add pulldown resistors to analog switches (#101)

pfalstad · Nov 11, 2024 · 1d86868 · 1d86868
1 parent f07a6c8
commit 1d86868
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Showing 2 changed files with 46 additions and 5 deletions.
diff --git a/src/com/lushprojects/circuitjs1/client/AnalogSwitch2Elm.java b/src/com/lushprojects/circuitjs1/client/AnalogSwitch2Elm.java
@@ -84,25 +84,38 @@ void stamp() {
 	sim.stampNonLinear(nodes[0]);
 	sim.stampNonLinear(nodes[1]);
 	sim.stampNonLinear(nodes[2]);
+	if (needsPulldown()) {
+	    sim.stampResistor(nodes[1], 0, r_off);
+	    sim.stampResistor(nodes[2], 0, r_off);
+	}
     }
     void doStep() {
 	open = (volts[3] < 2.5);
 	if ((flags & FLAG_INVERT) != 0)
 	    open = !open;
 	if (open) {
 	    sim.stampResistor(nodes[0], nodes[2], r_on);
-	    sim.stampResistor(nodes[0], nodes[1], r_off);
+	    if (!needsPulldown())
+	        sim.stampResistor(nodes[0], nodes[1], r_off);
 	} else {
 	    sim.stampResistor(nodes[0], nodes[1], r_on);
-	    sim.stampResistor(nodes[0], nodes[2], r_off);
+	    if (!needsPulldown())
+	        sim.stampResistor(nodes[0], nodes[2], r_off);
 	}
     }
 
     boolean getConnection(int n1, int n2) {
 	if (n1 == 3 || n2 == 3)
 	    return false;
+	if (needsPulldown())
+	    return comparePair(n1, n2, 0, open ? 2 : 1);
 	return true;
     }
+
+    boolean hasGroundConnection(int n) {
+	return needsPulldown() && n != 3;
+    }
+
     void getInfo(String arr[]) {
 	arr[0] = "analog switch (SPDT)";
 	arr[1] = "I = " + getCurrentDText(getCurrent());

diff --git a/src/com/lushprojects/circuitjs1/client/AnalogSwitchElm.java b/src/com/lushprojects/circuitjs1/client/AnalogSwitchElm.java
@@ -21,12 +21,14 @@
 
 class AnalogSwitchElm extends CircuitElm {
     final int FLAG_INVERT = 1;
+    final int FLAG_PULLDOWN = 2;
     double resistance, r_on, r_off;
     public AnalogSwitchElm(int xx, int yy) {
 	super(xx, yy);
 	r_on = 20;
 	r_off = 1e10;
 	noDiagonal = true;
+	flags |= FLAG_PULLDOWN;
     }
     public AnalogSwitchElm(int xa, int ya, int xb, int yb, int f,
 			   StringTokenizer st) {
@@ -77,22 +79,37 @@ void draw(Graphics g) {
 	drawPosts(g);
     }
     void calculateCurrent() {
-	current = (volts[0]-volts[1])/resistance;
+	if (needsPulldown() && open)
+	    current = 0;
+	else
+	    current = (volts[0]-volts[1])/resistance;
     }
 
     // we need this to be able to change the matrix for each step
     boolean nonLinear() { return true; }
 
+    boolean needsPulldown() { return (flags & FLAG_PULLDOWN) != 0; }
+
     void stamp() {
 	sim.stampNonLinear(nodes[0]);
 	sim.stampNonLinear(nodes[1]);
+	if (needsPulldown()) {
+	    // pulldown resistor on each side
+	    sim.stampResistor(nodes[0], 0, r_off);
+	    sim.stampResistor(nodes[1], 0, r_off);
+	}
     }
     void doStep() {
 	open = (volts[2] < 2.5);
 	if ((flags & FLAG_INVERT) != 0)
 	    open = !open;
-	resistance = (open) ? r_off : r_on;
-	sim.stampResistor(nodes[0], nodes[1], resistance);
+
+	// if pulldown flag is set, resistance is r_on.  Otherwise, no connection.
+	// if pulldown flag is unset, resistance is r_on for on, r_off for off.
+	if (!(needsPulldown() && open)) {
+	    resistance = (open) ? r_off : r_on;
+	    sim.stampResistor(nodes[0], nodes[1], resistance);
+	}
     }
     int getPostCount() { return 3; }
     Point getPost(int n) {
@@ -105,13 +122,19 @@ void getInfo(String arr[]) {
 	arr[3] = "I = " + getCurrentDText(getCurrent());
 	arr[4] = "Vc = " + getVoltageText(volts[2]);
     }
+
     // we have to just assume current will flow either way, even though that
     // might cause singular matrix errors
     boolean getConnection(int n1, int n2) {
 	if (n1 == 2 || n2 == 2)
 	    return false;
 	return true;
     }
+
+    boolean hasGroundConnection(int n1) { 
+	return needsPulldown() && (n1 < 2);
+    }
+
     public EditInfo getEditInfo(int n) {
 	if (n == 0) {
 	    EditInfo ei = new EditInfo("", 0, -1, -1);
@@ -123,6 +146,9 @@ public EditInfo getEditInfo(int n) {
 	    return new EditInfo("On Resistance (ohms)", r_on, 0, 0);
 	if (n == 2)
 	    return new EditInfo("Off Resistance (ohms)", r_off, 0, 0);
+	if (n == 3)
+	    return EditInfo.createCheckbox("Pulldown Resistor", needsPulldown());
+
 	return null;
     }
     public void setEditValue(int n, EditInfo ei) {
@@ -134,6 +160,8 @@ public void setEditValue(int n, EditInfo ei) {
 	    r_on = ei.value;
 	if (n == 2 && ei.value > 0)
 	    r_off = ei.value;
+	if (n == 3)
+	    flags = ei.changeFlag(flags, FLAG_PULLDOWN);
     }
 
     double getCurrentIntoNode(int n) {