Final Design

Camera Design

            Compared to many off-the-shelf digital cameras, the GoPro cameras proved to be one of the most inexpensive and highest quality cameras in the market. Used by many action sport enthusiasts and scuba divers, the robust GoPro cameras can be easily modified to satisfy underwater imaging needs. A waterproof housing came with GoPro camera, which was beneficial for mounting purposes. Another useful feature of the GoPro camera is the back port, which allows the camera to be connected to the microcontroller.

Processor and Sensor Design ChoicesTemperature/Humidity sensor

           A humidity sensor in addition to the temperature sensor is configured in the design. The humidity sensor monitors possible leaks or condensation that might form inside the vessel which can harm electronics or even affect imaging quality. A sensor which included both temperature and humidity sensing was therefore included in the sensor system. It was concluded that this was a favorable design solution because it would reduce size of overall system and would simplify retrieving data because the processor would retrieve data from a single device instead of two.

Compass with tilt compensation

            The compass is required to give information regarding device orientation. A compass is designed to detect location of magnetic north and hence can provide information regarding device at any given instant. One issue that conventional digital compasses usually come across is the fact that when tilt occurs in the device for which we wish to determine the orientation, the compass will not give the accurate location of magnetic north. Since the Snow-Cam imaging system will be underwater, it is likely that the device will undergo some kind of tilt. In order to make up for inaccuracies in readings due to tilt, a compass with tilt compensation was employed as a desirable design choice. The HMC series Honeywell compass with tilt compensation and I2C communication enabled was therefore selected for the system.

Pressure sensor

            The pressure sensor is used in the system to monitor both pressure and depth. A pressure sensor able to monitor high pressures as is required for the depths that the imaging system will reach was chosen. In addition the NPT connection for the pressure sensor was chosen at 1/8 of an inch. In regards to the design choice for depth sensing it was decided to calculate depth from pressure using the relation Equation (1) because this meant using one sensor for two functions thus reducing money spent. An initial design consideration dealt with using a separate sensor for depth sensing, sonic sensors are able to measure distances using sonic waves. However, being that such a sensor would have to sense the surface floor and then calculate depth from that this process seemed to be highly inaccurate therefore it was decided to calculate depth from pressure.

Microprocessor

Camera optics: · Lens type: Fixed Focus · Aperture: f/2.8 · Focal length: 5mm · Field of View: diagonal angle of view of 170°, a horizontal of 165°, and vertical of 160° Imaging: · Resolution: 5 megapixel · Sensor Type: 1/6.35cm (1/2.5 in) HD CMOS with 2.2µm-sized pixels · Exposure: Fully-automatic, with an ultra-low-light sensitivity of >1.4 V/lux-sec · Capabilities to record vides with 1080p at 60 fps Storage: · Memory: Class 4 or higher SDHC up to 32 GB capacity Power and battery: · Charging capabilities via USB 2.0 · Battery life: Approximately 2.5 hours Lenses:

The lenses originally on the GoPro HD Hero caused an unwanted fisheye distortion that was especially visible underwater. In order to fix this effect, the lens must be modified so that was is flat or replace the whole lens setup for a new one. A new lens was bought to replace the stock lenses. The lens used for the camera design was the DSL 300 lens from Sunex Digital Imaging Optics. The lens has a 19° horizontal field of view and 14° vertical field of view, a 17.3mm focal length and an aperature of f/4

GoPro HD Hero was used with a class 6 16GB MaxFlash SDHC memory card to store the images of the marine snow. Due to space constraints and backport accessibility issues, the waterproof housing was not used in the final design of the camera. The camera was programmed to take a picture every 5seconds. In order to connect the GoPro cameras to the microcontroller, two wires were soldered onto two connection points to electronically trigger the push button as shown in Figure 11.

Exterior Hull Components

The exterior and hull assembly was comprised of four separate parts: the nose cone, the end caps, the cylinder housing and the framing structure.  For each of these components all functional requirements had to be considered; such as structural integrity under pressure, hydrodynamic shape and optical characteristics.

Nose Cone:

            The nose cones will be located at the bottom of the vessel and provide a smooth curved surface for the water to contour around. The curvature of the nose cone was designed to minimize the impedance of the vessel through the water. The ellipsoidal shape would have a 3: 1 major to minor axis ratio.For assembly, a threaded rod was used to connect the nose cone to the bottom end caps.

End Caps:

The end caps of the vessel were an important component which served many functional needs of the device. They provided the waterproof seal, structural integrity as well as a means to mount all additional components. The waterproof seal was a double o-ring bore seal. When considering the thermal expansion and contraction of the vessel as the ocean temperature decreases, it would have been ideal to construct the entire prototype from the same material. Acetal copolymer would also be non-corrosive and provide adequate strength but it also has a coefficient of expansion that is comparable to that of the acrylic. The coefficients of acrylic and acetal are 81x10-6 m/m*K and 106.5x10-6 m/m*K respectively.

