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  1. Externet

    1W audio power amplifier driven by electret ?

    Hi, thanks. The input sound is plain conversation level voice picked at a fixed 3cm from lips side by an electret, preamplified and fed to probably a LM4871 or similar to a tiny 50mm 4Ω speaker with no acoustic feedback path towards the mic. A manual or remotely controlled volume control is...
  2. Externet

    1W audio power amplifier driven by electret ?

    Thanks. I will then add a preamplifier section if any extraordinary chip does not surface. No volume control to be implemented, will have fixed high gain.
  3. Externet

    1W audio power amplifier driven by electret ?

    Thanks. No problem on adding a discrete circuit to give the needed gain to an electret and feed an amplifier IC; but with so many new products on the market I wanted to make sure there is not a chip with everything included. Am restricted in size to 19mm diametre round PC boards that I can stack...
  4. Externet

    1W audio power amplifier driven by electret ?

    Thanks. That is the old stuff; now it is surprising to see dozens of audio amplifiers on the market, class D and boosted. Even with DSP processor built in 4mm x 4mm. I am learning to discern among them. The feedback howling is of no concern. Here is one of maaaany : ---->...
  5. Externet

    Need to reduce 5V 500ma to 3V 30ma

    As above, 3 diodes 1N4001 in series : +5V-------------|>|----------|>|----------|>|-------------+3V
  6. Externet

    1W audio power amplifier driven by electret ?

    Is there such thing among the multitude of tiny ICs new in the market ? Am after finding, ideally : Integrated circuit, Analog amplifier , any class, BTL or not, For a 3 to 4 V DC supply, 1W or near that power output, For electret microphone input, or conventional 8Ω cone speaker as microphone...
  7. Externet

    LED's to use with speakers

    Made this, has been working for years...
  8. Externet

    ID Potentiometer

    Come on !. Use your ohm meter !
  9. Externet

    What vibration sensor for bearing monitoring

    Sorry, by some mental fart linked the first wrongly... ----> https://duckduckgo.com/?q=knock+sensor&t=canonical&iax=images&ia=images
  10. Externet

    Amplifying piezo buzzer

    Is it energized/powered with DC or AC in your circuit ? - What is the voltage when emits some sound ?
  11. Externet

    What vibration sensor for bearing monitoring

    Use any automotive knock sensor, which is nothing else than a sturdier-mounted microphone and available as car parts. ----> https://duckduckgo.com/?q=knock+sensor&t=canonical&ia=web ----> http://www.denlorstools.com/home/dt1/multilist_103/automotive_noise_detection_tools_and_sound_meter.html...
  12. Externet

    Amplifying piezo buzzer

    There is two different things. A piezo buzzer which contains an oscillator, usually magnetic actuator and DC driven, and a piezo disc element, which needs a much higher AC voltage to be loud. Which is it you are working with ? ---->...
  13. Externet

    Popping sound when switching microphone with relay

    Or try two of the three sections of a CD4053 integrated circuit instead of the relay. But use a 12VDC supply instead of 24VDC.
  14. Externet

    Tractor fuel sender not working

    It is normal to pay a price for guessing instead of diagnosing.
  15. Externet

    2 led

    Insert a resistor in series with the 5V supply and will dim. Try 100Ω, or 330Ω, or 470Ω to taste. A 1KΩ potentiometer instead, can adjust the brightness.
  16. Externet

    Tractor fuel sender not working

    Probe for +12V at the 'sender' supply wire turning the ignition key 'on'
  17. Externet

    Solar charging module for LiFePO4 batteries

    Why using a module ? What is the voltage generated by the 'small' panel ? If between 4 and 6 volts, connect the lithium cell directly. If more than 6V, a series diode(s) will step the panel voltage down. If more than one lithium cell in series, use a 'small' panel (4-6V) for each cell.
  18. Externet

    Mysterious vacuum tube

    Read under the base; ----> http://www.geocities.jp/radiomann/HomePageVT/Radio_tube_13A.html
  19. Externet

    Current Operated Relay

    The Sunbeam 9W led bulbs I have in the house are labeled 135mA 125VAC, available for $1 at the 'Dollar tree" store. And yes, can be paralleled. Will see your schematic..."
  20. Externet

    Current Operated Relay

    110VAC-------------/\/\/\/----------LED---------relaycoil----------load-----------neutral Is this what you meant ? For a LED capable of conducting 200-400mA ?
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