Add arduino sketch

kbdswitch.ino

@@ -0,0 +1,21 @@
+#define LED_PIN 1     // LED inside the pushbutton.
+#define RELAY_PIN 3   // Pin, the relay (transistor) is connected to.
+#define SWITCH_PIN 2  // The actual pushbutton.
+
+bool relay_on = 0;
+uint16_t debounce_time = 450;   // In ms. Adjust, if desired.
+
+void setup() {
+  pinMode(LED_PIN, OUTPUT);  
+  pinMode(RELAY_PIN, OUTPUT);
+  pinMode(SWITCH_PIN, INPUT_PULLUP);  // Saves some space on the PCB.
+}
+
+void loop() {
+  if (digitalRead(SWITCH_PIN) == LOW) {
+    relay_on ^= 1;  // Toggle the relay state.
+    digitalWrite(RELAY_PIN, relay_on);
+    digitalWrite(LED_PIN, relay_on);  // One could switch the LED state around if desired.
+    delay(debounce_time); // Simple switch debouncing.
+  }
+}