Housing Cylinder:

Different materials were researched and cast acrylic was determined to be the most appropriate material to be used. It has superior optical transmission of approximately 90%, mechanical compressive yield strength of 124MPa (18kpsi), is light-weight and relatively cost effective. Two cast acrylic cylinders with 0.127m (5 in) diameter by 0.914m (3 ft) were purchased for $515.16.

Connecting Framing:

            The connecting frame will attach the two cylinders together and provide for the mounting positions that the entire Snow-Cam will be lowered and raised on. The connecting frame consists of one inch thick Polyoximethyline clamps that tighten onto each cylinder and then attach to one another with a strut bar. Figures 9 and 10 show a detailed CAD of the sub-assembly.

            The underwater imaging system designed for the snow-cam project will require the use of a number of electronic components which will be synchronized and controlled. In order to satisfy such control needs a microcontroller will is included in the camera vessel. As far as requirements for the processor, it is desirable to choose a microprocessor that is compact yet efficient enough to comply with the control needs of all the sensors. In addition, the microprocessor should have enough I/O and analog pins to connect all of the electronic components needed. In addition, it should enable easy installation of a USB port or have a USB port integrated. Furthermore, the microprocessor should be inexpensive and not require installation of expensive software for programming and compiling. Initially the affordable Teensy ++ , at $27, was considered for the system, this microprocessor is Arduino compatible and is quite compact, however it was decided that the Arduino Uno would be a better design choice due to the wide variety of Arduino library readily available for electronics included in the system here Internal Framing            The internal frame is a vertebrae-like structure, which holds attached devices. The frame is housed along the entire length of the device, supporting the entire internal weight and offering slight protection for sensitive components. The interior frame is fixed to the end cap. The top end cap is the access port to the Snow-Cam, after opening the top end cap, the interior frame slides out in one piece. To prevent shock and unwanted movement, the bottom end cap has a vibration dampener attached to it. While the Snow-Cam is in use, the interior frame presses against the dampener.             In order to avoid deformation, the internal frame should remain out of contact with the external structure, which will deform slightly in deep water. To avoid the exterior cylinder from contacting interior frame, the internal frame diameter is to be a quarter inch less than the inner diameter of the cylinder.             Internal structure consists of an array of platforms. Each level consists of a platform and each platform is attached to the spinal structure. Three long rods make up the vertebrae. Circular platforms are fixed to the rods by using tubular spacers that slide over the rods but not the platforms. A compressive spring and nut at the top end of the rods push the spacers into the platforms, preventing any shifting or vibrating movements.             The interior frame holds five cameras. The cameras are fixed to each platform. The number of platforms equal to the number of cameras plus enough chambers to house batteries, sensors, lights and processors. 

 

Power Management

Performing a power consumption calculation allowed the team to decide the type of battery and number of batteries the system was going to need to perform the mission. For safety reasons, the use of a smart battery was the first requirement. . Lithium-ion batteries may have an unpredictable behavior under high pressures for long periods of time1. Therefore, the battery needed to have an integrated microcontroller that could shut off the power system in case of unusual behaviors. The microcontroller inside the smart battery also prevents the system from draining the battery and shuts off before this happens. The batteries chosen had capacity of 95Whr and 6.6Ah.

A circuit diagram was utilized to represent the camera, flex block, LED and power regulator. Efficiencies of components were taken into consideration when calculating this value. A safety factor of 20% was incorporated to the results. Another consideration taken was that each LED duty cycle. It was determined that each LED was going to be on only 33% percent of the mission time.

SNOW CAM UPDATES

EXCITING UPDATES TO THE SNOW-CAM COMING SOON!

V1and V2 represents the smart batteries which are 2 batteries of 14.4V connected in parallel. Device A represents the voltage regulator which has an efficiency of 90%. The voltage regulator outputs a voltage of 12V for lights and 5V for cameras. The 5V regulated voltage is directly connected to the five cameras which draw a current of 0.5Amps. The 12 volts are then connected to a current regulator and a voltage booster which is represented by device B and device C. The current regulator and the necessity to use two voltage boosters known as the flexblocks. The details will be discussed in the LED driver section. Device B outputs a voltage of 42V, whereas device C outputs a voltage of 28V and constant current of 0.7Amps, a necessity for the LEDs to function properly. Notice that the flexblocks have an efficiency of 90% as well. The diagram above is an accurate representation of the way the system is connected. Please refer below for power consumption calculations.