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  1. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    Ante, It always starts with me making a suggestion to make a faulty circuit better. Here I wanted the first "helper" to join me in a discussion about improvements. Is he miserable because I replied to him and made further recommendations along with his? Then I am wrongly told that my fix is...
  2. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    Would any other members like to join this discussion about opamp biasing?
  3. audioguru2

    Diana needs help about NCS2001 amp

    Diana, ON Semi also make small power amplifier ICs for headphones. Although they make one for mono sound, I recommend using the stereo IC since it is the same size and uses the same number of external parts. Besides, you will probably want stereo in the future. You have a choice of 2 ICs, the A...
  4. audioguru2

    0h help. I need help with FM telephone bug!!!

    Grigspace, It's in our projects section, and also here: http://www.electronics-lab.com/projects/telephone/007/index.html
  5. audioguru2

    0h help. I need help with FM telephone bug!!!

    Kecker, Let us know what the LED does when the phone rings.
  6. audioguru2

    0h help. I need help with FM telephone bug!!!

    Kecker, The author of this project is Canadian, and uses the same phone system that you have. The text explains exactly how to hook it up, even the red and green wires colors. It is simply hooked-up in series with 1 wire between the jack and the phone.
  7. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    MP, Look even again. Not a single opamp in your schematics has a floating input, like our original IR project. Of course, in many cases (inverting amplifiers) the non-inverting input doesn't use a resistor for bias, but is simply connected directly to ground for its voltage reference. The same...
  8. audioguru2

    knight rider led modifications????

    New, It looks good, except: 1) A wire is missing between pin3 of the 555 to pin 14 of the 4017. 2) A 470uF capacitor is missing from VDD to ground. 3) The 5 ohm variable resistor should be about 50K ohms. 4) If you put the 560 ohm resistors at the transistors, then you need only 6 instead of 10...
  9. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    MP, Look again. ALL of the opamps in your schematics have their non-inverting input biased to ground: 1) A direct connection to ground. 2) DC coupling to a preceding stage that has its input biased to ground. 3) A resistor to ground. The latter is what I recommended in the IR project. A similar...
  10. audioguru2

    Electronic Stethoscope

    MP, 50 days after I corrected it, the circuit in our projects section still shows opamps running open-loop, without feedback. This has frustrated Cdak, and now Shiva. The errors are still not simply corrected. The original author's site shows similar frustrations. Cdak gave-up with this circuit...
  11. audioguru2

    Electronic Stethoscope

    Shiva, As you have found, this project has errors. Have you made corrections that I recommended? They are here:
  12. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    MP, Of course the input of an opamp is floating. It is waiting for a designer to connect it to a voltage reference, drawing an extremely low current. If you are not going to properly voltage-bias the opamp by simply adding ONLY ONE resistor, then it cannot provide its gain of 101, as determined...
  13. audioguru2

    Diana needs help about NCS2001 amp

    Diana, You have selected a voltage amplifier that is not designed to provide power to drive headphones. It is specified with a minimum load of 2000 ohms, and your headphones are probably 32 ohms or less. Even if it was capable of driving headphones, the volume would be very low because your...
  14. audioguru2

    knight rider led modifications????

    Attachment again:
  15. audioguru2

    knight rider led modifications????

    New, The CD4017BCP has an absolute maximum supply voltage of 20V. To protect it from alternator spikes, put a 100 ohm resistor in series with its supply terminal and a 470uF capacitor from its supply terminal to ground. That's right, the 560 ohm resistor is in series with the TIP31's base...
  16. audioguru2

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

    Xenobius, The circuit should work fine, but I didn't check the power ratings for its many resistors.
  17. audioguru2

    wireless control of dc motors ie infa red

    Patrick, It will be fairly easy to control 1 motor at a time with IR, and a switch to select which motor. But it is very difficult to design an IR circuit that must share signalling of 2 motors simultaneously. Can you post a schematic of the whole circuit and the speed controllers?
  18. audioguru2

    was Re:Ir-remote Now is: Op Amp discussion

    MP, Of course opamps need an input bias voltage. Without it, the floating input is pulled to the positive rail by the uncharged input capacitor during power-up, then the input is pulled to the negative rail by the base bias current of the opamp's NPN input transistor. Either condition results in...
  19. audioguru2

    knight rider led modifications????

    New, The TIP31 is better than the TIP29, don't let its metal tab touch anything and use a 560 ohm base resistor. There is no need to reduce the supply voltage, the parts will become just warm. Reducing the supply voltage would only make the lights very dim.
  20. audioguru2

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

    Xenobius, So you want me to custom-modify this project for your custom-made transformer? OK, here goes: 1) The 30VAC, 5A winding is rated for 150VA. Therefore the maximum continuous DC output current is only 3.5A. Fully loaded, the peak of the 30V sine-wave is 42.4V, but could be only 40.4V due...
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