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  1. audioguru2

    Flasher?

    Sure, Hearse, I'll post the drawing after I learn Cadsoft's Eagle.
  2. audioguru2

    Two-way Crossover, Audio Project

    Man! That translation gave me a hard time. The project is here: http://electronics-lab.com/projects/audio/002/index.html If wired as shown, then this project produces a notch filter at the crossover frequency. Due to phase shifts of 2nd order filters that are used, sounds at or near the...
  3. audioguru2

    Batteries Charger & PSU - for Cameras

    Ante, thanks for your correction. Although the 7805 can be a current regulator, do you see that it can't be used here, since it would need at least 7V across it (plus the 6.3V or more for the batteries)?. The transformer voltage is too low for that. If the transformer voltage was increased then...
  4. audioguru2

    Batteries Charger & PSU - for Cameras

    Hi Guys, I was wondering, how can this project charge four NI-MH batteries from only 5V in series with a diode, and how can a resistor in series with a voltage source supply "constant current"? The AA size NI-MH batteries that I have charging right now at 150mA, which is less than their...
  5. audioguru2

    LED Flasher (very Interesting.............)

    Thanks, MP: Those circuits WILL light 6 LEDs in a Knightrider fashion. They use diodes as OR-gates, so that 4017's outputs #1 to #6 light LEDs #1 to #6 in sequence, then output #7 lights LED #5, output #8 lights LED #4, etc. and back down to LED #1, then it starts over again. A brilliant use of...
  6. audioguru2

    Flasher?

    MP, Thank-you very much. I will use this software to post my many tried and proven projects.
  7. audioguru2

    LED Flasher (very Interesting.............)

    Hi again, An analog circuit will make an LED Knightrider circuit: 1) A classic 2-opamp ramp generator (1st stage is a comparator with hysteresis and the 2nd stage is an integrator and the stages connect together with feedback). 2) The ramp generator feeds an LM3914 voltage-to-dot driver driving...
  8. audioguru2

    Who is using the oldest computer?

    Hey guys! When I say USING it, I mean it! My 486 is used every day on the internet (cable) for surfing, e-mail, ordering parts and for word-processing invoices, etc. It is reliably running Windows 98, 1st Edition and very rarely crashes. It is all-in-one, like a Mac, so I can't even put a good...
  9. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Mastrila, Can you scope the Variac's output to measure the peak-to-peak output with and without a load? A meter can't measure p-p. Does the output of the power supply have hum when it is loaded?
  10. audioguru2

    Flasher?

    Hearse, Are you the same guy that was on another post-board requesting that the LEDs flash about 5 times on the left LED then 5 times on the right one, and back and forth like that? This circuit will do that with only 2 CMOS gate chips (4001B or 4011B, or 1 of each): 1) A 2-gate Classic CMOS...
  11. audioguru2

    LED Flasher (very Interesting.............)

    Hi guys, The Chaser circuit will not make the LEDs go back and forth like YOURWINS cool animation of a Knightrider. Instead the LEDs will start with #1, then #2...... up to #10, but the next LED will be #1, then #2 etc. The reason is that the 4017 can only count up, not down. That is why the...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Ian, welcome to Electronics-Lab and to the hobby. 1) Connect the positive terminal of a 3A DC ammeter to the positive output of the circuit. 2) Connect the positive terminal of a 30V DC voltmeter to the negative terminal of the ammeter. This junction becomes the positive connection of the...
  13. audioguru2

    Electronic Stethoscope

    Hi, MP, thanks for your anaysis of the original circuit and your comments on my recommended fixes. But I am sorry to have additional corrections for you: 1) U2 can easily drive the 2.5K volume control. The 741 is spec'd with a minimum load of 2K. The 2.5K load on U2 will not affect its gain nor...
  14. audioguru2

    Timezone

    I hope that this hasn't been posted before, the Search didn't work this time. The "date and time posted" shows as GMT timezone. Since I am in the Eastern North American timezone then it shows postings sometimes tomorrow and is very confusing. Does this board have a preference-entry for me to let...
  15. audioguru2

    Who is using the oldest computer?

    Hi Guys, Many people say that I should upgrade my computer. But even though it is nearly 10 years old, it does almost everything that I need. It has been downloading reliably for years from the internet at 350KB/s to 1MB/s (thats bytes, not bits like a 56Kb modem) on cable (they say it is...
  16. audioguru2

    Lasersound

    Siddhu and Hotwaterwizard, I found (isn't Google great?) the link about "hypersonic sound" and their use an array of many ultrasonic transducers to create a plane (flat front not curved) wave that travels through the air without spreading-out. Another benefit of this system is that if you are in...
  17. audioguru2

    +- 15vdc Dual Converter

    Hotwaterwizard, TR1 and TR2 won't switch anything, with D4 and D8 connected backwards. Where is the positive supply for TR1 and the negative supply for TR2 going to come from? Also in your oscillator, when one transistor conducts, it drives the base of the other transistor negative, through the...
  18. audioguru2

    Electronic Stethoscope

    MP, In the schematic, U2 and U5 are shown without negative feedback. Therefore, DC-wise, their outputs would be idling against a power rail since their enormous gain would amplify their offset voltage. AC-wise, any tiny signal (or noise) that is greater than their offset voltage (only a few...
  19. audioguru2

    Electronic Stethoscope

    Cdak, MP's expander circuit is a good idea. But your scope picture seems to show a continuous low-frequency. Are you using shielded cable from your mic to avoid hum pick-up, and insulating the mic and its cable from the patient to avoid a ground loop?
  20. audioguru2

    Electronic Stethoscope

    MP, Well, let's see: Electronics-lab posted an audio circuit which has 2 op-amps running open loop without any feedback, an input capacitor which can be calculated to severely cut the desired sound, an output stage without proper bias and many complaints that it doesn't work. The author of the...
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