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  1. audioguru2

    "Cannot Connect", again and again

    Today the server is worse than it was before the long update the other day. I had to make many tries to log-in, going from page-to-page and trying to post gave errors. Once, the server gave the message, "too many connections".
  2. audioguru2

    OPAMP questions

    Kevin, The input capacitor does NOT cause the gain to increase. It simply rolls-off the low frequencies, below its "corner" frequency at 20dB/decade. The corner frequency is determined by the capacitive reactance and the source and bias resistors. Below the corner frequency, the capacitor passes...
  3. audioguru2

    How do I make a dc circuit auto-off after 60 minutes

    Uman, A project that uses the 4060 that I recommend is here: http://www.mitedu.freeserve.co.uk/Circuits/Timing/24hour.htm
  4. audioguru2

    Rocker Switch Query

    gEcky, 1) A quality switch should not blow-out. 2) I am still confused by your "+/- 24V" transformer. Is it 24V center-tapped, which is also 12-0-12? Then its rectified and filtered output is about 16.2V. 3) Your LED has about 1.8V (for red) across it. If you use a 220 ohm resistor in series on...
  5. audioguru2

    Re:Transistors discussion

    Output Transistors in Square-wave Inverter Circuits: 1) How much current must be drawn from a 12V battery to produce 300W output from a square-wave inverter circuit? Well, you need to draw at least 300W, plus some more to account for losses such as transistor saturation voltage-loss (which...
  6. audioguru2

    Re:Transistors discussion

    Hey! Who started this topic here and put my name on it? But let's continue without locking nor deletions: 1) The author's web-site's forum has 5 pages of complaints about this project with all-kinds of capacitors (tantalum, elecrolytic, non-polar) blowing-up. 2) One that didn't blow-up...
  7. audioguru2

    Re:Transistors discussion

    MP, Credit? Of course I'm proud of myself. Philips? While they were showing to me their top-secret audio-cassette and LED, I was teaching them about transistors. Been there, done that: Job? I'm playing with "Freedom 55" now, plus a little consulting on the side.
  8. audioguru2

    Project Help

    Ante, That's a good comparison, they both look almost the same, even with nearly 3:1 compression. What program do you use to convert GIF to JPG? Will it also convert BMP (huge file) to JPG?
  9. audioguru2

    temperature controller

    Equinox, Isn't the contol circuit just a thermostat that is designed for use with your heater? Isn't the heatexchanger just a fan that blows air through fins attached to your heater? Didn't they come with connections instructions?
  10. audioguru2

    Night rider scanner

    Nettron, I mentioned CMOS because Eki's kit doesn't appear to have LED current-limiting resistors. CMOS outputs current-limit at about 11mA from a 9V battery. I agree that linear will look better than logic, because the LM3914 "blends" between adjacent outputs, while logic will go: jerk, jerk...
  11. audioguru2

    Re:Transistors discussion

    Ante, In those days, few people except you and me knew much about transistor circuits! Those Philips engineers just didn't know, so uni-polar was chosen. For the capacitors in this project, most of the time the collector-side of the capacitor is positive: 1) During its charging when the...
  12. audioguru2

    Rocker Switch Query

    gEcky, That's good that your transformer isn't shorted. Your switch just "failed". A double-pole switch has 2 switching contacts. One for Live, and the other for Neutral. An LED needs a current-limiting resistor in series. The value and power-rating of this resistor is determined by the voltage...
  13. audioguru2

    How do I make a dc circuit auto-off after 60 minutes

    Uman, The 555 will time to 1 hour or more but you will probably have difficulty finding a very-low-leakage capacitor. It can be reset at any time with its reset pin. The CMOS version, ICM7555, due to its very low supply current, is recommended for your battery operation. Its data sheet is here...
  14. audioguru2

    Night rider scanner

    Nettron, Eki aren't using 18-pin LM3914s but are probably using the same circuit that you have, except using CMOS instead of your TTL. A quick check of Kinetics shows that a pendulum doesn't swing exponentially, but more like a sine-wave, since its inertia starts it swinging slowly, the same...
  15. audioguru2

    Re:Transistors discussion

    Ante, Wow, the AD149 brings fond memories. It was the 1st TO3 transistor that I have ever seen! Without wading through Google, I have a Philips 1969 transistor databook beside me (Philips was my 1st job), and that PNP germanium transistor's base-emitter junction did not avalanch (but the...
  16. audioguru2

    Power supply for AMP in CAR

    Ante, Yes, I agree that transistors from the same batch will have the same gain and therefore can be paralleled without emitter resistors. I also agree that changing them all together maintains their matching.
  17. audioguru2

    "Power?" Inverter

    Ante, I was agreeing with you when I mentioned computer wiring, since you mentioned wiring then I knew that you were also considering PCB trace sizes: In this project do you believe that the capacitors are shown with the correct polarity? Do you have any comments about its high capacitor...
  18. audioguru2

    Power supply for AMP in CAR

    MP and ANTE, Maybe they use more transistors than is necessary in order to reduce the gamble of a high-gain transistor "hogging" the current. Also, extra transistors are probably cheaper than having many emitter resistors. You didn't comment about my explanation for emitter resistors that I...
  19. audioguru2

    Transformerless power supply

    Ldanielrosa, Input capacitors will not provide isolation from the mains, since they pass the AC. If you use their capacitive-reactance like a series resistor, except without heating, then they will cause the rectified voltage to fluctuate with load changes (very high with no load and quite low...
  20. audioguru2

    Night rider scanner

    The exponential charge/discharge of a 555's timing capacitor IS like a pendulum! But the effect is reduced by the 555's lack of full charge and discharge (1/3 of +V to 2/3 of +V). So maybe it would be best to low-pass filter a square-wave in order to obtain an alternating voltage that changes...
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