Changes

==Receiver System Update: Baby Black Box==

==Receiver System Update: Baby Black Box==

[[File:BBB_night_test.png|frame|right|Baby Black Box uses a Fresnel lens similar to System II]]

[[File:BBB_night_test.png|frame|right|Baby Black Box uses a Fresnel lens similar to System III]]

The latest OpComms receiver system, named ''Baby Black Box'' is an update of the older [[OpComms System III#Fresnel Lens|Fresnel lens receiver]].  The design goals for the update were three: (1) to decrease weight, so as to decrease strain on the motor, (2) complementarily, to decrease torque on the motor, particularly in the axis of altitude rotation, and (3) to more finely focus light into the photodetector system.

The latest OpComms receiver system, named ''Baby Black Box,'' is an update of the older [[OpComms System III#Fresnel Lens|Fresnel lens receiver]].  The design goals for the update were three: (1) to decrease weight, so as to decrease strain on the motor, (2) complementarily, to decrease torque on the motor, particularly in the axis of altitude rotation, and (3) to more finely focus light into the photodetector system.

The first two goals were addressed by purchasing a Fresnel lens with a slightly shorter focal length than the previous system, allowing the whole receiver to have a smaller depth, and by changing the format of the frame from a Duron (hardboard) cube to a pyramid structure composed of carbon fiber, plastic, and foamcore.  The carbon fiber framing provides the structural element for Baby Black Box, ensuring that the thin Fresnel lens is not under any external loads and therefore will not deform.  In addition, an effort was made to provide a mounting point calibrated to the center of mass of Baby Black Box, such that the torques were balanced about the axis of altitude rotation of the motorized mount.  Due to the pyramidal shape, this resulted in a reduction of torque about the horizontal axis as well.

The first two goals were addressed by purchasing a Fresnel lens with a slightly shorter focal length than the previous system, allowing the whole receiver to have a smaller depth, and by changing the format of the frame from a Duron (hardboard) cube to a pyramid structure composed of carbon fiber, plastic, and foamcore.  The carbon fiber framing provides the structural element for Baby Black Box, ensuring that the thin Fresnel lens is not under any external loads and therefore will not deform.  In addition, an effort was made to provide a mounting point calibrated to the center of mass of Baby Black Box, such that the torques were balanced about the axis of altitude rotation of the motorized mount.  Due to the pyramidal shape, this resulted in a reduction of torque about the horizontal axis as well.

The connections for Baby Black Box were 3D printed in ABS plastic.  Corner mounting points set the angle between carbon fiber rods to precisely control the focal distance of the Fresnel lens, and snap connections secure the photodetector in place, as well as the foamcore sides and lens cap, which serve to protect the optics of the device and to screen out external light (noise).

The connections for Baby Black Box were 3D printed in ABS plastic.  Corner mounting points set the angle between carbon fiber rods to precisely control the focal distance of the Fresnel lens, and snap connections secure the photodetector in place, as well as the foamcore sides and lens cap, which serve to protect the optics of the device and to screen out external light ([[Signal-to-noise ratio#Noise|noise]]).

To address the third design goal, a secondary aspherical lens was purchased. An enclosure was created to fix this lens directly to the photodetector, with the intent that the focal calibration of this lens would be much less sensitive to misalignment from transport and handling.

To address the third design goal, a secondary aspherical lens was purchased. An enclosure was created to fix this lens directly to the photodetector, with the intent that the focal calibration of this lens would be much less sensitive to misalignment from transport and handling.

Further details of Baby Black Box can be found in the [[System IV Mechanical Design Log]].

Further details of Baby Black Box can be found in the [[OpComms System IV Mechanical Design Log|System IV Mechanical Design Log]].

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File:BBB_uncovered.jpg | <center> Baby Black Box incorporates an aspherical secondary focusing optic fixed to the photodetector. </center>

File:BBB_uncovered.jpg | <center> Baby Black Box incorporates an aspherical secondary focusing optic fixed to the photodetector. </center>

File:BBB_covered.jpg |<center> Rigid foamcore covers snap onto each side with 3D printed plastic clips </center>

File:BBB_covered.jpg |<center> Rigid foamcore covers snap onto each side with 3D printed plastic clips </center>

File:BBB_test_stars.jpg |<center> A preliminary 10km test with Baby Black Box </center>

File:BBB_test_stars.jpg |<center> A preliminary 10km test with Baby Black Box at [[W6YX]] </center>

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