so it acts like a resistor that has a votage drop across it. You need a "star" ground that has all grounds together at one point then there is no ground wire for a voltage to develop across.
  19. audioguru2

    Current monitor/sensor

    I think the very high discharge current in the ground wire is modulating the 0V of the PWM circuit or the opamp circuit. Use a thicker ground wire.
  20. audioguru2

    Current monitor/sensor

    Why are you using poorly filtered PWM instead of variable DC? I don't see any "noise" on the 'scope. Instead I see the filter capacitors charging and discharging. Maybe the signal is a modified sinewave? 
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