diff --git a/light8/io.py b/light8/io.py
--- a/light8/io.py
+++ b/light8/io.py
@@ -2,6 +2,7 @@ from parport import *
 
 class ParportDMX:
     def __init__(self, dummy=1, dimmers=68):
+        self.dimmers = dimmers
         self.dummy = dummy
         if not dummy:
             getparport()
@@ -10,5 +11,5 @@ class ParportDMX:
         levels = list(levels) + [0]
         # if levels[14] > 0: levels[14] = 100 # non-dim
         outstart()
-        for p in range(1, dimmers + 2):
+        for p in range(1, self.dimmers + 2):
             outbyte(levels[p-1]*255 / 100)