Search results

Search Forums New Posts
  1. L

    Diode balanced mixer

    My concept of a mixer is that the diode is used to approximate a commutator and that the switching of the commutator is controlled by the local oscillator. Does it make any sense to speak of signal voltage across the diode when the diode is forward conducting, or when it is reverse biased? Is...
  2. L

    Basic Capacitor Question

    Yes, such things are possible. But first consider how long the 150mA current must flow, and whether the circuit will still operate correctly as the capacitor voltage decreases over that time period. Capacitance is defined as the charge stored per volt, C=Q/V, where charge (in coulombs) equals...
  3. L

    Help for Pitch Shift Circuit

    The software at the following sources may be all you need. For doing pitch shifting in hardware you would need to digitize the analog audio, write the digital stream into storage at a constant rate, and read the stream out at a different rate for playback. The time delay will need to be large...
  4. L

    Help for Pitch Shift Circuit

    The question was whether you really wanted to do pitch shifting or frequency shifting?
  5. L

    Help for Pitch Shift Circuit

    I don't quite understand the problem statement. Isn't the magnitude of a semitone proportional to the octave the signal is in? So a proportional shift would imply pitch shifting. In that case the playback of upper and lower signals would occur over different time durations so you would be...
  6. L

    Minimize logic expression for each segment in 7 segment LED

    Here is an example of using a spreadsheet (OO.o Calc) as a logic simulator. The conditional formatting effects do not seem to carry through if you open the .ods file in Microsoft Excel. Segment 'd' seems to have a problem for the BCD value 0110.
  7. L

    Circuit Help!

    That's like saying, "Having possibly vulnerable cockpit doors does not equate to the Twin Towers being knocked down." The USA has a vulnerable power-grid/computing/communications infrastructure that can be exploited by al Qaeda, North Korea, or Iranian Ayatollahs with nukes/missiles to force...
  8. L

    Circuit Help!

    See this article from the IEEE: http://www.todaysengineer.org/2007/Sep/HEMP.asp A short quote from the article follows - "An important new study by the Congressional EMP Commission published in 2004 [1], clearly indicates that the U.S. infrastructure is vulnerable to the possibility of even a...
  9. L

    Circuit Help!

    I once visited an EMP facility designed to test military equipment performance in a simulated EMP field like unto what would be generated by a nuclear detonation. The capacitors were the size of a small car, and you could tell the current would be large because wire was not used for...
  10. L

    RC circuit Transfer Function/bode plot

    @Mitchy190: I'm still using Mathcad 14, running on Windows 2003, running on a virtual machine in CentOS Security-Enhanced Linux 6 with a host-only network. (I would never expose a working copy of Windows to the internet.) As for how to plot a trasnfer function, I made a pdf copy of the...
  11. L

    RC circuit Transfer Function/bode plot

    I took your transfer function and had Mathcad display it as a Bode plot. If anyone does it the long way, I'm wondering if Mathcad provides an accurate graph.
  12. L

    Counter Help

    I would try using the counter to accumulate time between spokes. Use the spoke detection to reset the counter. If there is a carry-out before the next spoke then the wheel is rotating slowly. But if the spoke is detected before counter overflow then the rotational speed is too high. Or you...
  13. L

    Op-Amp premature clipping

    The datasheet for the TL022 uses a standard load resistance of 10K. The short circuit output current is a maximum of 6 mA. Whereas the load resistance here is almost 250 ohms so the output would be clipped at +/- 1.5 volts. That might explain why your signal output swings from 7 to 10 volts.
  14. L

    output power against load

    The general rule for power transfer is that maximum power is transferred to the load when the source impedance is the complex conjugate of the load impedance. But transformers are usually used only for resistive, and not reactive, impedance matching. In this case it seems that impedance...
  15. L

    integral derivative

    The difficulty here stems from the fact of dealing with an improper integral, in this case integrating over an unbounded region where the basic function never converges. Of course there are techniques for evaluating improper integrals but they all require convergence. Nevertheless, integrating...
  16. L

    incremental resistance of a diode

    Start with: I=P*V^(1.5) The general form for the derivative is d/dx U^n = n*U^(n-1)U' d/dV I = d/dV P*V^(1.5) = P d/dV V^(1.5) = 1.5P*sqrt(V) Incremental Resistance = dV/dI = 1/(1.5P*sqrt(V)) = 2/3 * 1/P * 1/sqrt(V)
  17. L

    Assignment help (basic queuing system)

    Are you using a segment decoder/driver with 1,2,4,8 inputs, or are you expected to design the segment driver from scratch? If the former, then input 1 = A, and input 2 = B but only if not A. So can you design a function that equals B AND NOT A?
  18. L

    NewFET device

    But really, what can one actually learn from solving equations manually? Especially for deriving operating curves for non-linear circuits? That is a monumental waste of time just to learn not to do it that way, i.e., it is much preferable to linearize the device model instead. Also, if he...
  19. L

    NewFET device

    Here is a solution from Mathcad v14. I have plotted each of the resulting functions for output voltage for some likely circuit values. You decide which is real. Note - Your .doc file caused me problems because it contains images given as URLs. Please refrain from doing that in the future.
  20. L

    Trying to create rotating device/minimum speed. Could use some advice!

    Does it need to be an electrical solution? Maybe you could add some more gears to the gear motor. Or add some pulleys to reduce the speed. How about a disk of quarter-inch plywood where the wood edge has been routed in the fashion of a pulley, attached to the back of the painting, and the...
Top