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Assembly and Operating Instructions for Kits



The Launch Trigger



This image of the night launch of SpaceX AsiaSat 6 was captured by John Studwell of AmericaSpace. The camera was a Canon 50D, and the trigger was a Launch Trigger.

Photographing the launch of a rocket requires perseverance but not necessarily expensive equipment. Photographers set up their equipment in advance at a location specified by launch officials. The equipment must then be left unattended until the rocket is launched. In the event of a launch scrub, the equipment may be exposed to the weather for several days waiting for the next launch window. Both the camera and the trigger must have sufficient battery life and conserve what life they have in order to be ready to function when needed. A sound trigger is used to actuate the camera. Here are the requirements for the sound trigger.

  1. Unlike most applications using sound triggers, the trigger for a rocket launch must be relatively insensitive. Since the trigger must be set up for hours or days, one doesn't want environmental noise actuating the camera shutter and filling the memory card with useless photos prior to launch. The only triggering event of interest is the launch itself, and that produces such a high sound level that an insensitive trigger is optimal for the job.
  2. The sound trigger must have very low drain on its power source while in its quiescent state awaiting the launch.
  3. The sound trigger must wake up the camera at the beginning of the launch. (The camera is left in sleep mode up until the launch in order to conserve the camera battery.)

launch trigger schematic

The circuit diagram below shows a modified version of the SK2 trigger to meet the requirements of launch photography. This trigger is being used successfully by a number of photographers. The circuit diagram of the trigger is shown below.


In order to meet requirement #1 above, the sound trigger uses a piezoelectric disc as a sensing element. This element is only sensitive to loud and/or sharp sounds. Typical environmental noise won't set it off. Moreover, the trigger circuit itself has low sensitivity to minimize the chance of spurious discharges. A loud clap near the microphone is required to create a triggering event. Some control of the sensitivity is provided with the variable 1k resistor.


There is very little drain on the 9V battery that powers the circuit when the circuit is not responding to a triggering event. The sound trigger can be kept on for days and still be ready to function when needed. This meets requirement #2 above.


The trigger has a dual optocoupler output. One optocoupler wakes up the camera when a triggering event occurs. The other optocoupler opens the shutter. The shutter will continue to actuate as rapidly as the camera will allow as long as the sound level remains high enough. This meets requirement #3.


Figure 1 below shows the circuit built on a breadboard and housed in a plastic box by Alex Polimeni. He has used such breadboarded circuits for photographs such as these. These circuits even survived the Antares Orb-3 explosion.


As an example of the use of modern technology for creating a custom enclosure, Jay Patterson has used a 3D printer to create a compact housing for all the components Figures 2 and 3 show his creation.


Polimeni enclosure Patterson trigger enclosure Patterson enclosure
Figure 1. This compact and watertight enclosure was designed by Alex Polimeni to house a breadboard circuit. The front panel has an on-off switch and jacks for the microphone and the camera. Figures 2 and 3. Jay Patterson b uilt the launch circuit on a PC board and housed everything in an enclosure made with a 3d printer.

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