diff --git a/src/main.cpp b/src/main.cpp
index a7fefc8..9c079af 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4,17 +4,23 @@
 
 #define DCC_IRQ_MICROSECONDS 29
 
+#if defined(ARDUINO_AVR_UNO)
+#define NUM_LOCOS_MAIN 20
+#else
+#define NUM_LOCOS_MAIN 50
+#endif
+
 ////////////////////////////////////////////////////////////////
 // Motor driver selection:
 // Comment out all but the two lines that you want to use
 
-// DCC* mainTrack = DCC::Create_WSM_SAMCommandStation_Main(50);
+// DCC* mainTrack = DCC::Create_WSM_SAMCommandStation_Main(NUM_LOCOS_MAIN);
 // DCC* progTrack = DCC::Create_WSM_SAMCommandStation_Prog(2);
 
-DCC* mainTrack = DCC::Create_Arduino_L298Shield_Main(50);
+DCC* mainTrack = DCC::Create_Arduino_L298Shield_Main(NUM_LOCOS_MAIN);
 DCC* progTrack = DCC::Create_Arduino_L298Shield_Prog(2);
     
-// DCC* mainTrack = DCC::Create_Pololu_MC33926Shield_Main(50);
+// DCC* mainTrack = DCC::Create_Pololu_MC33926Shield_Main(NUM_LOCOS_MAIN);
 // DCC* progTrack = DCC::Create_Pololu_MC33926Shield_Prog(2);
 
 ////////////////////////////////////////////////////////////////
@@ -34,7 +40,7 @@ void SERCOM4_Handler()
 void setup() {
     mainTrack->hdw.setup();
     progTrack->hdw.setup();
-    
+
     // TimerA is TCC0 on SAMD21, Timer1 on MEGA2560, and Timer1 on MEGA328
     // We will fire an interrupt every 29us to generate the signal on the track 
     TimerA.initialize();