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  1. L

    Calculate Current, Power, EMS..

    I have attached the MathCAD page illustrating how I would write the node equations for nodes A & B, first for the general case with node C active and then for the specific case with node C as the ground reference (Vc=0). Only provided the solution for the two node voltages since that is what...
  2. L

    Can one coil be a generator?

    When a piston is connected to a flywheel does that not provide for the continual exchange of linear momentum and angular momentum, minus energy lost to friction and work done by the piston such as generating electricity? At the start of this thread the OP stated a desire for artistic uniqueness...
  3. L

    Calculate Current, Power, EMS..

    Curious as to why you choose the ground reference as an isolated node between two resistors instead of a node that is a common point for the most circuit branches. If you made node 'C' the circuit ground, then how many equations would it be necessary to write? Is it ever necessary to get the...
  4. L

    RC Circuit from Voltage equation

    Compare the given discharge equation to a common RC discharge equation. How does the variable 'T' compare to the RC time constant 'tau'? There are many different values of R and C that will give the required value for 'tau'.
  5. L

    Calculate Current, Power, EMS..

    Constructing the node equations with a slightly different method yields the same numerical result, see attached MathCAD page.
  6. L

    Project using a strong 12 volt motor

    Wouldn't the current drawn by the motor vary with the load placed on the motor? The highest possible current would be the stall current. In the car what is the rating of the fuse on the circuit with the wiper motor?
  7. L

    Future of electronic jobs?

    What level of education is it necessary to achieve in order to be given that level of support? Do any but PhD's get to work on the really interesting stuff?
  8. L

    C-EMF and a coil?

    Not sure that C-EMF is the proper term to be used in this situation. While C-EMF is sometimes mentioned when discussing Lenz's Law, that topic is primarily concerned with the direction of induced currents and not EMF, counter or otherwise. C-EMF is a term primarily applied to the armature of...
  9. L

    Calculate Current, Power, EMS..

    In the nodal method you write the node equations for a circuit which are an application of KCL stating that the sum of all current leaving a node must be zero. For any node the node equation expresses the current for any path as the potential difference to an adjacent node multiplied by the...
  10. L

    Op Amp - what am I missing

    The datasheet for the TL084 shows the input bias current to be up to 200 pA and up to 10 times that over the full operating temperature range. So where does that DC current flow in the '+' input circuit? I doubt the DC current will flow through the piezo crystal.
  11. L

    Calculate Current, Power, EMS..

    In your diagram there are branch currents I3 & I4 and I1 & I5. But I3 is the same current as I4 and I1 is the same as I5. Does it really make sense to write equations using I4 and I5, and then have to write additional equations I4=I3 and I5=I1? It would also simplify the algebra, at least for...
  12. L

    Operational amplifiers

    R2=46K is the correct answer. But how can you be sure? Look at the schematic for the non-inverting amplifier. Realize that whenever an (ideal) op amp is in its linear operating range the voltage at the '+' and '-' inputs has exactly the same value. Here the voltage at the '-' input is the...
  13. L

    Calculate Current, Power, EMS..

    OK, the redrawn circuit looks good to me, but that may just be the tequila talking. Note there are three possible current loops. Upper, Lower, and Outer loops. When choosing loops the only requirement is that every component must have at least one loop current passing through it. You have...
  14. L

    Calculate Current, Power, EMS..

    The wiring diagram specifications provide four different circuits. Draw the circuits individually with the specific values given for each case, leaving out the components that do not apply, and there is no need to draw the voltmeter for the circuit analysis. For the case requiring nodal...
  15. L

    Help with simple circuit/opamp project

    Drive your sensor with a current source that will generate 5 volts to ground at the sensor's maximum resistance. 15 uA for 330 Kohm, 150 uA for 33 Kohm. Connect one end of the sensor to ground, the other end of the sensor to the current source & micro-controller analog input. You could place...
  16. L

    capacitors as batteries?

    Q - coulombs (1 coulomb is the electrical charge of approx 6 quintillion electrons) V - volts C - capacitance in farads I - current in amperes (one ampere is the flow of one coulomb per second) So the more useful equation is I*T=V*C or I*(delta T)=C*(delta V) The rate of capacitor...
  17. L

    Finding Current and Voltage in a series parallel combination

    Attached files illustrate two methods for calculating voltages in a resistor network. The pdf shows successive calculation of equivalent resistance for portions of the network so that voltages may be found from a resistor divider arrangement. The png shows the node equations from which the...
  18. L

    Need the circuit design

    It seems that you need a simple inverting op amp with unity gain (-1) and a virtual ground offset to +2.75 volts. Choose an amplifier & power supply so the linear operating range includes 0.5 to 5 volts.
  19. L

    Finding Current and Voltage in a series parallel combination

    The usual method for calculating the performance of resistor networks is to substitute an equivalent resistance, Req, for the network. Do this by combining individual resistors. Combine parallel resistors into one resistor. Combine series resistors into one resistor. Keep doing this until...
  20. L

    ad 620 instrumentation amplifier

    If that is a capacitor in series with the '+' input then you need to read the following document: "Applying Instrumentation Amplifiers Effectively—The Importance of an Input Ground Return" http://www.analog.com/static/imported-files/overviews/85019004In_AmpAdvertorialFINAL.pdf
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