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  1. Audioguru

    Use AC speakers in Car

    I looked at your photos in your post #2 and see that the amplifier IC is an obsolete TDA2822M. Your volume control is a dual so the amplifier is stereo. The maximum allowed supply voltage is 9VDC when the speakers are 8 ohms (with a higher voltage the IC will overheat) and the power before...
  2. Audioguru

    Pots!

    I think the pots are shown connected backwards so I fixed the schematic. The Mixer pot should be linear. The capacitor values should be reduced to match the increased value of the pots for the same cutoff frequencies as the original.
  3. Audioguru

    Which other transistors can I use

    The circuit is a 100MHz FM transmitter so of course a 300MHz 2N3904 transistor will work. My FM transmitter works fine with 2N3904 transistors. But the circuit is so simple that it will have problems: 1) The antenna is connected directly to the tuned LC circuit so the radio frequency will change...
  4. Audioguru

    Connecting car battery to a portable speaker.

    If your little amplified speaker has a 4.5V amplifier that produces only 0.14W into 8 ohms then that is the maximum power on the peaks of speech and music. The average continuous power is about 0.03W and its heating is about 0.1W so the battery must provide 0.13W per hour. The battery should...
  5. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    If the transformer is 28VAC then the fully loaded positive supply is +37.6V. If the current of the project is set to 3A and the output is shorted then the output transistors dissipate 3A x 37.6V= 112.8 of heat or 56.4W each. On the datasheet of a 2N3055 it says it will be at its maximum...
  6. Audioguru

    Connecting car battery to a portable speaker.

    Oh yeah? An amplifier powered from 4.5V might produce an output voltage swing of 3V peak-to-peak, which is 1.06V RMS. Then the power into an 8 ohm speaker is (1.06V squared)/8 ohms= 0.14W. Maybe the amplifier is bridged using an amplifier for each speaker wire then the voltage swing might be...
  7. Audioguru

    Connecting car battery to a portable speaker.

    A portable speaker that uses a battery that is only 4.5V has a very very low output power.
  8. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    I found the error made in a TI document. If the opamp has gain more than 1 then the output would be saturated as high as it can go. Instead of fixing the error, TI deleted the entire document!
  9. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    The experts at National Semiconductor who designed the LM339 quad comparator IC says in its datasheet that it can easily oscillate due to stray capacitance from its output to its input if hysteresis is not added. Simply using an IC socket and attaching resistors to the pins will cause...
  10. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    I did not read the Texas Instruments document you posted but I have seen some serious errors in one of their documents.
  11. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    The fan control uses one of the opamps in the LM358 as a comparator. Comparators always use some hysteresis to avoid oscillation near the switching threshold because the DC gain of an opamp or comparator is 200,000 times or more and at the threshold the load is turned on and draws current which...
  12. Audioguru

    LED's to use with speakers

    I bet your cooler stereo is powered from a 12V motorcycle battery. Then its output is 50 Whats which is 14 Watts RMS per channel bridged into 4 ohms. Recalculate the resistor for 14 Watts in each speaker. The brightness depends on the loudness. It is bright at full power but dimmed when turned...
  13. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    The circuit from India uses a BC548 transistor that has a maximum allowed collector current of only 100mA and is usually used with a maximum base current of 5mA. The LM358 opamp produces a maximum output of 60mA which will probably destroy the base of the transistor. Therefore a resistor between...
  14. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    EEK! Your schematic has lotsa mistakes and is as big as my neighbourhood. 1) The fan is always connected to +12V and ground so it runs all the time but turns off when the transistor turns on and short circuits the 12V power supply then the transistor releases its magic smoke. 2) The value of the...
  15. Audioguru

    Shaker Charger Guidance

    Most people use a charger IC designed to safely charge a Lithium battery to avoid an explosion and fire. Then they feed the IC with enough voltage and current to do the charging. Your shaker probably does not produce enough voltage and current.
  16. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    The cheap cost of the Banggood Hiland kit has been reduced to a clearance price. Who is "Hiland" anyway? I saw the Greek kit (Smart Kits?) about 13 years ago as a project on www.electronics-lab.com .
  17. Audioguru

    Use AC speakers in Car

    No because the transformer produces 11.9V RMS (peaks of 16.8V) , not 11.9V p-p. Also the transformer has only 2 wires without a center-tap. No because your half-wave rectifier produces a 0.9V voltage drop down to +4.95V. The actual 16.8V is reduced to 15V. You are talking about using a...
  18. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    With a 12V supply that needs a bypass capacitor at the 555 IC as mentioned in the datasheet for an LM555, the maximum output high is 10.5V and the emitter-follower transistor reduces the voltage to the fan to only 9.7V. Will the fan start running with such a low voltage? The transistor should be...
  19. Audioguru

    Use AC speakers in Car

    The little speakers were designed to be powered from 11.9VAC which produces 15VDC. Why do you want to maybe blow them up with 19V?
  20. Audioguru

    2 finger ECG circuit

    The datasheet for the INA128 says that its minimum supply is 4.5V but you have only 3.3V so no wonder it does not work.
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