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  1. audioguru2

    Our "DC Motors" article

    Who writes that stuff, anyway? According to the article, in the 1st "Common Motor Applications Problems", if you take a tiny little low-torque DC permanent-magnet motor, and use additional batteries in parallel, then its torque will be increased! Oh yeah? Not only that, but in the 2nd Problem...
  2. audioguru2

    How to increase reactance in a coil of few turns?

    Thrival, I am sorry but I don't see your oscillator and can't find your book. The only way that your circuit could oscillate is if the transistor is a unijunction, which it ain't. I'm sorry to hear that your IGBT died. Without any protection, it probably would have blown if the load disconnected...
  3. audioguru2

    How to increase reactance in a coil of few turns?

    All that I see is a fuse-blowing circuit: 1) The IGBT feeds its half-wave 60Hz pulses into the 12 turns primary (dead short) of the transformer. 2) The 120VAC mains is rectified and filtered with 4 RC filters, developing about 42VDC (when the 1K pot is at maximum) which far exceeds the 20V...
  4. audioguru2

    inductors and arching

    Hotwaterwizard, Ouch!! Excellent demonstration! ;D
  5. audioguru2

    Grounding of Neutral? conductor on boats.

    Mouse, If you "float" your circuit, then you are relying on the marina or your inverter's manufacturer to test the insulation and ensure that the insulation has not become damaged by wear-and-tear. Dangerous. Over here, outdoors appliances are"double-insulated" so that the insulation has a back-up.
  6. audioguru2

    reliablity of hFE

    Shekhar, If you are talking about biasing the base of a common-emitter transistor, then you won't know what the value of hFE will be. See the data sheet for the 2N3904 transistor here: http://www.fairchildsemi.com/ds/2N/2N3904.pdf 1) Page 2 shows that at room temperature, the hFE can be from 30...
  7. audioguru2

    detect broken wire without removing the rubber

    Ante, Sure, just let your high-voltage arc set the insulation on fire, then your eyes and nose will detect the break!
  8. audioguru2

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

    Kobus, With the mains voltage 10 percent high feeding a 30VAC, 7.5A transformer, with the project unloaded, the positive and negative supply voltages to the ICs add up to about 54V. Very few opamps are rated for that and therefore are pricey. The LM143/343 has been discontinued by National...
  9. audioguru2

    0-30 Vdc Stabilized Power Supply

    Kasamiko, and others, My replies in this forum and the Parts List that follows will allow this project to meet its own specs and to operate reliably. Parts List for 3A Variable Power Supply *T1 = 30VAC, 4.3A, 130VA stepdown power transformer *R1 = 2,2 KOhm 2W R2 = 82 Ohm 1/4W R3 = 220...
  10. audioguru2

    detect broken wire without removing the rubber

    Keile, Welcome to our forum. If you can make a broken wire that carries current to a load like a light bulb become intermittent by bending, pushing the break together and pulling it apart so that the light bulb flashes, then the break location can be detected with an AM radio that is tuned...
  11. audioguru2

    low pass filter

    Kevin, With a single-stage filter, there is no way to control the filter characteristic: a Bessel or Butterworth will both be the same, with a droopy 20dB/octave roll-off. With a multiple-stage filter, a Bessel has a droopy, broad and undefined corner frequency, while a Butterworth uses feedback...
  12. audioguru2

    Electronic Stethoscope

    Only 3 of my changes are important and were also discussed by other members. The other changes only make it better (low-noise microphone preamp, etc). Has ANYONE made this project work without any changes?
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    Fail so much? No, only occasionally. I'm sorry that I am not absolutely perfect like you. Where are your discussions for this project? What's your big problem with my recommendations of project improvements for members?
  14. audioguru2

    Blinking LED

    Quantum, 4001 diodes will work fine in your 9V, 2-transistor circuit. You need 2 diodes, 1 for each transistor. 1N numbers are assigned to diodes and 2N numbers to transistors in sequence, unfortunately the numbers don't mean anything, just pointing out the assigned component. Its specifications...
  15. audioguru2

    idea of infinite energy

    Shankar, Noise has a high peak voltage, but it is only momentary, random and varies its polarity. If you want to make a power source from noise, then connect a long outdoor antenna to a rectifier and filter capacitor to ground. The average power output of this power source will be very low...
  16. audioguru2

    inductors and arching

    Kevin, 1) Why do transistors have an absolute maximum voltage rating? 2) What happens to a transistor that has a 40V absolute maximum voltage rating and you put 400V or more across it from a non-protected inductor load? 3) Why not use a cheap protection diode instead of an expensive high-voltage...
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    MP, Kobus, not I, is building this project and has asked for advice to modify it for 5A output current. I gave him advice. ;D Didn't you see Capricious's recent serious problems with very high temperatures with this project, even when using less output current? :'( Ask Mixos how poorly his...
  18. audioguru2

    Electronic Stethoscope

    MP, No, I wasn't wrong: 1) Tomah's project didn't work until he made a change that I discussed above. 2) Shiva's three circuits had no output from U5 without this change, but his computer simulation did not catch this error and therefore worked. I'll bet that Tomah's earphones' impedance is much...
  19. audioguru2

    Blinking LED

    Quantum, The circuit is symmetrical so should alternate the lighted LED with similar timing as the other. If you are using a supply voltage that is more than about 6V, then you should connect a diode between each transistor's emitter and ground (cathode to ground), so that the timing is not...
  20. audioguru2

    inductors and arching

    Shekhar, When a DC current flows in an inductor, a magnetic field is built-up in its core. When the current flow is stopped by opening a series switch, relay or a driver transistor, then a very high reverse voltage is produced across the coil as the magnetic field collapses and induces the high...
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