P08456: Underwater Light


The Prototype

There will be two prototypes for the Underwater LED Light unit. The first will be a metal housing to be used in pressure testing at Hydroacoustics Inc. The Pressure tests will verify that the mechanical components are capable of withstanding the 216.5 psi of water pressure thatthey will be subject to at 500 ft.

The second prototype was meant to be a breadboard of the elctrrical components that will have a dual purpose. Its intentions were to first, as a proof of concept and a base for debug if problems arise; and secondly, to be used in the testing of the LED's ability to penetrate different cases of water. Unfortunately the beadboard version of the electrical components was unable to be made due to the minute size of the surface mount components. Many of the SMC parts were also only available in that format (no DIP version available). Because of this, in initial PCB order was placed to verify the electrical function

Machining Housing Prototypes

There are three housing portions that need to be prototyped: the shared bullet housing, the light specific LED housing, and the thruster specific motor housing. All prototypes were turned manually in the machine shop. All tolerances were held with the exception of the following:
1) Contour on exterior of bullet housing
2) Contoured counter sinks on edge of LED housing
3) Bolt tabs on nozzle end of motor housing that are used to mount the ducting brace

These features were not functionally critial, and were too complex to include on the first prototype. The exterior contour on the bullet housing was approximated by hand. The features were still included in the final design.

Electrical Prototype

The electrical prototype was originally intended to be a breadboard using DIP mount parts and commonly available resistors and capacitors (like those found in EE Labs). However, many of the parts intended for use were only available in surface mount configuration. These parts were much too small to include in a conventional breadboard, but in order to retain accuracy to the electrical schematics, the parts could not be substituted. It was decided to order a initial batch of PCBs, and populate them with the final parts. The following problems were found once proto-PCBs were completed and tested.
1) Green LEDs were in reversed polarity to white LEDs- needed to be reversed
2) rx and tx pins on microcontroller were switched- needed to be reversed
3) Various solder pad sizes were incorrect from part provieder- needed to be resized to correct measurements
4) Ground pin on microcontroller board needed to be jumped to correct pin on connector
5) Programming connector on microcontroller board reversed- needed to be mounted from other side
6) Short in LED Driver board between 24 V and Ground preventing all operation-short found on edge of board and eliminated by sanding edge and in layouts
7) 5 mil offset found in interboard connector-fixed for final version
 Top view of prototype LED board

Top view of prototype LED board

Top view of prototype USB board

Top view of prototype USB board

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