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  1. D

    Removing pre-load voltage difference for a load cell

    With a 10 bit ADC, you are already kinda sitting in the noise floor of your ADC. 4.88 lbs per bit is not very good if you need 5lbs of accuracy. I usually shoot for 10 x precision of what I am trying to measure. I assume the Arduino 10 bit input is a built in ADC input, correct? You may need to...
  2. D

    Amp dangers from a universal power supply adapter

    Remember, your AC/DC adapter is a constant voltage source, not a constant current source. V=IR and all that. Almost all consumer electronic power supplies are constant voltage sources. You will rarely have a constant current source provided in a consumer product.
  3. D

    RF Design Guidelines

    Thanks for all the responses. I pitched the copper tape idea using kapton tape layers and foil to impedance control, it was shot down as "arts and crafts." 125MHz isn't very fast, but we have a very critical engineering crew. I think I have a solution. Thanks again.
  4. D

    A failing converter unit.

    You really need an oscilloscope. Add one part at a time, checking your waveforms with each addition. Isolation transformers are always good because it keeps 240VAC from "electricfying" the case of the converter you are building. 240VAC both leads are typically "hot."
  5. D

    RF Design Guidelines

    My take on RF in electronic design has always been, if the wavelength of the frequency you are working with is less than 10 times the length of the board/device(s), you should be using impedance matched networks for traces and cabling. Currently I have a problem where the wavelength is the...
  6. D

    Brushless DC motor text book

    I'm looking for a textbook that has an in depth coverage of brushless DC motor physics as well as control theory. -indepth mathematical approach as well as conceptual theory -controller schemes and design fundementals -mathematical study of induced currents on the stator/rotor, and what this...
  7. D

    Extra power from 40 mph exhaust fan

    Instead of trying to harness the wind, harness the heat loss off the fan motor. Use thermals engines like sterling motors to turn tiny generators and trickle charge batteries. You don't get perpetual motion but atleast your system efficiency goes up.
  8. D

    Fermi Level Statistics

    Nice, thanks.
  9. D

    Fermi Level Statistics

    Thanks for the replies guys. I think it is possible since I can't find any outstanding errors in my math or my assumptions.
  10. D

    Fermi Level Statistics

    This is sort of a simple question. In a steady-state semiconductor doped n-type, is it possible for the quasi-Fermi level for the holes (F sub p) to be above the intrinsic level for the conductor (E sub i)? That is, E - F = (negative value)?
  11. D

    Curl and Divergence (flux, and what not)

    Just a follow up incase someone else needed the same solution. Merely expanding the cross product (<P,Q,R> form as \vec{G} ) leaves a vector in differentials that is equal to \vec{F} . From then its just a matter of setting the components equal to each other and knocking off which ever...
  12. D

    Curl and Divergence (flux, and what not)

    http://astron.berkeley.edu/~jrg/ay202/node189.html [Broken] ? 14.54 gives me the form, such that A = G, but does this mean B = F if I expanded to 14.51?
  13. D

    Curl and Divergence (flux, and what not)

    I'm having a bit of difficulty with this problem: \vec{\nabla} \times \vec{G} = \vec{F} where \vec{\nabla} \cdot \vec{F} = 0 and \vec{F} = <y, z, x> . Find \vec{G} . I'm really at a loss how to solve this. I know the solution must be quick and easy because it was on a quiz. What...
  14. D

    Heatsink Recommendations for xp-3000

    Thanks for the replies, ended up going with swiftech and artic silver. Averaging 60C. As to case fans, I have so many I had to get a 450W Enermax. I have an 80mm in back just under PSU pulling hot air out, two side mounted 80mm's blowing over graphics card and motherboard, and a 120 mm blower...
  15. D

    Yet another electric feild problem

    Thanks for your replies guys, with this simple elightenment begins the blossoming of understanding, and also 5 more homework points. :D
  16. D

    Heatsink Recommendations for xp-3000

    Having problems with stability on new xp-3000. I just realized my cpu is cruising at a 'cool' 75 C. Fan I'm using is a YSTech something or other 47 CFM. I figure the fan is fine thinking 47 CFM is quite high. Any ideas for heatsink? Right now I'm using a boxed aluminum heatsink from a 1.3...
  17. D

    Motorcycle Catches a Car

    What you need is the basic idea of acceleration, velocity, and position with respect to time. With some integrations holding a as constant you end up with: V(final) = V(intial) + AT (used for maximum velocity) x(final) - x(initial) = V(intial)T + (1/2)A(T^2) (distance formula) Using...
  18. D

    Yet another electric feild problem

    The question actually asks: What is the magnitude and direction of the field at P due to the two charges at the base? Does that mean to neglect the top charge?
  19. D

    Yet another electric feild problem

    This one I'm having a bit of conceptual difficulty with. Problem is: three positive point charges, q, are placed in an equal lateral triangle, charges being the vertex's. Length of one side is a. Calculate the electric field at point P, which is also the the location of the topmost charge...
  20. D

    Electric Feild help

    Thanks, I think I have something to turn in at the least now. :p
  21. D

    Maximum speed attained

    Your asking the maximum speed attained, which is the magnitude of the velocity. From what I gather of the problem, the ship has positive acceleration for a period of 15.9 minutes, a constant velocity, then a negative acceleration for a period of 15.9 minutes. Your equation is the distance...
  22. D

    Maximum speed attained

    Yes, that is first year college mechanics.
  23. D

    Maximum speed attained

    I believe you only need to use V(final) = V(intial) + at. Since intial is 0? then your maximum speed would be acceleration * time interval of 15.9min? So converting that to seconds gives (19.8 m/s^2) * (15.9 min * 60 s/m).
  24. D

    Electric Feild help

    I just recently began the Electricity and Magnetism course. Having said that I'm requesting help with a general plan of attack for two homework problems, that is, conceptually understanding how to use the math on these problems. First problems states there is a hollow cylinder of length h...
  25. D

    Chem question

    I wasn't under the impression we were obligated to read all the threads.
  26. D

    Ge-Force FX 5200

    Tom's Hardware is good for checking benchmarks and what have you. RMA basically means return for refund + redtape. As far as cpu's are concerned, four months ago I would have recommended a p4/ddr500 combo, but as of right now who knows. I don't really go for the Intel is to Nvidia as AMD...
  27. D

    Ge-Force FX 5200

    I recently purchased a Radeon 9800 Pro. Very satisfied. Before giving in and buying an ATI I did however buy a Geforce FX 5900 Gainward, which I had to RMA, twice. And now looking at current benchmarks in games I'm very much so grateful that the Nvidia cards came DOA. With the current 9800...
  28. D

    Whom do you think will win the X-Prize and why?

    Scaled Composite's design is seemingly new in make though perhaps not in theory. Economics and reusability seems to be the focus of this X-Prize contest more so then just being original. SC's design is highly reusable, and very fuel efficient.
  29. D

    Chem question

    Just off the top of my head I would say the study of atoms, molecules, and subatomic particles on a system and how they react to surroundings and each other. Physics and chemistry have a lot of overlap. The dictionary definition is as follows: "That branch of science which treats of the...
  30. D

    Potentially useless

    Thanks for your replies. Your posts remind me of the mathematical induction chapters in a few of my math books. I think my programming classes are overwriting the nerons in my brain.
  31. D

    Potentially useless

    I found this scratching away on a piece of cardboard today. I thought I might troll the board and see what people think. Bare with me for I sometimes have trouble expressing what's in my head in words. As follows: Take the highest whole number median of an odd integer x and multiply it by...
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