Fingerprint scanner not recognising fingers

摘要

I recently built the Fingerprint Scanner Access Controller project from the November 2015 issue. I wanted to use it with a 12V DC relay to activate the manual open button of my roller door from outside the front driveway. Right from the start things did not go smoothly. All the wiring went OK but trying to register any of my fingerprints took an eternity - at least half a dozen attempts per finger and I tried the middle and pointer fingers of each hand, all moistened as per instructions. When they did eventually register, not one of them would be recognised by the scanner and allow entry.