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  1. audioguru2

    3V LED Chaser project

    Hi Ibernez, Welcome to our forum. I have been making lots of these chasers. I have made some with Ultra-Bright LEDs, and they are really bright, probably more suitable for your guitar project. The Ultra-Bright LEDs need more than 3V so I modified the circuit a bit and use 4 AA alkaline battery...
  2. audioguru2

    Choosing terminals for step down transformer

    Only 24V?
  3. audioguru2

    Electronic Stethoscope 2

    Hi Hakyman, You have many questions, let's see if I can answer them. 1) C7 supplies positive supply current when the positive battery runs down and its internal resistance rises. The LM386 power amp draws a fairly high current during heartbeats and you don't want the supply voltage to fluctuate...
  4. audioguru2

    Negative charge pump

    Then you have reduced the opamp's output voltage swing from 1V to 4V to only 1.7V to 3.3V.
  5. audioguru2

    Dome Lamp Dimmer

    Hi Alun, I see how Pulse Position Modulation changes the pulse width somewhat, but I don't think that a pulse width range from 10% to 70% is enough to dim a lightbulb. It is more suitable for motor speed control.
  6. audioguru2

    Negative charge pump

    Hi Kevin, Which opamps are you using to provide such a high output current? Their outputs certainly won't swing from 0V to 5V unless they are rail-to-rail types and are driving a low-current load. You are losing a B-E voltage drop on emitter-follower transistor T1, and maybe more voltage...
  7. audioguru2

    Maximum current for AC/DC adaptors

    Hi Alun, My little adapter showed its ripple voltage charging quickly, then decaying slowly into the load, as I expected. My big adapter showed nearly the same charge and discharge times, like a triangle wave, maybe because its secondary resistance is too high. Sorry I can't measure more...
  8. audioguru2

    Dome Lamp Dimmer

    Hi Alun, Your Pulse Position circuit basically changes only the frequency of the oscillator. With your 10:1 timing resistor values, its duty-cycle will remain about 50:50 for most of its range so the lightbulb will always be at half brightness. Try a 555 this way, make the timing resistors...
  9. audioguru2

    Maximum current for AC/DC adaptors

    Hi Alun, I have never seen an AC to DC wall-wart adapter produce such a high amount of ripple. I just measured two 120VAC/9VDC adapters: Rating 9V, 200mA 9V, 500mA Primary DC resistance: 634 146 DC...
  10. audioguru2

    Electronic Stethoscope 2

    Hi Hakyman, I am glad to hear that your Electronic Stethoscope-2 project really works good. 1) It is too bad that your broken Sony earphone makes a "pit-pat" sound that your language alphabet or fonts can't reproduce. 2) Pin #1 on a TL072 is "the output of its opamp #1". 3) I recommended...
  11. audioguru2

    Dome Lamp Dimmer

    Hi Ameya, Welcome to our forum. Our Dome Lamp Dimmer project uses a standard Pulse Width Modulation circuit. The schematic is missing a wire:
  12. audioguru2

    heavy duty batteries

    Many people also buy cheap "alkaline" batteries that are made in a country that they never heard of. Who knows what is inside those batteries or how old they are? My Energizer alkaline battery cells that I got cheaply at an after Christmas sale are USA-made and are stamped with a "best-before"...
  13. audioguru2

    Electronic Stethoscope 2

    Hi Hakyman, Happy New Year. 1) Did you build the Electronic Stethoscope-2 project or the original project? 2) What is a " pıt" sound? 3) What is a " 4ohm 5W hop"? The LM386 is not designed to drive a load impedance less than 8 ohms, it may be damaged by excessive output current or...
  14. audioguru2

    Audio signal generator

    Hi Travis, My "ringing bandpass filter" idea is a bandpass filter like used in a sine-wave oscillator but its gain is set to just below the amount necessary to sustain oscillation. Its frequency is set with 2 resistors that can be switched or controlled with a dual pot like a stereo volume...
  15. audioguru2

    Audio signal generator

    Hi Travis, Welcome to our forum. You probably need a bandpass filter circuit that has its gain set just below feedback. Your kick pedal switch would send it a DC pulse and it will ring at its set frequency and slowly decay away, just like a real drum. You could even have pushbuttons or a knob to...
  16. audioguru2

    electronic experment sites

    If 12 for 12 can't speak "geek", maybe he means that he can't read schematics. ;D
  17. audioguru2

    wireless transmitter

    Hi Tazmania Kid, If you change the frequency of a simple FM broadcast band transmitter to 475-500MHz, its "general purpose" transistors must be changed to high-frequency types. Hi Alun, Thanks for posting and describing your 4 transistor FM transmitter. It would probably need only 3 transistors...
  18. audioguru2

    Temperature:Speed Timer Circuit?

    Hi Twizted, Your thermal probe has an enormous range to change its value from 50K when freezing to only 3K at body temperature. You just need to know its resistance at the temps that you are going to use it. Try your circuit with the thermistor in series with a 1K resistor replacing the 47K...
  19. audioguru2

    Temperature:Speed Timer Circuit?

    Hi Ante, I've never used a glass bead thermistor, just diodes and light bulbs. I walked all over my computer salesman when I got my "price match" refund. He didn't think his low price could be beat by so much! I still have many mail-in rebate coupons to send. When the rebate cheques arrive and...
  20. audioguru2

    Site's Clock

    Hi Guys, The site's clock is still about 19 minutes fast but also has another problem. On the "home" page, the "recent topics" shows posts with the server's clock, not my programmed time-zone shifted clock.
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