For the 'Pushbutton to 12V', you have a note under it that says that for 24v you should increase R to 2200 Ohms. You don't however mention which resistor to increase as there are two. While to the more experienced it is obviuos which you mean, for those who are new to electronics, it is asking for trouble, as increasing the bottom one would result in 16.5V across the arduino.The other thing is that you may want to check your 'Encoder' circuit. As it is there is nothing in the circuit to generate a logic 1, unless you are using 0v logicOther than that, looking good.