Strobe Light Circuit
Posted on Jan 2, 2013 9738
This strobe light operates from standard 120-Vac power. Rl limits the amount of current applied to the voltage doubler stage, which is comprised of CI, C2, C3, Dl, D2, C4, C5, and C6. Capacitors CI, C2, and C3 are connected in parallel and form a capacitance of 30 at 160 V. Capacitors C4, C5, and C6 are connected in series and form an equivalent capacitor of about 53 at 480 V. Diodes Dl and D2 not only rectify the ac voltage, but also complete the voltage doubler stage, which converts the incoming 120 Vac to the appropriately 300 V that are required by the xenon strobe tube.
The next stage of the circuit is the neon relaxation oscillator and trigger stage. This stage is made up of R2, PI, C7, LI, Ql, Tl, and T2. As the storage capacitor (made up of C4, C5, and C6) reaches its full-capacity charge, the voltage divider (made up of R2 and PI) applies voltage to capacitor C7. As C7 charges up, it reaches a threshold voltage level, SCR Ql. When Ql has a positive pulse on its gate, it fires (causes a short from anode to cathode). That firing action discharges most of the energy stored in C7 into trigger transformers Tl and T2 (which have secondaries connected in scries to developer 8 kV). The frequency of the 8-kV pulses is determined by the setting of PI and the value of CT Because C7 is a fixed capacitor, only the setting of PI adjusts the flash rate in this circuit. As soon as an 8-kV pulse is applied from the secondary of T2 (trigger wire) to the trigger lead of FT1, it discharges storage capacitors C4, C5, and C6, which causes it to ionize (flash). The cycle then repeats itself until the power is removed from the circuit board by turning off SI or removing the line cord.