# Tool for composable circuit simulation?

**URL:** https://discourse.julialang.org/t/tool-for-composable-circuit-simulation/103449
**Category:** Modelling & Simulations
**Tags:** question, modelingtoolkit
**Created:** [September 1, 2023, 4:18pm UTC](https://discourse.julialang.org/t/tool-for-composable-circuit-simulation/103449 "2023-09-01T16:18:27Z")
**Posts on this page:** 1
**Showing post:** 7

<div class="post-metadata">

### Author: ![hacklint](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/hacklint/32/25568_2.png) [@hacklint](https://discourse.julialang.org/u/hacklint)
#### Post date: [September 8, 2023, 2:51pm UTC](https://discourse.julialang.org/t/tool-for-composable-circuit-simulation/103449/7 "2023-09-08T14:51:16Z")

</div>

Here is a seemingly working example.  
Moving the equations definition to before the parameter definition makes the ifelse evaluate OK.  
I guess that there are still problems left here…  
To go back to your question about how the switches are defined, I guess it would be better to be able to define the state (open/closed) with parameter when the ODAEProblem is defined? Not sure if that would work with the equations being defined as they are now though…  
Anyway, code below, laced with quite a few debug printouts in the IdealSwitch  
I realise the isequal(isClosed,True) is redundant at start, but it is needed (but failing)  
after the @parameter step.

```julia
using Revise
using ModelingToolkit
using ModelingToolkitStandardLibrary.Electrical
using ModelingToolkitStandardLibrary.Electrical: OnePort, Ground
using OrdinaryDiffEq
using Plots
using IfElse: ifelse

@parameters t

# No switch... need to define that.

@component function IdealSwitch(; name, isClosed=true)
    println("Creating switch, isClosed=$(isClosed)")
    println(" Before param assign: $(isClosed) -> t? $(isequal(isClosed,true)) -> f? $(isequal(isClosed, false))")
    println("typeof(isClosed): $(typeof(isClosed))")
    @named oneport = OnePort()
    @unpack v, i = oneport
    @variables closed # Dummy to include in eqs
    eqs = [ v ~ ifelse(isequal(isClosed, true), 0, v)
            i ~ ifelse(isequal(isClosed, true), i, 0)
            closed ~ isequal(isClosed, true)
    ]
    println(" eqs: $(eqs)")
    
    ps = @parameters isClosed = isClosed
    println("ps: $ps")

    # Original placement of eqs definition - ie _after_ params: here isequal always evaluate to false
    #eqs = [ v ~ ifelse(isequal(isClosed, true), 0, v)
    # i ~ ifelse(isequal(isClosed, true), i, 0)
    # closed ~ isequal(isClosed, true)
    #]
    #println(" eqs: $(eqs)")

    println("After param assign: $(isClosed) -> t? $(isequal(isClosed,true)) -> f? $(isequal(isClosed, false))")
    println(" typeof(isClosed): $(typeof(isClosed))")
    println(" Switch is $(ifelse(isequal(isClosed, true), "CLOSED", "OPEN"))")
    extend(ODESystem(eqs, t, [], ps; name = name), oneport)
end

@named s_closed = IdealSwitch(;isClosed=true)
# equations(s_closed)
# @named s_open = IdealSwitch(;isClosed=false)
# equations(s_open)

@component function ConstantVoltage(; name, V = 12.0)
    @named oneport = OnePort()
    @unpack v = oneport
    ps = @parameters V = V
    eqs = [
        V ~ v
    ]
    extend(ODESystem(eqs, t, [], ps; name = name), oneport)
end

@named vcc = ConstantVoltage()
@named resistor = Resistor(R=2)
@named switch = IdealSwitch(isClosed=true)
@named ground = Ground()

eqs = [
    connect(vcc.p, resistor.p)
    connect(resistor.n, switch.p)
    connect(vcc.n, switch.n, ground.g)]

@named switch_sys = ODESystem(eqs, t;
    systems = [vcc, resistor, switch, ground])
sys = structural_simplify(switch_sys)
prob = ODAEProblem(sys, [], (0, 10.0))
sol = solve(prob, Tsit5())

plot(sol, idxs = [resistor.v, resistor.i],
    title = "Switch Demonstration",
    labels = ["Resistor Voltage" "Resistor Current"])

```

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