diff --git a/README.md b/README.md
index adae17a..1ac4966 100644
--- a/README.md
+++ b/README.md
@@ -6,3 +6,5 @@ The code is based on some personal preferences:
 * Once presssed, you have to wait 5 seconds (delayed_off) AFTER releasing the button, before the bell will ring again. Pressing the button within 5 seconds will only reset the timer without ringing the bell.
 
 In Home Assistant you'll need to create a boolean, which in my code is named "input_boolean.mute_doorbell". This piece of code is shown in home-assistant_input_boolean
+# The hardware
+The hardware is quite easy. It's based on a Wemos D1 mini. That's powered on the 5V pin. The doorbell is connected between the 3.3V and the D2 connector. There is a resistor between ground and D2 (this can be anything between 1K and 100K, I've used a 1K here) for a pull-down to ground.