In a sense this is a "homework" question. The catch is it is homework from 50 years ago in a first semester of DC circuits ;/ The immediate problem is quite simple. It is a 2 port network of 6 components with 2 internal nodes. It is driven by a ideal voltage source and I want to solve for the open circuit output voltage. It actually would have been suitable homework. Pointer to suitable refresher site please. P.S. I do expect to say *DUH* when recalling how to solve.
A "back to basics" question
Started by ●June 21, 2013
Reply by ●June 21, 20132013-06-21
On 21.6.13 4:43 , Richard Owlett wrote:> In a sense this is a "homework" question. > The catch is it is homework from 50 years ago in a first semester of DC > circuits ;/ > > The immediate problem is quite simple. It is a 2 port network of 6 > components with 2 internal nodes. It is driven by a ideal voltage source > and I want to solve for the open circuit output voltage. It actually > would have been suitable homework. > > Pointer to suitable refresher site please. > P.S. I do expect to say *DUH* when recalling how to solve.The canonical way is to write the loop equations, using Ohm's and Kirchhoff's rules: - the voltage over a resistor is resistance multiplied by current, - the sum of currents in any node is zero, - the sum of voltages around a loop is zero. There will be a linear equation group to solve, but it may be tedious. Depending on your circuit, it may be possible to simplify it using the wye-delta transform and Thevenin's or Norton's theorems. -- Tauno Voipio
Reply by ●June 21, 20132013-06-21
>On 21.6.13 4:43 , Richard Owlett wrote: >> In a sense this is a "homework" question. >> The catch is it is homework from 50 years ago in a first semester of DC >> circuits ;/ >> >> The immediate problem is quite simple. It is a 2 port network of 6 >> components with 2 internal nodes. It is driven by a ideal voltagesource>> and I want to solve for the open circuit output voltage. It actually >> would have been suitable homework. >> >> Pointer to suitable refresher site please. >> P.S. I do expect to say *DUH* when recalling how to solve. > > >The canonical way is to write the loop equations, using Ohm's and >Kirchhoff's rules: > - the voltage over a resistor is resistance multiplied by current, > - the sum of currents in any node is zero, > - the sum of voltages around a loop is zero. > >There will be a linear equation group to solve, but it may be tedious. > >Depending on your circuit, it may be possible to simplify it >using the wye-delta transform and Thevenin's or Norton's theorems. > >-- > >Tauno Voipio >Circuit simulators are super good at solving 'tedious' networks. _____________________________ Posted through www.DSPRelated.com
Reply by ●June 21, 20132013-06-21
>In a sense this is a "homework" question. >The catch is it is homework from 50 years ago in a first semester >of DC circuits ;/ > >The immediate problem is quite simple. It is a 2 port network of >6 components with 2 internal nodes. It is driven by a ideal >voltage source and I want to solve for the open circuit output >voltage. It actually would have been suitable homework. > >Pointer to suitable refresher site please. >P.S. I do expect to say *DUH* when recalling how to solve. > > > >http://en.wikiversity.org/wiki/Electric_Circuit_Analysis Try that website, I have not verified its contents, but looks decent. Simplify impedances as much as possible (parallel, series combos) then do loop/node equations as necessary. Long hand is fun sometimes, instead of using simulators. I am starting to feel people rely on simulators too much for simple tasks. _____________________________ Posted through www.DSPRelated.com
Reply by ●June 21, 20132013-06-21
Tauno Voipio wrote:> On 21.6.13 4:43 , Richard Owlett wrote: >> In a sense this is a "homework" question. >> The catch is it is homework from 50 years ago in a first >> semester of DC >> circuits ;/ >> >> The immediate problem is quite simple. It is a 2 port network of 6 >> components with 2 internal nodes. It is driven by a ideal >> voltage source >> and I want to solve for the open circuit output voltage. It >> actually >> would have been suitable homework. >> >> Pointer to suitable refresher site please. >> P.S. I do expect to say *DUH* when recalling how to solve. > > > The canonical way is to write the loop equations, using Ohm's and > Kirchhoff's rules: > - the voltage over a resistor is resistance multiplied by current, > - the sum of currents in any node is zero, > - the sum of voltages around a loop is zero. > > There will be a linear equation group to solve, but it may be > tedious.Chuckle. What I need is the refresher in writing down those linear equations. I can write lots of valid equations. I've got myself trapped in an infinite loop mentally where the number of equations <> number of unknowns ;) That's why I asked for a pointer to instructional material.> > Depending on your circuit, it may be possible to simplify it > using the wye-delta transform and Thevenin's or Norton's theorems. >Never thought about wye-delta in DC terms. Only place I ever ran into it was in 3-phase power. In this case the wye representation would be really nice as the impedance of each leg would be inherently equal. Worth some thought. If you can't solve one problem, solve a different one.
