diff --git a/README.md b/README.md
index 404daba..52094b5 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@ A tiny tank cooler.
 Used components:
 ----------------
 
-Arduino nano
+Arduino nano (old bootloader)
 PC fan 120mm 5V
 PWM D4184 MOS breakout board
 USB-C connector
@@ -28,3 +28,6 @@ D9       <-> PWM Pin of the breakout board
 A4       <-> SCL pin of BMP280 breakout board
 A5       <-> SDA pin of BMP280 breakout board
 
+PWM board load <-> PC fan (+)
+PWM board GNC  <-> PC fan (-)
+