diff --git a/pid/fan.hpp b/pid/fan.hpp
new file mode 100644
index 0000000..7792d04
--- /dev/null
+++ b/pid/fan.hpp
@@ -0,0 +1,9 @@
+
+#pragma once
+
+enum class FanSpeedDirection
+{
+    DOWN,
+    UP,
+    NEUTRAL, /* not sure this will ever happen, but for completeness. */
+};