Reply by ●June 21, 20132013-06-21
dszabo wrote:>> On 21.6.13 4:43 , Richard Owlett wrote: >>> In a sense this is a "homework" question. >>> The catch is it is homework from 50 years ago in a first semester of DC >>> circuits ;/ >>> >>> The immediate problem is quite simple. It is a 2 port network of 6 >>> components with 2 internal nodes. It is driven by a ideal voltage > source >>> and I want to solve for the open circuit output voltage. It actually >>> would have been suitable homework. >>> >>> Pointer to suitable refresher site please. >>> P.S. I do expect to say *DUH* when recalling how to solve. >> >> >> The canonical way is to write the loop equations, using Ohm's and >> Kirchhoff's rules: >> - the voltage over a resistor is resistance multiplied by current, >> - the sum of currents in any node is zero, >> - the sum of voltages around a loop is zero. >> >> There will be a linear equation group to solve, but it may be tedious. >> >> Depending on your circuit, it may be possible to simplify it >> using the wye-delta transform and Thevenin's or Norton's theorems. >> >> -- >> >> Tauno Voipio >> > > Circuit simulators are super good at solving 'tedious' networks. >One should not use canned solutions when not able to solve problem the tedious way. I speak from decades of experience.
Reply by ●June 21, 20132013-06-21
Richard Owlett <rowlett@pcnetinc.com> writes:> dszabo wrote: >>> On 21.6.13 4:43 , Richard Owlett wrote: >>>> In a sense this is a "homework" question. >>>> The catch is it is homework from 50 years ago in a first semester of DC >>>> circuits ;/ >>>> >>>> The immediate problem is quite simple. It is a 2 port network of 6 >>>> components with 2 internal nodes. It is driven by a ideal voltage >> source >>>> and I want to solve for the open circuit output voltage. It actually >>>> would have been suitable homework. >>>> >>>> Pointer to suitable refresher site please. >>>> P.S. I do expect to say *DUH* when recalling how to solve. >>> >>> >>> The canonical way is to write the loop equations, using Ohm's and >>> Kirchhoff's rules: >>> - the voltage over a resistor is resistance multiplied by current, >>> - the sum of currents in any node is zero, >>> - the sum of voltages around a loop is zero. >>> >>> There will be a linear equation group to solve, but it may be tedious. >>> >>> Depending on your circuit, it may be possible to simplify it >>> using the wye-delta transform and Thevenin's or Norton's theorems. >>> >>> -- >>> >>> Tauno Voipio >>> >> >> Circuit simulators are super good at solving 'tedious' networks. >> > > One should not use canned solutions when not able to solve problem the > tedious way. I speak from decades of experience.I agree 1000 percent with you, Richard. That's like telling a 1st-grader, "calculators are super good at performing 2-digit addition!" -- Randy Yates Digital Signal Labs http://www.digitalsignallabs.com
Reply by ●June 21, 20132013-06-21
>dszabo wrote: >>> On 21.6.13 4:43 , Richard Owlett wrote: >>>> In a sense this is a "homework" question. >>>> The catch is it is homework from 50 years ago in a first semester ofDC>>>> circuits ;/ >>>> >>>> The immediate problem is quite simple. It is a 2 port network of 6 >>>> components with 2 internal nodes. It is driven by a ideal voltage >> source >>>> and I want to solve for the open circuit output voltage. It actually >>>> would have been suitable homework. >>>> >>>> Pointer to suitable refresher site please. >>>> P.S. I do expect to say *DUH* when recalling how to solve. >>> >>> >>> The canonical way is to write the loop equations, using Ohm's and >>> Kirchhoff's rules: >>> - the voltage over a resistor is resistance multiplied by current, >>> - the sum of currents in any node is zero, >>> - the sum of voltages around a loop is zero. >>> >>> There will be a