LED lighting unit

A lighting unit comprising:

• a light generating section comprising a plurality of groups of LEDs, each group emitting light of a different spectrum than said other groups, one of said groups including a plurality of LEDs;
• a light analysis section that generates a plurality of group intensity signals, each of said plurality of group intensity signals being based on the intensity of light generated by one of said groups;
• a controller that adjusts a current through each of said LEDs in response to said group intensity signals;
• a housing having a transparent window, said light generation section and said light analysis section being within said housing;
• a first communication interface that said controller utilizes to communicate with a device external to said lighting unit for receiving commands during the operation of said lighting unit;
• wherein said light analysis section also generates an ambient intensity signal based on the intensity of light in different spectral bands originating from a location outside of said housing;
• and
• wherein one of said groups comprises a spare LED that emits light in said spectrum of that group and wherein said controller detects an LED that is defective in that group and causes said spare LED to be connected in place of said defective LED.