Constant illumination control system

An illumination level control system for maintaining a predetermined level of total illumination in an area of controlled lighting comprising:

• a. lighting means for generating artificial illumination in the area of controlled lighting;
• b. a first solid state switch coupled between said lighting means and a source of alternating current power;
• said first solid state switch having a gate input and being operable by a gating signal applied to the gate input to electrically connect or disconnect said lighting means and the source of alternating current power;
• c. monitoring means for monitoring the level of illumination in the area of controlled lighting and generating an illumination level voltage corresponding thereto;
• d. comparing means coupled to said monitoring means for comparing the illumination level voltage from said monitoring means with a reference voltage and generating an output difference voltage corresponding to the difference between the output of said monitoring means and the reference voltage;
• e. a monostable multivibrator circuit coupled to the gate input to said first solid state switch for generating the gating signal operable to switch said first solid state switch into and out of the conducting state;
• f. a timing circuit coupled between said comparing means and said monostable multivibrator circuit operable to establish the external time constant of said monostable multivibrator circuit;
• g. a triggering circuit coupled between said monostable multivibrator and the source of alternating current power for triggering said monostable multivibrator;
• h. said timing circuit in combination with said triggering circuit being operable to control the gating signal from said monostable multivibrator and, thereby, regulate the amount of power supplied to said lighting means.