Xenon-flash-trigger

Description: This circuit is utilized for remote photographic flash units that synchronize with the flash attached to the camera. It is designed to connect to the trigger cord or hot shoe of a commercial portable flash unit, allowing the unit to be triggered by the light emitted from the camera's flash. This setup enables remote operation without requiring wires or cables between the various components. To prevent an inadvertent flash upon connection, the flash trigger unit should be connected to the slave flash before powering on the flash.

The L14C1 phototransistor features a wide, nearly cosine viewing angle, making alignment non-critical. For applications requiring a more sensitive and directional remote trigger, the circuit can be adapted by using an L14G2 lensed phototransistor as the sensor. This lensed transistor offers a viewing angle of approximately 10 degrees, resulting in over a tenfold increase in light sensitivity (with a threefold range improvement). It is important to note that the phototransistor is configured in a self-biasing circuit that is relatively unaffected by slow-changing ambient light, while still discharging the 0.01 µF capacitor into the gate of the C106D upon exposure to a photo flash. For a more compact design, the C106D can be substituted with a C205D, provided that the duty cycle is appropriately reduced.

The circuit operates by utilizing the phototransistor to detect the flash from the primary camera-mounted unit. When the camera's flash is triggered, the light from this flash illuminates the phototransistor, which then activates the connected slave flash unit. The self-biasing nature of the circuit ensures that it remains stable in varying light conditions, making it an effective solution for photographers seeking to achieve synchronized lighting without the clutter of physical connections. The choice of phototransistor can significantly influence the performance and sensitivity of the setup, allowing for customization based on specific photographic needs.

In summary, this circuit provides a reliable and flexible means of achieving remote flash synchronization, enhancing the versatility of photographic lighting setups. The ability to modify components for sensitivity and size further contributes to its utility in various photographic scenarios.This circuit is used for remote photographic flash units that flash at the~ame time as the flash attached to the camera. This circuit is designed to the trigger cord or hot shoe connection of a commercial portable flash unit and triggers the unit from the light produced by the light of the flash unit attached to the camera.

This provides remoteoperation without the need for wires or cables between the various units. The flash trigger unit should be connected to the slave flash before turning the flash on to prevent a d VIdt triggered flash on connection. The L14C1 phototransistor has a wide, almost cosine viewing angle, so aligmnent is not critical. If a very sensitive, more directional remote trigger unit is desired, the circuit can be modified using an L14G2 lensed phototransistor as the sensor. The lens on this transistor provides a viewing angle of approximately 10° and gives over a 10 to 1 improvement in light sensitivity (3 to 1 range improvement).

Note that the phototransistor is connected in a self-biasing circuit which is relatively insensitive to slow-changing ambient light, and yet discharges the 0.01-I"F capacitor into the Cl06D gate when illuminated by a photo flash. For a physically smaller size, the C106D can be replaced by a C205D, if the duty cycle is reduced appropriately.