XENON STROBE

Description: A two-transistor oscillator generates pulses at approximately 500 Hz to step up the voltage using a 300-mA filament transformer (T1, Radio Shack 273-1384) for charging storage capacitors C2 and C3, which are 250-V electrolytics. At the same time, capacitor C4 is charged through resistor R2. After allowing sufficient time for the capacitors to charge, switch S1 is activated to discharge C4 through the 272-1146 tube trigger transformer (T2), which steps up the voltage pulse to around 4000 V for ionizing the gas in the 272-1145 xenon flashtube (FT1). Capacitors C2 and C3 then discharge through the ionized gas, producing a brilliant flash of white light lasting only a few microseconds, suitable for photographing fast-moving objects. The circuit may require two cells in series for reliable operation.

The described circuit employs a two-transistor oscillator configuration to generate a frequency of approximately 500 Hz. This oscillator is crucial for driving a filament transformer (T1, Radio Shack 273-1384), which serves the dual purpose of stepping up the voltage and providing the necessary current to charge the electrolytic capacitors (C2 and C3) rated at 250 V. The charging process is facilitated by the oscillation of the transistors, producing a square wave output that energizes the transformer.

Simultaneously, the circuit includes a resistor (R2) that allows capacitor C4 to charge. The choice of resistor value is critical as it determines the charging time constant, impacting the overall performance of the circuit. Once the capacitors are sufficiently charged, activating switch S1 initiates the discharge of capacitor C4 through the tube trigger transformer (T2). This transformer amplifies the voltage pulse to approximately 4000 V, which is necessary for ionizing the gas within the xenon flashtube (FT1, model 272-1145).

When the gas is ionized, it allows for a rapid discharge of energy from capacitors C2 and C3, resulting in a bright flash of white light. This flash duration is extremely brief, typically lasting only a few microseconds, making it ideal for capturing images of high-speed movements in photography. The circuit's design may necessitate the use of two cells in series to ensure adequate voltage and current for reliable operation, particularly when triggering the flashtube and maintaining the oscillator's functionality. This design exemplifies a practical application of transistor technology in creating high-intensity light sources for specialized photographic needs.Two transistor oscillator generates pulses at about 500 Hz for step-up by 300-mA filament transformer T1 (Radio Shack 273-1384) to charge storage capacitors C2 and C3, which are 250-V electrolytics. Simultaneously, C4 is charged through R2. After allowing sufficient time for capacitors to charge, S1 is pressed to discharge C4 through 272-1146 flas

htube trigger transformer T2, which steps up voltage pulse to about 4000 V for ionizing gas in 272-1145 xenon flashtube FT1. C2 and C3 now discharge through ionized gas to produce brilliant flash of white light lasting only a few microseconds, as required for photography of objects moving at high speed.

Circuit may require two cells in series for reliable operation. -F. M. Mims, "Transistor Projects, Vol. 3, " Radio Shack, Fort Worth, TX, 1975, p 49-60.