Search:

Type: Posts; User: c_mitra

Page 1 of 20 1 2 3 4

Search: Search took 0.03 seconds.

  1. Replies
    19
    Views
    421

    [SOLVED]Closed: Re: Wiring of DC fans in Series

    The small DC fans are more resistive than inductive. I do not see any problem with your idea.

    But look carefully: some of the modern cooling fans used in small cabinets are brushless DC and they...
  2. Closed: Re: PCB flexion and cracking of SMD capacitors

    I am not so sure.

    Bigger size also means physical strength. But how does it scale?

    Flexing causes bending stress; for a given amount of flexing, the stress will be now proportional to the area...
  3. Closed: Re: PCB flexion and cracking of SMD capacitors

    Assume the screws are nicely fixed; then major flexing can occur only on the long axis. Components that are mounted along this length shall experience the greatest stress.

    I presume that...
  4. Closed: Re: Is a tantulum different from a microfarad tantulum cap?

    Yes. Tantalum is a metal, like Aluminium or Titanium. Tanatalum capacitor is a special kind of electrolytic (mostly solid; unlike aluminium electrolytic ones) capacitor that uses Ta (it is symbol of...
  5. Replies
    84
    Views
    3,492

    Closed: Re: Extracting energy from gyroscope precession

    You are not being honest in your experiments.

    If you lean back sitting on a swing so that your centre of gravity shifts outside the seat, you will fall off.

    You need to hold on to the ropes to...
  6. Replies
    11
    Views
    522

    Closed: Re: BLDC motor delta winding

    I do not see any problem with the scheme outlined in post #4. Basically you will see waveforms of phase 1 and 2 and 3 (provided the phases do not change very rapidly).

    You need to see the...
  7. Replies
    2
    Views
    1,535

    Closed: Re: I have a question about PCB recycling

    The metals are reusable; copper, gold, palladium and nickel. I have been told that the amount of gold present in waste PCBs is more than that present in common ores.

    The epoxy (thermoset plastic...
  8. Replies
    16
    Views
    652

    Closed: Re: problem with pcb etching

    Perhaps the Hydrogen peroxide is too weak; use a stronger solution. Etching for a longer time will get you a poorer quality.
  9. Replies
    84
    Views
    3,492

    Closed: Re: Extracting energy from gyroscope precession

    But this effect, not really mysterious, is actually due to air friction. If you have an open umbrella in your hand, it is trivial. It is the same air friction that (mainly) is responsible for the...
  10. Replies
    84
    Views
    3,492

    Closed: Re: Extracting energy from gyroscope precession

    You are right.

    Conservation of energy is a stronger notion in this case.

    Rotational speed goes up because the moment of inertia goes down.

    Ignoring friction, the angular momentum shall also...
  11. Replies
    49
    Views
    1,910

    Closed: Re: Driving 140x 3W LEDs

    Sadly, no.

    Like Audioguru has pointed out the reference voltage can be off by +/-5% (although most will be pretty close). In the same way, resistor values are often off by +/-20% (although you...
  12. Replies
    84
    Views
    3,492

    Closed: Re: Extracting energy from gyroscope precession

    Compare and contrast a real experiment.

    The famous Foucault's pendulum.

    The plane of the pendulum can be considered to be the plane of the spinning wheel. For a spinning wheel the angular...
  13. Closed: Re: Design and construction of scintillometer for evapotranspiration

    The basic principle is simple.

    To use the stated method, you need to focus on one of the strong absorption band. N2 does not absorb in the IR but there may be Raman scattering possible (you need...
  14. Replies
    49
    Views
    1,910

    Closed: Re: Driving 140x 3W LEDs

    Whereas this is correct in principle, you should focus on the final objective. The LEDs should get the same current and provide uniform intensity. Therefore the individual LM317s should have...
  15. Closed: Re: -3db frequency of the op-amp open loop gain

    Usually it is 3db power or gain point; -3db is approximate equal to 50% of the original gain (sometimes power) and 3db is similarly equal to double (twice) the gain.

    3db=0.3 bel=10^(0.3)=1.995
    ...
  16. Replies
    84
    Views
    3,492

    Closed: Re: Extracting energy from gyroscope precession

    This page http://hosting.astro.cornell.edu/academics/courses/astro201/earth_precess.htm says that the precession period is about 26000 years.

    Yes, you are right when you invoke external...
  17. Replies
    39
    Views
    2,856

    Closed: Re: Single conductor inside hollow conductor

    There is no way to ensure that the CT is not introducing any phase shift. So if you want to measure the phase of the current, you should not use the current transformer at all...

    By the way, phase...
  18. Replies
    84
    Views
    3,492

    Closed: Re: Extracting energy from gyroscope precession

    Things can be confusing but I am not here to add more.

    In Cartesian space, you have motion on a straight line, kinetic energy is (1/2)m.v^2. This v is nothing but dx/dt.

    Lagrange made lots of...
  19. Replies
    39
    Views
    2,856

    Closed: Re: Single conductor inside hollow conductor

    I presume these are RMS values. I agree with what FvM says (#35) but it may not be a bad thing considering the simple design principles.

    But I have forgotten the original question (I was away for...
  20. Closed: Re: Is it possible to make an IGBT to work at duty cycles up to 100%?

    I presume you got the idea by now.

    If you see the waveforms in the typical datasheets, they do not appear square, they are trapezoidal. And there is a reason for that.

    You cannot go from 0v to...
  21. Replies
    84
    Views
    3,492

    Closed: Re: Extracting energy from gyroscope precession

    I am sorry that I am not understood.

    Motor is a source of energy. A gyroscope must be free (from external forces)- I am talking about mechanical gyroscopes here.

    A spinning object mounted in...
  22. Replies
    3
    Views
    349

    [SOLVED]Closed: Re: would iron wire block high frequencies

    Yes, but thin wires will have only a small effect. Imagine a straight long iron wire carrying some current. The magnetic lines of force will be circular, perpendicular to the wire and will see only a...
  23. Closed: Re: Is it possible to make an IGBT to work at duty cycles up to 100%?

    Right.

    If you want a 100% duty cycle, why do you need a switch at all? It is not going to be turned off, right?

    But how a chopper is going to work with a 100% duty cycle? MY knowledge is...
  24. Replies
    49
    Views
    1,910

    Closed: Re: Driving 140x 3W LEDs

    I believe the LEDs have already some form of heat sink- there is a central pad on the reverse which is expected to be soldered to a board (in this case the PCB). With 70 LEDs dissipating 3W each...
  25. Replies
    49
    Views
    1,910

    Closed: Re: Driving 140x 3W LEDs

    I do not think the 24R is god-given; you need to calculate the value based on your current requirement. The reference voltage is 1.25V=700mA *R; that makes R=1.8 Ohm; this should be rated at...
Results 1 to 25 of 500
Page 1 of 20 1 2 3 4