add capacitor series resistance (sharpie7#937, sharpie7#321)

remove hated "capacitor loop with no resistance" error (sharpie7#845, sharpie7#634)

src/com/lushprojects/circuitjs1/client/CapacitorElm.java

@@ -23,8 +23,9 @@
 
 class CapacitorElm extends CircuitElm {
 	double capacitance;
-	double compResistance, voltdiff;
+	double compResistance, voltdiff, seriesResistance;
 	double initialVoltage;
+	int capNode2;
 	Point plate1[], plate2[];
 	public static final int FLAG_BACK_EULER = 2;
 	public CapacitorElm(int xx, int yy) {
@@ -40,6 +41,7 @@ public CapacitorElm(int xa, int ya, int xb, int yb, int f,
 	    initialVoltage = 1e-3;
 	    try {
 		initialVoltage = new Double(st.nextToken()).doubleValue();
+		seriesResistance = new Double(st.nextToken()).doubleValue();
 	    } catch (Exception e) {}
 	}
 	boolean isTrapezoidal() { return (flags & FLAG_BACK_EULER) == 0; }
@@ -56,7 +58,7 @@ void shorted() {
 	}
 	int getDumpType() { return 'c'; }
 	String dump() {
-	    return super.dump() + " " + capacitance + " " + voltdiff + " " + initialVoltage;
+	    return super.dump() + " " + capacitance + " " + voltdiff + " " + initialVoltage + " " + seriesResistance;
 	}
 
 	// used for PolarCapacitorElm
@@ -115,9 +117,16 @@ void stamp() {
 		// when finding DC operating point, replace cap with a 100M resistor
 		sim.stampResistor(nodes[0], nodes[1], 1e8);
 		curSourceValue = 0;
+		capNode2 = 1;
 		return;
 	    }
 
+	    // The capacitor model is between nodes 0 and capNode2.  For an
+	    // ideal capacitor, capNode2 is node 1.  If series resistance, capNode2 = 2
+	    // and we place a resistor between nodes 2 and 1.
+	    // 2 is an internal node, 0 and 1 are the capacitor terminals.
+	    capNode2 = (seriesResistance > 0) ? 2 : 1;
+
 	    // capacitor companion model using trapezoidal approximation
 	    // (Norton equivalent) consists of a current source in
 	    // parallel with a resistor.  Trapezoidal is more accurate
@@ -127,9 +136,11 @@ void stamp() {
 		compResistance = sim.timeStep/(2*capacitance);
 	    else
 		compResistance = sim.timeStep/capacitance;
-	    sim.stampResistor(nodes[0], nodes[1], compResistance);
+	    sim.stampResistor(nodes[0], nodes[capNode2], compResistance);
 	    sim.stampRightSide(nodes[0]);
-	    sim.stampRightSide(nodes[1]);
+	    sim.stampRightSide(nodes[capNode2]);
+	    if (seriesResistance > 0)
+		sim.stampResistor(nodes[1], nodes[2], seriesResistance);
 	}
 	void startIteration() {
 	    if (isTrapezoidal())
@@ -139,7 +150,7 @@ void startIteration() {
 	}
 
 	void stepFinished() {
-	    voltdiff = volts[0]-volts[1];
+	    voltdiff = volts[0]-volts[capNode2];
 	    calculateCurrent();
 	}
 
@@ -151,7 +162,7 @@ void setNodeVoltage(int n, double c) {
 	}	
 
 	void calculateCurrent() {
-	    double voltdiff = volts[0] - volts[1];
+	    double voltdiff = volts[0] - volts[capNode2];
 	    if (sim.dcAnalysisFlag) {
 		current = voltdiff/1e8;
 		return;
@@ -166,8 +177,9 @@ void calculateCurrent() {
 	void doStep() {
 	    if (sim.dcAnalysisFlag)
 		return;
-	    sim.stampCurrentSource(nodes[0], nodes[1], curSourceValue);
+	    sim.stampCurrentSource(nodes[0], nodes[capNode2], curSourceValue);
  	}
+	int getInternalNodeCount() { return (!sim.dcAnalysisFlag && seriesResistance > 0) ? 1 : 0; }
 	void getInfo(String arr[]) {
 	    arr[0] = "capacitor";
 	    getBasicInfo(arr);
@@ -190,6 +202,8 @@ public EditInfo getEditInfo(int n) {
 	    }
 	    if (n == 2)
 		return new EditInfo("Initial Voltage (on Reset)", initialVoltage);
+	    if (n == 3)
+		return new EditInfo("Series Resistance (0 = infinite)", seriesResistance);
 	    // if you add more things here, check PolarCapacitorElm
 	    return null;
 	}
@@ -204,8 +218,13 @@ public void setEditValue(int n, EditInfo ei) {
 	    }
 	    if (n == 2)
 		initialVoltage = ei.value;
+	    if (n == 3)
+		seriesResistance = ei.value;
 	}
 	int getShortcut() { return 'c'; }
 	public double getCapacitance() { return capacitance; }
+	public double getSeriesResistance() { return seriesResistance; }
 	public void setCapacitance(double c) { capacitance = c; }
+	public void setSeriesResistance(double c) { seriesResistance = c; }
+	public boolean isIdealCapacitor() { return (seriesResistance == 0); }
     }

