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  1. audioguru2

    High Power LED Mood Lamp

    Hi Gramo, I started this thread because the value of the base resistors is too high to allow the transistors to conduct the high currents needed for the expensive tri-colour LED. I also noticed that the value of the current-limiting resistor for the red LED was too low and would cause the...
  2. audioguru2

    LM338/LM318 Not enough power. Vref drops!

    You had 10W of dissapation. The thermal resistance from the chip to the air is 35 degrees C/W so the chip was at 350 degrees C above the ambient temperature of 25 degrees C. The thermal resistance from the chip to the case is 1 degree C/W so the case would reach 340 degrees C above the ambient...
  3. audioguru2

    LM338/LM318 Not enough power. Vref drops!

    We don't know how much time it takes for 375 degrees C on the chip inside the IC to heat up its case. Its case can be at room temperature and its insides could be too hot. The datasheet for the LM338 shows it limiting its output current from 12.5A to 8A within 10ms when it has a good heatsink...
  4. audioguru2

    What are the connectors?

    Connect the polarity of the terminals on the jack to match the polarity of the plug on the mains AC to DC adapter it will be used with.
  5. audioguru2

    What are the connectors?

    You can make the center pin positive or negative depending on what you connect it to. The barrel is the long barrel of the plug. It is the metal frame and nut of the jack. "The other one" is a switched contact that connects to the barrel when there is no plug and the plug disconnects it.
  6. audioguru2

    Audio Preamplifier Design Project

    Kevin, Noise in the audio band is an audio signal. All audio amplifiers will pass it. If you filter out all noise then you filter out all audio. The same applies to video signals. If the noise is a low frequency rumbling noise then filter out all the bass frequencies. If the noise is a high...
  7. audioguru2

    What are the connectors?

    It is easy to see which terminal connects to the center pin. It is not too difficult to see which terminal connects to the barrel. Then the remaining terminal is switched. Double check its terminals with an ohm-meter.
  8. audioguru2

    LM338/LM318 Not enough power. Vref drops!

    No heatsink??? It has 10.5V-3.0V= 7.5V across it. It has 1.33A through it. Therefore it is dissipating 7.5V x 1.33A=10W. Its max allowed internal temperature is 125 degrees C. Its TO-3 package has an internal temperature rise of 35 degrees C/W without a heatsink. Boy is it ever hot at about...
  9. audioguru2

    High Power LED Mood Lamp

    Why was Gramo's reply deleted? It was important.
  10. audioguru2

    LM338/LM318 Not enough power. Vref drops!

    Hi Oscar, Welcome to our forum. ;D I think either the LM338 is getting too hot and is shutting down or it is defective. They typically can supply 9A if they have only 5V across them and are cooled properly. Maybe your servo is stalled and draws much more than 5A.
  11. audioguru2

    speed shift according to music.

    How can I help you? You forgot to say the voltage and current requirements for your electric motor. An electric motor could be a tiny one that vibrates a cell phone, operates from only 1.5V and uses only 20mA of current. Or an electric motor could be a 270V big one in a hybrid gasoline/electric...
  12. audioguru2

    500W sine wave inverter design

    A tiny Seat (a Fiat made in Spain?) Ibiza is a little scooter with 4 wheels, isn't it? 3 wheels? A little 35Ah battery is for an electric toothbrush, isn't it? ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D ;D ;D  ;D...
  13. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    This simple inverter has a square-wave output. Many electronic devices need a sine-wave because they charge their power supply capacitor to the much higher peak voltage of the sine-wave. Some transformers overheat when driven with a square-wave.
  14. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    A 12VA transformer has a power of only 12W. A 30VA transformer has a power of only 30W. What do you have that uses such a small amount of power from the mains? Stores sell a tiny cheap inverter with an output of 75W. I don't know what it is used to power.
  15. audioguru2

    A sleep Timer

    The emitter-base of the PNP transistor is a forward-biased diode from the positive supply to the collector of the NPN transistor. I think so. It might keep Q1 turned off when the circuit is first powered. The "gate" supplies power to the IC because Q2 is an emitter-follower and its base and...
  16. audioguru2

    12 V DC to a 220V AC Inverter AMplfier Design

    The transformer has a center-tap that is connected to the battery. The winding has a 12V terminal that connects to Mosfets on one side and another 12V terminal that connects to Mosfets on the other side. If the inverter is for 500W and has 100W of heating then the Mosfets on each side conduct a...
  17. audioguru2

    MNA question about amplifier

    The LM380 has a voltage gain of 50, so the max output from the Mosfet is only 180mV p-p. Then the supply for the Mosfet doesn't need to be 24V and the negative supply is not needed. The Mosfet operates on an extremely low current. Its drain resistor's value is so high that it is loaded down by...
  18. audioguru2

    speed shift according to music.

    An engine? What powers it? Gasoline? In a car? It is easy to make an electronic circuit that has an electrical output when there are bass sounds. Then the electrical output can drive a solenoid that pulls on the engine's throttle to make it speed up for a moment. At a stoplight?? Behind a big...
  19. audioguru2

    Fridge door alarm circuit

    If you use brand new alkaline battery cells then the supply voltage is only 3.0V and the beeper gets only about 2.2V from the emitter-follower transistor. A beeper barely works with only 2.2V. Use a 6V, 9V or a 12V battery and it will be much louder.
  20. audioguru2

    High Power LED Mood Lamp

    That is gambling. The datasheet for the PIC is very clear: Do not use an output current of 25mA or more.
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