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  1. Audioguru

    Connecting led fairy lights together powered by ac mains

    White and blue LEDs are about 3V. Then 20 in series need 80V that you do not have. I believe that the LEDs are matched and are in parallel, not in series. 20 LEDs in parallel will use a current of maybe 100mA to 400mA. The current is probably limited by the very cheap battery cells used. Then...
  2. Audioguru

    Specific IC s used in solar circuit

    My older cheap Chinese solar garden lights used an LDR that got corroded and failed within one year. The next year the newer solar garden lights used the solar panel to sense light but it had a plastic cover that got sunburned within one year and its Ni-Cad battery cell rusted away in a couple...
  3. Audioguru

    220v speaker problems

    A modern solid state amplifier has an output impedance that is very low, 0.04 ohms or less so that it can damp the resonances of a speaker. It has a maximum allowed output current that determines the lowest allowed impedance of a speaker. Old vacuum tube amplifiers had an output transformer that...
  4. Audioguru

    Portable speaker problems. ( First Post )

    If the speaker impedance is 8 ohms and the amplifier has one output wire and one ground wire then the power when the output is barely clipping is about 1W. If the speaker is 4 ohms and the amplifier is bridged with two output wires then the output power is about 7W. If the speaker is 2 ohms and...
  5. Audioguru

    buck converter/step-down converter vs resistor vs linear regulator. Whats the different?

    A buck converter oscillates its output on and off and the filtering is poor so it cannot be used for audio or video. A resistor does not produce a regulated voltage, instead it limits the current. since the current is limited then the voltage is reduced but is not regulated. If the load current...
  6. Audioguru

    9v Guitar Amp w/out LM386

    Your transistors appear to be small and might not conduct the high current needed or they might overheat. Please post the schematic showing resistor values and transistor part numbers.
  7. Audioguru

    LED's in a geodesic array

    200W is a lot of heat for a "small dome". A heatsink must have a high surface area which will not be available. Maybe the dome should be in a bucket of liquid nitrogen? 45 LEDs in series at 3.2V each need at least 144V which is not available from a 12V computer power supply. Most LED dimmers...
  8. Audioguru

    Portable speaker problems. ( First Post )

    12V at 1.5A is 18W. The amplifiers might be class-AB with 55% efficiency then the maximum output power is 9.9W or the amplifiers might be class-D with 90% efficiency then the maximum output power is 16.2W. Amplifiers are never always at full blast, their average power is about 1/10th so the...
  9. Audioguru

    9v Guitar Amp w/out LM386

    Don't electric guitars need the severe distortion caused by crossover distortion? The speaker might rectify audio if the output coupling capacitor is removed since the DC will force speaker cone one way either in or out then it cannot swing normally in and out. Another way to increase the...
  10. Audioguru

    9v Guitar Amp w/out LM386

    A simple circuit is the same when it is copied. Its sound and performance are awful. But some people like a guitar amp to sound awful and have terrible performance. I was wrong about the peak voltage. The peak current is half of 675mA which is 338mA and the peak driver transistor current is...
  11. Audioguru

    Circuit validation & improvement

    Your huge RC airplane draws more battery power than an All Terrain Vehicle! Look at their speed control circuit to see how many paralleled output transistors are used.
  12. Audioguru

    12 v to 48 v boost converter for 48 v electric bike

    Pulse-Width-Modulation is efficient because the output transistors switch on and off quickly and do not waste a lot of power making heat. A class-D amplifier uses PWM but here a transformer can stepup the voltage.
  13. Audioguru

    Portable speaker problems. ( First Post )

    Do you know that an 18650 cell is Lithium that is very dangerous? It is destroyed and might explode if you try to charge one that had its voltage drop below 3.0V so you must have a circuit to measure the battery voltage and disconnect it when its voltage drops below 3.0V per cell. The charger...
  14. Audioguru

    9v Guitar Amp w/out LM386

    Most speakers are 8 ohms. The most important spec for a power amplifier is, um, maybe its output power?? The amount of output power at clipping tells you the power supply voltage that is needed. You mentioned an LM386 that produces 0.45W at clipping into an 8 ohm speaker when the battery is...
  15. Audioguru

    LED headlight build

    An LED is not an accurate length of tungsten wire as in a light bulb, instead it is a special diode that has a range of forward voltage. The datasheet should say its minimum which might be 6V and say its maximum which might be 8V, then you can calculate the resistor value when the LED is 6V and...
  16. Audioguru

    FM Antenna Connection

    The electric plug should NOT connected to the circuit ground.
  17. Audioguru

    Circuit validation & improvement

    The datasheet fore the MJ11028 darlington shows that its maximum saturation voltage loss is 3.5V at 50A and at 80A it is much higher. At 80A it might be 5.4V max which is a dissipation of 80A x 5.4V= 432W which will destroy it even with a perfect heatsink. Use two or more darlingtons in parallel...
  18. Audioguru

    Over discharge problem

    The battery and voltage booster you show might not protect the battery from discharging too low.
  19. Audioguru

    Circuit validation & improvement

    I think it is the battery and its wiring that heats with nearly 800W, not the power transistor. He said that at full power the battery loses terminal voltage therefore he added battery cells in series to make up for the loss. The voltage regulation is used to reduce the maximum battery voltage...
  20. Audioguru

    Over discharge problem

    A Li-Po is a Lithium ion battery. An 18650 Lithium battery cell might have a protection circuit inside that disconnects it to prevent it from being destroyed by over-discharging. A Li-Po battery does not have a protections circuit, it relies on its load having it. My RC airplanes all have a...
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