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  1. audioguru2

    How to build powerful neutral or earthing

    Your soil is too dry for your small grounding rod. Try a rod a few hundred feet long. If it strikes oil, you'll be rich. If it strikes water then your lights might be bright. If it strikes gold you'll have both! ;D In my country, electricity is distributed to me with a neutral wire. My...
  2. audioguru2

    Time out circuit

    Hi Prateek, For a 15 minute time period, the capacitor's value and its leakage current will be huge. Maybe you could use forty-five 20M resistors in series and a 1uF low-leakage poly cap. Or one 20M resistor charging forty-five 1uF poly caps in parallel, driving a Mosfet. It is the same problem...
  3. audioguru2

    LIGHTENING STRIKES

    www.howstuffworks.com  ;D ;D
  4. audioguru2

    car battery charger

    Hi Ante, Yeah, I've had a lead-acid battery that was sitting for some time completely discharged, and it took a long time for it to begin charging normally. I think it became "sulphated". I have also left my car's lights on after a morning drive to work in the dark and getting there at dawn when...
  5. audioguru2

    Back To School!

    Hi Tkr, Your Associates degree won't be wasted by getting an Engineering degree at university. You will have fun teaching the teachers like I did! ;D ;D But go easy on them in the beginning. 8)
  6. audioguru2

    car battery charger

    Hi Ante, I am amazed that it is so simple. If you try to charge a completely flat battery doesn't the fuse blow or the electrolyte boil? I was told that a flat battery puts a huge strain on a 50A(?) ordinary alternator.
  7. audioguru2

    Motorola Hi-Fi power amplifier

    Hi Ante, It is a simple way to reduce the supply voltage of the opamp and still allow the output transistors to have their full supply voltage swing. ;D
  8. audioguru2

    Motorola Hi-Fi power amplifier

    Hi Alun, We have a 200W amp in our projects section that does the same thing. Except it uses a 10W wideband power amp IC instead of a lousy 741 opamp. http://www.electronics-lab.com/projects/audio/013/index.html When the output of the opamp goes positive, it drives a massive (!) current into...
  9. audioguru2

    Common LED as IR Detector

    Hi Abu, Someone talked about this before, but I couldn't find it with a site search. Maybe the discussion was on another site. I tried shining a red Led onto another red Led. When they were touching, the receiving LED produced a voltage output with hardly any current. With a couple of cm...
  10. audioguru2

    car battery charger

    Hi Platonas, Thanks for the good explanation. The circuit will certainly turn itself off when rhe battery is fully-charged, and even turn itself on when the battery voltage sags due to self discharge. ;D
  11. audioguru2

    car battery charger

    Hi Sasi, I like your Ni-MH battery charger circuit, except: 1) The old LM301 hasn't been produced for 10 years. 2) The old LM301 doesn't work well with a supply less than 10V. I would use a modern TLC081 instead. It works well with a 4.5V to 16V supply. ;D
  12. audioguru2

    car battery charger

    Hi Born, Are you joking? If a 4000W inverter is 80% efficient, it would draw 5000W from the 12V battery at full output. That's a current of 417A! If a car battery doesn't explode or boil, it would last about 22 minutes. Connecting wires and for the primary winding of the transformer about the...
  13. audioguru2

    car battery charger

    He, he, he, he. [move] ;D ;D ;D
  14. audioguru2

    car battery charger

    An ordinary transistor turns on and off pretty well too. ;D Instead, he used a 500V(!) SCR. I checked, its minimum holding current is only 7mA. So you would need to disconnect the battery to turn it off. He says it works fine. My car battery has unlimited charging current and continuous...
  15. audioguru2

    car battery charger

    I think Q1 will never turn off and a high trickle current will be maintained. I have never seen an SCR that stops conducting when its gate voltage is removed like a transistor. The circuit is basically only the fuse in series with a diode (the conducting SCR) that is charging the battery. Plus...
  16. audioguru2

    Sub for TL071

    Hi Rhonn, Ed's post shows that low resistance and capacitive compensation in the divider is important for wide bandwidth. Your 1M resistive dividers plus the input capacitance of the opamps and protection diodes will rolloff frequencies above only about 1kHz without having a compensation cap...
  17. audioguru2

    Sub for TL071

    Sure, your application is perfect for it. Low-capacitance shielded cable, a ballpoint pen casing and a stiff pointed end is all you need. I use tiny alligator clips on the end of low-cap cable for my old 5MHz 'scope. Are you going to look at the 240VAC output of inverters? ;D
  18. audioguru2

    car battery charger

    Hi Sasi, I like your charger. ;D It is good (gud?) that you included a float-current adjustment. Your charger must be pumping many Amps into a battery that is completely discharged. I was thinking about using a similar charger for quick-charging a Ni-MH battery. If it is set to 1.4V to 1.5V...
  19. audioguru2

    Sub for TL071

    Hi Rhonn, You're making an AC voltmeter with a gain of only 10, so I don't think you would notice the noise from a "regular" opamp such as a TL081. The circuit needs a FET input opamp like the TL071 and TL081 because of the circuit's high resistor values at its input divider. The 100kHz...
  20. audioguru2

    Motorola Hi-Fi power amplifier

    Hi Miles, I wouldn't put an ammeter on a very low output impedance amplifier if its offset voltage wasn't zero. The only current limiter is the fuse. (the fuse in your meter);D Years and years ago when audio amps started using opamps in them, the designers demonstrated extremely low distortion...
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