LED circuit diagram - LED strobe has independent delay and duration The circuit applies a 5V pulse, the main clock, to diode D 1 and capacitor C 1 to form a peak-hold circuit. C 1 then discharges at a rate that P 1 sets. Michael C Page, Chelmsford, MA, USA High-brightness LEDs, with independent delay and duration, find use in a visual-inspection application. The circuit is not complex, but it saved the day in an application involving visual inspection of the spray pattern of fuel injectors for quality and consistency.