linear equation group to solve, but it may be tedious. >>> >>> Depending on your circuit, it may be possible to simplify it >>> using the wye-delta transform and Thevenin's or Norton's theorems. >>> >>> -- >>> >>> Tauno Voipio >>> >> >> Circuit simulators are super good at solving 'tedious' networks. >> > >One should not use canned solutions when not able to solve >problem the tedious way. I speak from decades of experience. > >A moderately complex circuit analysis may involve assumptions. I would require a simulation or physical measurement (or both) of such a network to validate those assumptions before commiting to component values. Measure twice, cut once. _____________________________ Posted through www.DSPRelated.com
Reply by ●June 21, 20132013-06-21
On Fri, 21 Jun 2013 17:55:06 +0300, Tauno Voipio wrote:> On 21.6.13 4:43 , Richard Owlett wrote: >> In a sense this is a "homework" question. The catch is it is homework >> from 50 years ago in a first semester of DC circuits ;/ >> >> The immediate problem is quite simple. It is a 2 port network of 6 >> components with 2 internal nodes. It is driven by a ideal voltage >> source and I want to solve for the open circuit output voltage. It >> actually would have been suitable homework. >> >> Pointer to suitable refresher site please. P.S. I do expect to say >> *DUH* when recalling how to solve. > > > The canonical way is to write the loop equations, using Ohm's and > Kirchhoff's rules: > - the voltage over a resistor is resistance multiplied by current, - > the sum of currents in any node is zero, - the sum of voltages around > a loop is zero. > > There will be a linear equation group to solve, but it may be tedious. > > Depending on your circuit, it may be possible to simplify it using the > wye-delta transform and Thevenin's or Norton's theorems.I can never keep track of loops. I find nodal equations to be much less confusing. I'm not sure where to send you, Richard -- I have my book from Sophomore circuits around here somewhere, but I never need it! Here it is verbally: Assign a voltage to each undetermined node (v1, v2, etc.). If you know all the node voltages, you can write out the currents in each leg (it works for AC as well as DC). Each leg current will be the conductance in that leg times the voltage difference between the two nodes that the leg runs between. You know that the current at each node sums to zero (Kirchoff's Current Law). So you can easily write an equation for each node. Now, solve the resulting linear algebra problem (I use Maxima if I want to do this symbolically, Scilab if numerically. Masochism is instructive, but one must have limits). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Reply by ●June 21, 20132013-06-21
jacobfenton wrote:>> In a sense this is a "homework" question. >> The catch is it is homework from 50 years ago in a first semester >> of DC circuits ;/ >> >> The immediate problem is quite simple. It is a 2 port network of >> 6 components with 2 internal nodes. It is driven by a ideal >> voltage source and I want to solve for the open circuit output >> voltage. It actually would have been suitable homework. >> >> Pointer to suitable refresher site please. >> P.S. I do expect to say *DUH* when recalling how to solve. >> >> >> >> > > http://en.wikiversity.org/wiki/Electric_Circuit_Analysis > > Try that website, I have not verified its contents, but looks decent.The stated goal of lessons 7 and 8 is to be able to solve my problem. Thanks.> > Simplify impedances as much as possible (parallel, series combos) then do > loop/node equations as necessary. > > Long hand is fun sometimes, instead of using simulators. I am starting to > feel people rely on simulators too much for simple tasks. >It's not always "fun". But it can keep you from some silly misteks.
