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  1. audioguru2

    Current monitor/sensor

    The IC is called and is shown as a high side current sensor but you connected it as a low side current sensor so of course it WILL NOT WORK!
  2. audioguru2

    0-30 Vdc Stabilized Power Supply

    The fixed and modified 3A version of this project uses two 2N3055 output transistors in parallel to share the heat. The 5A version uses three paralleled 2N3055 output transistors. Each 2N3055 transistor has a series emitter resistor so the transistors share the current. They are driven by a...
  3. audioguru2

    0-30 Vdc Stabilized Power Supply

    The original project used TL081 opamps and their total power supply voltage was higher than allowed. Then I changed the opamps to ones that are allowed the high supply voltage. The original project used a transformer that was overloaded and its voltage was too low. I changed it so it works...
  4. audioguru2

    analog ammeters

    I have been in an electronics career for 35 years or more and never needed an analog current meter. About 15 years ago I used the current setting on my digital multimeter only one time and never again to measure and set the pulley on my furnace fan. My digital multimeter can measure just about...
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    This project uses AN OPAMP for its voltage regulation. Its typical DC voltage gain is 100,000 so if the output voltage drops only a tiny amount then it corrects it. Its output voltage should not drop more than 0.03V when its load is increased from zero to 3A. Maybe your project has wrong values...
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    We talked about modifying this circuit for an output up to 30VDC at up to 5A DC a few years ago. It is the same circuit as the latest 3A circuit except the transformer produces more current (7.1A AC), there are three 2N3055 output transistors and R7 is 0.27 ohms at 10W.
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    The improved circuit is designed to supply a maximum output current of 3.0A. It can be modified to supply 5.0A. Ohm's Law calculates that 3A will flow in a resistance of only 12 ohms when the DC voltage is 36V. When the DC voltage is 30V then only 2.5A will flow so your project does not work...
  8. audioguru2

    0-30V Stabilized Power Supply

    There are only two variable resistors, the same as in the original version: P1 sets the output voltage. P2 sets the maximum output current. There are three trimpots that are adjusted only one time: RV1 is the same as in the original version and adjusts the output offset voltage to zero when the...
  9. audioguru2

    Simple O2 meter with LM3915

    Use a voltage regulator and add a fixed resistor to the rheostat so that the voltage to the input of the LM3914 changes as the rheostat resistance changes. Do you know what is the maximum allowed voltage to the rheostat? You do not want it to make a spark that ignites the fuel.
  10. audioguru2

    Common Emitter Audio Amplifier Question

    No. A class-B amplifier produces horrible crossover distortion. Audio amplifiers use a class-AB output stage. I simulated the circuit with an input of 1V peak. With a 12k ohm load the output is pretty good (almost 5V peak). But the 4 ohm speaker seriously overloads the simple circuit and...
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    We talked about the 10uF electrolytic output capacitor having dielectric absorption which might cause the output voltage to rise when it is turned down and there is no load. We recommended using a poly type of capacitor to eliminate this problem. I do not remember anybody talking about using a...
  12. audioguru2

    0-30V Stabilized Power Supply

    Cheap transformers have poor voltage regulation. A Hammond 30V/4A transformer is 30V RMS at 4A. With no load its output voltage is 31.5V RMS so it has pretty good voltage regulation probably because it is huge and its windings have a low resistance. I have a little Chinese 9V/100mA wall-wart...
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    It is [b ]NOT[/b ] an MC4071 which might be a Cmos quad 2-input OR logic gate with 14 legs. Instead it is an MC34071 single opamp with 8 legs.
  14. audioguru2

    0-30V Stabilized Power Supply

    The datasheet for the MC34071 opamp shows its 10k ohms input offset voltage trimpot connected to pin 1, pin 5 and the negative supply almost the same as a TL081 opamp.
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    U2 is an MC34071. Its RV1 input offset voltage trimpot is 10k and is wired as shown on the schematic. Its voltage calibration trimpot RV2 is 20k and is wired as shown on the schematic. The middle leg on a trimpot is its slider which is the middle pin with the arrow of the trimpot on the schematic.
  16. audioguru2

    Lead Acid Battery Long life question.

    If you deeply discharge a lead-acid battery then it is destroyed and might not hold a charge. An ordinary car battery is designed to supply hundreds of Amps for only a few seconds to start the engine then immediately be recharged. It is destroyed by one deep discharge or its life will be very...
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    Kevin, This power supply project is defective which is why I fixed it: 1) It is not reliable since many parts (the transformer, the rectifiers, the transistors and many resistors) are overloaded and burn out. 2) The opamps operate with a total supply voltage that is more than their maximum...
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Transistors with the same part number are not the same. Their hFE and base-emitter voltage are different so one transistor hogs the current and gets hotter which makes it hog more current and get hotter which... (Thermal Runaway). The emitter resistor added in series with each output...
  19. audioguru2

    0-30V Stabilized Power Supply

    R5 is 10k ohms and has only 5.6VDC across it. Then its dissipation is only (5.6V squared/10k=) 0.003W which is nothing and it will not be warm. D5 is a rectifier and it is normal for it to heat slightly.
  20. audioguru2

    0-30V Stabilized Power Supply

    The latest schematic and parts list are here:
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