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  1. audioguru2

    LED VU meter question

    You probably want to drive the VU meter from the output of your MP3 player so that the volume control on the amplifier does not affect the range of the VU meter. The LM391x ICs have an adjustable voltage reference using pins 7 and 8. When pin 8 is connected to ground and R2 is not used then the...
  2. audioguru2

    0-30V Stabilized Power Supply

    The two 2N3055 transistors operate at up to 1.5A each in this project, not only 2.5mA. You are probably just measuring their leakage current. At 1.5A their minimum hfe is about 46 so the max current in the BD139 is 3A/46= 65mA. I don't know why you have four output transistors when only two are...
  3. audioguru2

    0-30 Vdc Stabilized Power Supply

    With an input voltage that is much lower than the design needs, you must analyse each and every part value to see if the voltages and currents are too low. The negative supply voltage will probably be too low and will need to have its current increased to increase its voltage which will cause...
  4. audioguru2

    0-30V Stabilized Power Supply

    The calculations are simple so you should do them since you want to change the project. 1) Look on the datasheet of the 2N5886 transistors to see their minimum hFE at whatever max current you want. Divide the max output current by the minimum hFE to calculate the max collector current for the...
  5. audioguru2

    Flashing/Blinking LEDs

    A parallel resistor does not restrict the voltage, it simply wastes battery power. LEDs need their current limited, not their voltage. Leds set their own voltage because they are a forward-biased diode. If you have a simple flasher circuit then make one for each LED. Electrolytic capacitors have...
  6. audioguru2

    0-30V Stabilized Power Supply

    every transistor is different even if they have the same part number. Maybe you could buy a few hundred transistors, test them all then use the ones with the highest current gain.
  7. audioguru2

    the same Voltage ,but diffirent Current frequency ,can it work?

    If it is powered from 6VAC/400Hz then the main filter capacitor must have its value increased 8 times if a 50Hz frequency is used. It might be easier to power it from a DC wall-wart if you can measure how many DC volts it needs.
  8. audioguru2

    0-30V Stabilized Power Supply

    The circuit is designed for a max output current of 3A. The BD139 for Q2 and U2 will probably survive when the output current is 5A.
  9. audioguru2

    0-30V Stabilized Power Supply

    This thread talks about the power supply project, not your entertainment device. Please start your own thread instead of hyjacking this thread. And please type in proper English because we do not know what you are asking.
  10. audioguru2

    Battery Pack Burnout

    I have some bright chaser projects that run on two or four AA alkaline cells for months. The average current is a couple of mA and the peak current is 24mA. Some also have the connector ends of some battery holders discoloured and melted. I have a flashlight that operates from AA alkaline cells...
  11. audioguru2

    0-30V Stabilized Power Supply

    With four 2N3055 transistors at 2.5A each then the BD139 for Q2 might get too hot and die. If the BD139 doesn't die then the opamp U2 that drives it might get too hot and die. Maybe both will get too hot and die.
  12. audioguru2

    Flashing/Blinking LEDs

    A flashing LED conducts only when it flashes. If it is in series with another flashing LED then they both might have no power and will not flash. Maybe if they have a capacitor that slowly charges then causes them to flash, they both might flash at the same time.
  13. audioguru2

    0-30V Stabilized Power Supply

    Farnell is in many countries including New Zealand. Today they have a few MC34071 opamps and many TLE2141 opamps in stock. One of my suppliers is the Farnell in America called Newark. If I order before 8:00PM then it is delivered the next morning. I am in a different country (Canada)!
  14. audioguru2

    0-30V Stabilized Power Supply

    Adding a voltage regulator might destroy the regulator because its input voltage might also be too high. If the regulator survives then the max output voltage of the project will be reduced. Then you might as well use a transformer with a lower voltage. All of the improved versions of this...
  15. audioguru2

    0-30V Stabilized Power Supply

    The original circuit had many things wrong. It can't be fixed simply by changing the opamps. My first modification fixed all the problems then used very high voltage opamps that became expensive and hard to find. The latest version should be used.
  16. audioguru2

    0-30V Stabilized Power Supply

    Hi Dave, The latest version uses a choice of two common and inexpensive opamps. Their max allowed supply voltage is 44V and they work with their inputs as low as the negative supply voltage. Their outputs go down to the negative supply voltage: MC34071 opamp by Motorola, ON Semi or Freescale...
  17. audioguru2

    0-30V Stabilized Power Supply

    If you use the TL081 then you should use a low voltage transformer then the max output voltage from the project will be about 22V, not 30V. Many of the parts will still get too hot. We modified it so that the max output is 30V and it is reliable.
  18. audioguru2

    About the inverter & converter of Questions

    HHO for cars is a SCAM. Nobody has ever proved that it increases the fuel economy. It takes more power to break water into HHO than you get from it so you actually waste power with HHO. Electrolysis of water uses 2.0V at a high current, not 220V at a low current. HHO added to the intake of a...
  19. audioguru2

    0-30V Stabilized Power Supply

    A heatsink works best when the heat is spread out on it. A single point of heat on a heatsink makes that spot hot but the remainder of the heatsink is much cooler. There is a loss of cooling whenre the transistor is mounted on the heatsink. Even thermal grease blocks some of the cooling effect...
  20. audioguru2

    0-30V Stabilized Power Supply

    The very powerful transistors will work well at 5A each but you will not be able to cool them unless your heatsink is submeged in liquid nitrogen. They are spec'd to dissipate 300W when their internal temperature is max and their case is held at 25 degrees C somehow. Of course an ordinary huge...
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