diff --git a/limits.py b/limits.py
new file mode 100644
index 0000000..0d39b60
--- /dev/null
+++ b/limits.py
@@ -0,0 +1,28 @@
+import time
+import sys
+import RPi.GPIO as GPIO
+
+GPIO.setmode(GPIO.BCM)
+
+GPIO.setup(19, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+GPIO.setup(20, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+GPIO.setup(21, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+
+# 1 = optical path blocked, 0 = open
+
+def test():
+    while True:
+        try:
+            print(
+                'GPIO19:', GPIO.input(19),
+                'GPIO20:', GPIO.input(20),
+                'GPIO21:', GPIO.input(21),
+            )
+
+            time.sleep(1)
+        except KeyboardInterrupt as e:
+            sys.exit()
+
+
+if __name__ == '__main__':
+    test()