TWR Lighting E-2/3DB - Timing Circuit; Trigger Circuit

E-2/3DB CONTROLLER
E:\Documents and Settings\Administrator\Local Settings\Temporary Internet Files\OLK3\E2-3DB.doc
Rev. 01/13/00; Rev. 07/2000 o2L/H
Rev. 10/2000 (dwgs. 100239, 601, 601-01, 601-02, H02-258, 100031, 279L, 274S, 100089)
Rev. 06/21/00 (Reformatted Text; Revised Pg. 3 (2.4.1, 20 amp to 30 amp)
Pg. 13
The flashtube contains a gas called Xenon. When the high voltage energy
in the storage capacitors is connected to the flashtube, nothing will happen
since Xenon in its natural state is not a conductor of electricity. However,
when a very short duration high voltage pulse is impressed on the trigger
element of the tube (via the power supply and trigger transformers T4, T5,
T6, T7, T8, and T9) the Xenon gas is ionized and thereby becomes a good
conductor of electricity. This allows the electrical energy in the storage
capacitors to discharge rapidly through the flashtube, which converts this
energy to light energy and heat energy. When the voltage stored in the
capacitors discharges to a low level, the Xenon gas can no longer sustain
conduction and since the short trigger pulse is gone by this time, it de-
ionizes returning to its non-conducting state until another trigger pulse
arrives to repeat the process. Meanwhile, the storage capacitor is being re-
charged by the transformer and the high voltage rectifiers.
3.3 TIMING CIRCUIT
The timing circuit is contained entirely on printed circuit board #1. The
timing circuit has its own power supply. This circuit converts the AC voltage
to approximately 12V DC, which is used to supply all of the components in
this circuit. It uses this low voltage DC to generate pulses that control the
flash rate of the flashtube. It actually generates two (2) groups of pulses.
The first is a pulse approximately once every 1.2 seconds to operate the
flashtube during daylight hours. The second is a burst at 100Hz to elongate
the apparent flash during the night time hours at reduced flash energy.
3.4 TRIGGER CIRCUIT
The trigger circuit is supplied by transformer T1 secondary windings. The
250V AC is converted to DC, which is stored in a storage capacitor much like
the action of the high voltage circuit. The main difference is that the storage
capacitor is much smaller. The trigger circuit receives the pulses generated
by the timing circuit. It releases its stored energy with each pulse and
delivers it to the flashtube's trigger element to initiate each flash.