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  1. Audioguru

    Turn off ALL power to LED

    Please post your schematic so we can see where the magic power is coming from. The magic power is probably coming from the solar panel. My LED solar garden lights produce light in the daytime when the battery is removed. The QX5252 produces DC pulses, not AC. The diode and capacitor smooth the...
  2. Audioguru

    Ultrasonic pest control

    One test showed that an ultrasonic pest repeller attracted pests when it was turned on. Other ultrasonic pest repellers produced no ultrasonics.
  3. Audioguru

    Ultrasonic pest control

    Ultrasonic repellers are an excellent way for the manufacturer to make lots of profit from gullible people who buy them. The repeller's ability to repel pests works the same if it is turned on or is turned off.
  4. Audioguru

    The mobile power bulges

    Tip? I looked in Google and it said what I guessed, British for "a place where trash is deposited". Some people over there put a swollen battery in the boot of a caw. They do not put it in salt wotah.
  5. Audioguru

    Which speakers are best for home?

    In this age of people working from home to avoid getting the virus at work, TV news has experts talking from their homes that are frequently full of resonance and echoes. Of course the resonance and echoes are made much worse because they hid the microphone too far away from their mouth. I can...
  6. Audioguru

    A Little Delayed in Starting

    The decoupling capacitors are supposed to be connected as close as possible to pin 1 and to pins 3 and 4. Then their sequence does not matter.
  7. Audioguru

    How long will a 0.9ma nano motor unit last on a DCell?

    The specs for the motor says it draws 80mA from 1.5V. The specs say the motor runs when it gets 1.5V to 3V. Then maybe it stops in a week when the battery voltage drops to 1.4V?
  8. Audioguru

    How long will a 0.9ma nano motor unit last on a DCell?

    Since nobody uses D cells anymore then if you find one it might be an old one with very poor quality (Super Heavy Duty garbage carbon-zinc) at The Dollar Store or it might be a Name-Brand alkaline D cell with a little C cell inside. Even a Name-Brand D cell might have been running down in a...
  9. Audioguru

    How to choose this PNP transistor

    Attach the schematic as a "Thumbnail" so we can click on it which enlarges it. Here is what I see:
  10. Audioguru

    Is there a device to hookup to cellphone charger

    The sales person is wrong. All Lithium-Ion battery chargers detect a full charge then turn off the charging to avoid an explosion and/or fire, and let the battery last a long time.
  11. Audioguru

    Just When I Thought it was Going to Be Easy

    It is a shame that Amazon and their sellers know nothing about and post wrong photos about the electronic parts they sell.
  12. Audioguru

    Just When I Thought it was Going to Be Easy

    I guess you need a multimeter to show DC polarity and AC and DC voltages. It also measures resistance and a diode voltage drop.
  13. Audioguru

    Just When I Thought it was Going to Be Easy

    If you used a new Name Brand 9V battery and its polarity was backwards then the IC is probably destroyed. But if you used a no-name-brand "Super Heavy Duty" battery from China then it probably did not have enough power to do damage.
  14. Audioguru

    Best op-amp for audio use?

    I cannot hear the second harmonic of 12kHz or the third harmonic of 8kHz then I probably would not try making an audio circuit with the 55MHz (!) LM4562 because it would probably oscillate. It costs almost $3.00 US. The LM4562 has a rated distortion of only 0.00003% when its gain is 1 like a...
  15. Audioguru

    Best op-amp for audio use?

    The TL071, TL072 and TL074 are very old (I used thousands of them many years ago) and newer ones have much less noise. The newer OPA134, OPA2134 and OPA4134 are excellent and work from a supply range of 5V to 36V.
  16. Audioguru

    Will this charger work?

    There are no details of the charging and discharging. Charging at its 20A and discharging at 40A will explode many Lithium batteries. The ad does not say if they are programmable.
  17. Audioguru

    Will this charger work?

    Maybe you have a protection circuit which is not a charger circuit.
  18. Audioguru

    Is this possible to do?

    Of course the 4-wires LED can produce different colors at different times because it has 3 LEDs (red, green and blue) inside. You can even activate 2 or 3 colors at the same time to make many more colors. You can connect the activating circuit to your "Magic jack" but not to an ordinary phone...
  19. Audioguru

    Speaker/s project - for amplifier.

    Why do you want 16 ohms? Most speakers today are 8 ohms and cars use 4 or 2 ohms for lots of power when the amplifier is powered from 13V. I looked at the specs of 10" "Eminence" guitar speakers. They are only 8 ohms. They have the same "awful" frequency response as other guitar speakers and as...
  20. Audioguru

    Adding pre out on soundbar for sub.

    Some cheap soundbars use little Shriekers instead of speakers. No bass.
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