src/com/lushprojects/circuitjs1/client/CirSim.java

@@ -2378,21 +2378,20 @@ boolean validateCircuit() {
 	    }
 
 	    // look for shorted caps, or caps w/ voltage but no R
-	    if (ce instanceof CapacitorElm) {
+	    if (ce.isIdealCapacitor()) {
 		FindPathInfo fpi = new FindPathInfo(FindPathInfo.SHORT, ce,
 						    ce.getNode(1));
 		if (fpi.findPath(ce.getNode(0))) {
 		    console(ce + " shorted");
 		    ((CapacitorElm) ce).shorted();
 		} else {
-		    // a capacitor loop used to cause a matrix error. but we changed the capacitor model
-		    // so it works fine now. The only issue is if a capacitor is added in parallel with
-		    // another capacitor with a nonzero voltage; in that case we will get oscillation unless
-		    // we reset both capacitors to have the same voltage. Rather than check for that, we just
-		    // give an error.
 		    fpi = new FindPathInfo(FindPathInfo.CAP_V, ce, ce.getNode(1));
 		    if (fpi.findPath(ce.getNode(0))) {
-			stop("Capacitor loop with no resistance!", ce);
+			// loop of ideal capacitors; set a small series resistance to avoid
+			// oscillation in case one of them has voltage on it
+			((CapacitorElm) ce).setSeriesResistance(.1);
+
+			// return false to re-stamp the circuit
 			return false;
 		    }
 		}
@@ -2477,10 +2476,20 @@ boolean preStampCircuit() {
 
     // stamp the matrix, meaning populate the matrix as required to simulate the circuit (for all linear elements, at least)
     void stampCircuit() {
-	if (!preStampCircuit())
+	int i;
+
+	// preStampCircuit returns false if there's an error.  It can return false if we have capacitor loops
+	// but we just need to try again in that case.  Try again 10 times to avoid infinite loop.
+	for (i = 0; i != 10; i++)
+	    if (preStampCircuit() || stopMessage != null)
+		break;
+	if (stopMessage != null)
+	    return;
+	if (i == 10) {
+	    stop("failed to stamp circuit", null);
 	    return;
+	}
 
-	int i;
 	int matrixSize = nodeList.size()-1 + voltageSourceCount;
 	circuitMatrix = new double[matrixSize][matrixSize];
 	circuitRightSide = new double[matrixSize];
@@ -2772,7 +2781,7 @@ boolean checkElm(int n1, CircuitElm ce) {
 		    return false;
 		if (type == CAP_V) {
 		    // checking for capacitor/voltage source loops
-		    if (!(ce.isWireEquivalent() || ce instanceof CapacitorElm || ce instanceof VoltageElm))
+		    if (!(ce.isWireEquivalent() || ce.isIdealCapacitor() || ce instanceof VoltageElm))
 			return false;
 		}
 		if (n1 == 0) {

src/com/lushprojects/circuitjs1/client/CircuitElm.java

@@ -1069,6 +1069,8 @@ public void setEditValue(int n, EditInfo ei) {}
     // is this a wire we can remove?
     boolean isRemovableWire() { return false; }
 
+    boolean isIdealCapacitor() { return false; }
+
     boolean canViewInScope() { return getPostCount() <= 2; }
     boolean comparePair(int x1, int x2, int y1, int y2) {
 	return ((x1 == y1 && x2 == y2) || (x1 == y2 && x2 == y1));

src/com/lushprojects/circuitjs1/client/PolarCapacitorElm.java

@@ -49,12 +49,12 @@ void getInfo(String arr[]) {
 	    arr[0] = "capacitor (polarized)";
 	}
 	public EditInfo getEditInfo(int n) {
-	    if (n == 3)
+	    if (n == 4)
 		return new EditInfo("Max Reverse Voltage", maxNegativeVoltage, 0, 0);
 	    return super.getEditInfo(n);
 	}
 	public void setEditValue(int n, EditInfo ei) {
-	    if (n == 3 && ei.value >= 0)
+	    if (n == 4 && ei.value >= 0)
 		maxNegativeVoltage = ei.value;
 	    super.setEditValue(n, ei);
 	}