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He used an example sketch included with the Arduino IDE. See Step-5 for details of how to find it. Cheers!
For anyone who is still thinking of building this and who has blinds that are not protected from over-tightening, you can use a small limit switch with a roller arm to ride along the top blade of the blind. Simply adjust the position of the switch so that when the blade is fully open the switch signals the arduino and your code can stop the motor. The same could be done to stop the motor when closing the blinds.