Small Aircraft; Low Wing; 1 Eng; Retractable Gear
Flight Crew Instrument
Flight Crew Last 90 Days 40; Flight Crew Total 4257; Flight Crew Type 82
Situational Awareness
Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Human Factors
Cleared for the RNAV 05 Approach.  Instructed to cross FOVOJ at or above 2;500 feet.  Set Altitude on A/P for DH.  Aircraft started down and action was taken at 1;300 feet MSL.  ATC called me as well. It would not have occurred had I done a proper instrument scan.
Light aircraft pilot reported receiving a low altitude alert from ATC after descending below cleared altitude on approach to UGN airport.