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  1. Audioguru

    Noisy 12v circuit from 7" LCD Screen?

    Since the new amplifier works fine for 5 hours with the screen turned off but produces pulsing when the screen is turned on then the screen is causing it. Maybe it is a lack of shielded audio and video cables? Then the unshielded video signal causes interference in the nearby unshielded audio...
  2. Audioguru

    Adding Input to the Amplifier circuit!

    The 6.5" speaker is too small to be a sub-woofer. It will be an ordinary woofer. You are correct, the inputs to the woofer amplifier are pins 5 and 6 with the ground and RCA shields on pin 3.
  3. Audioguru

    Building a drone from scratch. What motors do I get?

    Cheap toy drones use a 3.7V lithium battery. The motors are small and low power then the drone is also small. If I wanted to build a drone from scratch then I would not use cheap Chinese parts with no spec's, instead I would copy a US or UK model drone and use its parts available at my local...
  4. Audioguru

    convert 110v dc to 110v Ac

    12 little 9V batteries in series make 110VDC when new and have no load. They will curl up and die if they try to driver an inverter.
  5. Audioguru

    Noisy 12v circuit from 7" LCD Screen?

    The stereo audio amplifier does not produce 40W all the time, only during the loudest parts of the sounds, when the amplifier is blasting at its maximum ratings. But if it is oscillating at a high frequency then it might be oscillating at 40W continuously. . The amplifier is class-AB then its...
  6. Audioguru

    Help with a battery / charging circuit (can i bypass the battery?)

    Maybe the charging circuit boosts the USB 5V to maybe 7V so that the battery charges to 6V or more.
  7. Audioguru

    LM358 to make FM Audio Receiver

    It is not a radio receiver. The two transistors have the input (the base of the left one) shorted to the output (the collector of the right one). I found an awful "radio" circuit that is almost the same as the one you found:
  8. Audioguru

    I have created a circuit could anyone plz tell me if this circuit is right!!?

    The opamp input has a 75 ohm resistor, not a 1k resistor. If the input has a 0.15V Schottky clamp diode then the 0.35V into the 75 ohm resistor results in a current of (0.35V - 0.15V)/75 ohms= 2.7mA. But the current must return through the power supply pins that each have a 1k resistor to ground...
  9. Audioguru

    I have created a circuit could anyone plz tell me if this circuit is right!!?

    Who is limiting the current from the 0.35V solar cell to 200uA? The current might be high enough to zap a tiny Schottky diode if there is one at the input of the opamp.
  10. Audioguru

    I have created a circuit could anyone plz tell me if this circuit is right!!?

    I believe the manufacturer who says in the datasheet that the absolute maximum input voltage must not exceed the supply voltage, they do not say less than a diode drop is OK. Maybe they have very low voltage Schottky diode clamps in there? This sentence has been edited. Why wasn't the opamp...
  11. Audioguru

    I have created a circuit could anyone plz tell me if this circuit is right!!?

    Your schematic shows an opamp with no very important power supply. The input voltage must never go outside the power supply voltages and since your opamp is not powered then the 0.35V is wrong and will damage it. If pin 7 is +15V and pin 4 is -15V then the opamp will work fine with an output of...
  12. Audioguru

    Connecting up very small, curved pins.

    Many ICs today are not made for people to solder them. Robots do it. Some ICs are soldered in an oven.
  13. Audioguru

    AMS1117-3.3 from 5VDC show 0.09vdc

    Two resistors in series from +5V to 0V will make +3.3V only when there is no load current. Load current will cause the 3.3V to drop. A 3.3V regulator keeps the +3.3V constant when the load current changes.
  14. Audioguru

    Adding Input to the Amplifier circuit!

    How will you get +27.4V and -27.4V (54.8VDC total) from a 12V car battery? Pin 5 of the 8-pins connector is the +12V output of a 12V regulator that is fed +27.4V in the normal system and the regulator will blow up if you feed +12V from a car battery to its output. There is also a -12V regulator...
  15. Audioguru

    I have created a circuit could anyone plz tell me if this circuit is right!!?

    A lousy old 741 opamp design is 48 years old and it was designed to use a 30V power supply that is +15V and -15V. Your circuit has the tiny voltage of -0.35V connected to an input that the datasheet says must never be done. Pin 7 must be a +15V supply voltage but yours is connected to ground by...
  16. Audioguru

    Help with a battery / charging circuit (can i bypass the battery?)

    It is extremely important to know details about the battery: 1) Its chemistry. A Lithium battery can explode or catch on fire if it is charged or discharged wrong. There are two different lithium battery types each with its own voltage ratings. 2) How many cell in it. Fully charge the battery...
  17. Audioguru

    Help with a battery / charging circuit (can i bypass the battery?)

    A charged battery can supply much more power than a 5V USB connection so maybe the speaker system cannot be powered from USB. You and we do not know what the battery voltage is (probably less than 5V) so shorting the 5V USB connector to the battery wire with the battery disconnected might damage...
  18. Audioguru

    Light therapy device

    If a distributor runs out of LEDs and orders more, the new ones might come from the same recent batch and will not have random forward voltage but all might be low or all might be high. Your current limiting must allow for this.
  19. Audioguru

    Charging Led Circuit

    I replaced the worn out Ni-Cad battery in my hand-vac with some Li-Ion cells from a laptop computer. It doesn't need LEDs. I tried it a moment ago because it hasn't been used or charged for a few months. 1) It runs but not at its maximum speed. 2) After charging overnight it will run at full...
  20. Audioguru

    Light therapy device

    The IR power produced by the LEDs is simply determined by their actual forward voltage (that your wizard wrongly assumed is the typical voltage), the supply voltage, the number of LEDs in series and the resistor value. 4-pins LEDs are made for visible lighting and probably are not made to...
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