Here is the mechanics page of the new experimental prototype Digital Aurora Cam Controller. This device is designed to repeatedly press the Canon 10D's shutter button on the hand held remote autonomously, with the correct amount of force to just trip the shutter. Sensors on the device ensure proper push and release pressures and the RCX programmable Brick runs the camera through about 5 hours of automated night time exposures of the night sky, on a tracking mount from the film Auroracam, and initiates its tracking and rewinds automatically as well.
This is the digital age, and I will develop automatic and autonomous devices to take over the tasks that film based imaging required.
Here is a side view of the robotic device, the RCX micro computer is on the right connected to sense switches for button pressure on rewind and to initiate the exposure. The switch on the bottom of the RCX starts the hours long sequence, which fortunately counts down on the cameras top LCD display in seconds. Typical exposures are 5 minutes. The cable on the left is for activating the robotic barn door mounting.
Here's how it works. When the motor rotates the big gear to its stops in the lower position, an arm with a sliding assembly lowers a lever to stop the exposure. When in the lower position, a switch is closed to set the zero point.
The motor is driven CCW for .7 seconds to wind the gear CW and raise the arm to lift the lever and start the exposure by pushing the button. More detail below.
Top view. On the left you can see the Canon electronic cable release box, with a single button. For Bulb exposures, you only need to push it once, it is NOT a two step push in this case.
The lever is the central horizontal bar. When the right side is lifted about 2 inches, the left side which has the axle very near it only pushes down about 3/16 of an inch. This is enough to activate the shutter. Note one VERY important design feature is that even if the motor does not stop turning the gear, the lever will lift no higher and the button wont be crushed. Some designs with worm drives to push buttons will destroy the button assembly if the processor runs away!
Here is an example of a single frame taken with the 10D on a nights run. 30 frames were taken of consecutive fields. CLICK TO ENLARGE