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  1. Arouse1973

    -3db point on RC filter not @ -45deg

    Just done some calculations and this is what I have found. An example of capacitors parallel resistance is as follows. 100uF @ 159Hz ESR=0.01R Rp= 1/GP=ESR*(1+Q^2) Q=XC/ESR Xc= 10 So 0.01*(1+(10/0.01)^2) = 10,000R This could be what is causing the reduction of gain which is changing the...
  2. Arouse1973

    -3db point on RC filter not @ -45deg

    Ok, the only other way I can think of your circuit being effected is somehow loosing gain else where and not through the capacitor. This could happen if you have some parallel resistance. If you have a 1K and a 1uF then with 10K parallel resistance the phase at 3dB is about 39 degrees. Adam
  3. Arouse1973

    help me out with lm3914

    What is it suppose to do might be a good place to start. Also make some measurements on the circuit and tell us what you are seeing or not seeing. Adam
  4. Arouse1973

    -3db point on RC filter not @ -45deg

    I tried this with a 1u and 1K and got pretty close. So could it be your set up? What frequency did you get -45 phase shift at then? should be about 101Hz.. How are you measuring the values? Capacitors value can change with applied voltage and will depend on the type, electrolytics are quite...
  5. Arouse1973

    -3db point on RC filter not @ -45deg

    I have done an experiment using a 1K and a 1uF electrolytic. At 159Hz gave a phase of -43.5, gave -45 degrees at 161Hz. I swapped the cap for ceramic 100nF and resistor for 100K. At 159Hz gave a phase of -44.4 degrees, gave -45 degrees at 160Hz. Oh one other thing that I didn’t mention is...
  6. Arouse1973

    Frequency Detector

    Can you post the circuit diagram and the PCB if you have one. Adam
  7. Arouse1973

    -3db point on RC filter not @ -45deg

    Can you give us the actual component values and the frequency you were using if different from 100Hz. I'll do a quick test later myself with a proper scope.
  8. Arouse1973

    low voltage corrector

    You'll get 576 rms volts on the output. But that's a very high voltage which could kill you in an instant. I do hope this is a theoretical question and your not planning on actually doing this. Adam
  9. Arouse1973

    -3db point on RC filter not @ -45deg

    I have amended my chart to explain what I mean. Thanks Adam
  10. Arouse1973

    -3db point on RC filter not @ -45deg

    Yes agreed if he matched the input signal to the new 3dB point now shifted due to component tolerances. But if he keeps the input at 100Hz and then compares this to the output won't he see a phase different to what he is expecting? Adam
  11. Arouse1973

    Another Bat Detector

    Yes agreed.
  12. Arouse1973

    Component questions (transistor, capacitor)

    It will depend on what current you are supplying to the LED. If they are the standard 20mA 5mm LEDs then I would have thought any small signal transistor switch would work. Something like a BC557. Here is a link to some transistors...
  13. Arouse1973

    Another Bat Detector

    I think the output stage needs a bit of work. The counter is going to output digital and your caps are going to block this so all you will get is a nice under damped ringing after the leading edge of the output of the counter signal. You need to remove the cap on the output, and what is D1 for...
  14. Arouse1973

    Level Shifting

    Do you not just need a transistor switch?. See attached. Thanks Adam
  15. Arouse1973

    -3db point on RC filter not @ -45deg

    I think it's all about component tolerances which is why simulating without tolerance taken into account will sometimes give a result that is different from real life. I have done this for you to show some differences. The top set of figures show 5% on the resistor value and 5,10,20% on the cap...
  16. Arouse1973

    Re-wiring a powered Subwoofer

    Yes please post the diagrams here. Adam
  17. Arouse1973

    Speed measurement

    Ok I think this can be done as follows. You are going to need: A clock generator x 1 A pulse generator x 1 And associated timing components. AND gates 4 bit counter x 2 Quad flip flop x 2 BCD to seven segment display driver x 2 And current limiting resistors for the display. Good...
  18. Arouse1973

    Speed measurement

    Yes that will work. I'll let you know how to do it without a micro. Give me a bit of time.
  19. Arouse1973

    Home theater hum when source device is off

    Um sorry didn't quite get all that. What's blue tooth got to do with anything. Can't you just turn it off if not using it. Amplifiers may buzz a bit if turned up with no input. Adam
  20. Arouse1973

    Led project

    What do you mean directional. LEDs are certainly that, they are not like a light bulb. Adam
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