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Re: Spice Question

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Joe Riel <joer@san.rr.com> writes:

> "Thomas D. Dean" <tomdean@speakeasy.org> writes:
>
>> How do I form, solve
>>
>> ## syrup example for the problem posed on the maxima mailing list
>> ## by Rupert Swarbrick rswarbrick@gmail.com
>> ## creating a shunt to measure current from a power supply in decade
>> ## steps.
>> ## the maxima solution is:
>> ##  (%o49) [r1 =   0.04000003980823639,r2 =   0.400003980860735,
>> ##          r3 =   4.000398123173552,  r4 =   40.03984945656259,
>> ##          r5 = 404.0224806732696,    r6 = 4444.219040588743]
>> restart; with(Syrup);
>> r_isol:=100000;
>> ckt:="*Shunt by Rupert Swarbrick \n\
>> V 1 2 1 \n\
>> R1 1 2 \n\
>> Ra 1 3 r_isol \n\
>> Rb 2 4 r_isol \n\
>> R2a  3 21 r_isol \n\
>> R2  21 22 \n\
>> R2b 22  4 r_isol \n\
>> R3a  3 31 r_isol \n\
>> R3  31 32 \n\
>> R3b 32  4 r_isol \n\
>> R4a  3 41 r_isol \n\
>> R4  41 42 \n\
>> R4b 42  4 r_isol \n\
>> R5a  3 51 r_isol \n\
>> R5  51 52 \n\
>> R5b 52  4 r_isol \n\
>> R6a  3 61 r_isol \n\
>> R6  61 62 \n\
>> R6b 62  4 r_isol \n\
>> .end";
>>
>> I tried using a subckt for the R2..R6 parts.
>> ##
>> ## X2 3 4 net(Rx=R2) \n\
>> ## X3 3 4 net(Rx=R3) \n\
>> ## X4 3 4 net(Rx=R4) \n\
>> ## X5 3 4 net(Rx=R5) \n\
>> ## X6 3 4 net(Rx=R6) \n\
>> ## \n
>> ## .subckt net p n \n\
>> ## R1 p a r_isol \n\
>> ## R a b Rx \n\
>> ## R2 b n r_isol \n\
>> ## .ends net \n\
>>
>> Is this correct, other than being commented out?
>>
>> Tom Dean
>
> As with any Spice deck, you need to assign ground (node 0).
> Preferable is to change, say, node 1 to node 0. 
> Or add a short between 0 and 1.   Your subcircuit looks okay,
> but I haven't tried it.

Here's what I did:

restart; with(Syrup);
r_isol:=100000;
ckt :=
"*Shunt by Rupert Swarbrick
V 0 2 1
R1 0 2
Ra 0 3 r_isol
Rb 2 4 r_isol
R2a  3 21 r_isol
R2  21 22
R2b 22  4 r_isol
R3a  3 31 r_isol
R3  31 32
R3b 32  4 r_isol
R4a  3 41 r_isol
R4  41 42
R4b 42  4 r_isol
R5a  3 51 r_isol
R5  51 52
R5b 52  4 r_isol
R6a  3 61 r_isol
R6  61 62
R6b 62  4 r_isol
.end":

sol := Solve(ckt,dc);

That returns a solution for the node voltages in terms of the
symbolic R1, R2, etc.  Not sure what you intend afterwards.

-- 
Joe Riel

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Spice Question "Thomas D. Dean" <tomdean@speakeasy.org> - 2014-08-30 14:35 -0700
  Re: Spice Question Joe Riel <joer@san.rr.com> - 2014-08-30 17:15 -0700
    Re: Spice Question Joe Riel <joer@san.rr.com> - 2014-08-30 17:18 -0700
    Re: Spice Question "Thomas D. Dean" <tomdean@speakeasy.org> - 2014-08-30 23:44 -0700
      Re: Spice Question Joe Riel <joer@san.rr.com> - 2014-08-31 08:02 -0700
        Re: Spice Question "Thomas D. Dean" <tomdean@speakeasy.org> - 2014-09-01 21:22 -0700

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