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  1. Audioguru

    455 KHz tunable BFO circuit

    Each output of the 74HC14 outputs that are shorted to ground will try to draw 60mA so the 5 of then will try to draw 300mA! But the maximum allowed output current is only 25mA for each output and the power pins on the IC have a maximum allowed current of only 50mA. Simply connect the unused...
  2. Audioguru

    High current IL317 PSU

    The output voltage from the emitter-follower transistors fed from the diode will have poor voltage regulation. With a light load the voltage will be high and with a heavy load the voltage will be low. The datasheet of an LM317 shows how to add one or more PNP transistors "around" the LM317 so...
  3. Audioguru

    100w LED - drone mounted battery powered - Help

    Look at the datasheet of an LED driver to see if it limits the current and see its range of regulated current. You must not connect LEDs in parallel unless you buy thousands of them, test them all then group them into groups so that the LEDs in a group all have the same forward voltage. That is...
  4. Audioguru

    Audio amplifier compatability...

    An electret mic draws a current of 0.5mA so with a 9V supply and a 27k resistor, the voltage feeding the mic is 9V - (27k x 0.5mA)= nothing. For a 9V supply I use 10k then the mic gets 4V and it works well. If the supply is 12V then the resistor should be (12V - 4V)/0.5mA= 16k. If the Chinese...
  5. Audioguru

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    Digikey has thousands of 74HC132 ICs in stock today from Texas instruments for $.76US each or from Toshiba for $.67US each in through hole DIP packages or all the other surface mount packages. Other suppliers also stock thousands of them.
  6. Audioguru

    100w LED - drone mounted battery powered - Help

    The ebay LEDs are Chinese and maybe the spec's are just "made up". If you cool them perfectly then they shouild survive 1A of current. Some LEDs use 9V and other LEDs use 11V. You need something like a power resistor to limit the current because if you connect one that is 9V to an 11V supply...
  7. Audioguru

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    The 330 ohm resistors in series with the LEDs limit the 74HC current to about 7.6mA in the 2V red LED. It can be reduced to 100 ohms for 22mA of current. The maximum allowed continuous current from a 74HC IC is 25mA per output but no more than 2 outputs.
  8. Audioguru

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    The 74HC132 is a high output current replacement for the CD4093 low output current IC. The CD4093 schematic shows a 5V supply but now you changed it to 9.24V to 13.2V so the 74HC132 cannot be used. What is the function of an LED? To produce light, right? Then why do the Chinese spec's about the...
  9. Audioguru

    Turn on device when car speaker signal detected

    Then why does the title of this thread ask for "signal detection"?
  10. Audioguru

    16 mm sound troubleshooting (no sound)

    It looks like many DC voltages are shown on the schematic. Did you measure your amplifier and see what is wrong?
  11. Audioguru

    100w LED - drone mounted battery powered - Help

    The buck-boost converters do not have enough details to see if they will work but their output current is much lower than your LEDs could use.
  12. Audioguru

    Modifying AGC circuit

    Without a reverse diode I think that C3 will keep charging until the AGC does not work anymore.
  13. Audioguru

    100w LED - drone mounted battery powered - Help

    An expensive LED driver will boost a low voltage or cut a high voltage.
  14. Audioguru

    16 mm sound troubleshooting (no sound)

    The schematic was upside down, backwards and dark grey. I fixed it but the numbers are hard to read.
  15. Audioguru

    100w LED - drone mounted battery powered - Help

    The 11.1V battery will be 12.6V when fully charged and be 9V when it is dead. The LEDs will be dim at 9V.
  16. Audioguru

    Modifying AGC circuit

    The AGC circuit will allow a high voltage signal to zap the ADC before it reduces the level. Because the little transistor takes time to discharge capacitor C4. Also, the base-emitter diode of the transistor will charge capacitor C3 then the AGC will fail unless a diode is added to discharge C3...
  17. Audioguru

    Turn on device when car speaker signal detected

    The circuit will conduct all the time because the speaker wires of a bridged car amplifier probably have +6V or +7V on them (a bridged amplifier has no output coupling capacitor).
  18. Audioguru

    100w LED - drone mounted battery powered - Help

    100W at 11.1V is a current of 9A!. Then the heavy little Chinese battery might last for 8.7 minutes (or only 2 minutes) and you will see the LEDs dimming as the voltage quickly runs down. Can you calculate if the heatsink will cool well enough? Will the Chinese heatsink be made of 100% aluminum...
  19. Audioguru

    Transistor Power

    The maximum dissipation of heat is 50W continuously when its case is held to 25 degrees C by something like liquid nitrogen or something. Then the chip inside the case is at its maximum allowed temperature. But if you operate the chip at its maximum allowed temperature it might fail soon or...
  20. Audioguru

    Need help building a circuit for low voltage alarm with bi color LED with flasher

    With a 5V supply, a CD4093 can drive the LED with about 3.5mA (dim) without a current-limiting resistor or with about 2mA (very dim) with a 330 ohm resistor. For 5V supplies I use a 74HC132 quad Schmitt Trigger Nand that can supply up to 25mA (very bright) if the current is limited. I do not...
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