video turret

Description: This document outlines the complete design for a microprocessor-controlled, environmentally sealed 8-inch video turret equipped with two cameras, offering remote or autofocus and zoom control. It features sun damage protection, 450-degree azimuth rotation, 9-speed scanning, point capability, multidrop network connection, and extensive expandability. The documentation includes detailed photographs, complete schematics, FORTH listings for the multitasking controller based on a low-cost embedded 68HC11 system, sources for hard-to-find parts, a thorough theory of operation, and comments on interfacing. The idea for the video turret originated from a desire to have a video camera mounted on a vessel, leading to the decision to motorize the camera for optimal positioning. The turret is designed to withstand harsh environments, with provisions for thermal protection, overheating monitoring, and an automatic shutter for the color CCD. The design evolved through collaboration at the University of California, San Diego, where it served as a platform for student control engineering projects. After significant development, including the integration of a flexible color camera and various control features, the project reached completion. The turret's two video outputs are connected to a video crosspoint switch, and the control interface has transitioned through various programming languages. The unit is pressurized to approximately 2 psi above ambient to prevent corrosive salt air intrusion, and it includes a local pressure sensor monitored by the internal control system. Additionally, a bright white or silver paint is applied to the interior surfaces of the turret, excluding the camera vision area, to enhance its functionality.

The microprocessor-controlled video turret is a sophisticated device designed for various applications, including surveillance and environmental monitoring. The turret's dual-camera system includes a color camera for standard imaging and an ultra-low light black-and-white camera for enhanced visibility in low-light conditions. The cameras can be independently controlled to pan and tilt across a 450-degree azimuth range, allowing for comprehensive area coverage. The implementation of a 9-speed scanning feature enables the turret to adjust its speed based on the operational requirements, facilitating both rapid sweeps and slow, precise movements.

The turret's environmental sealing is critical for its operation in harsh conditions, particularly in marine environments where exposure to saltwater can lead to corrosion. The design incorporates a pressurization system that maintains internal pressure slightly above ambient levels, effectively preventing moisture ingress. This is complemented by a thermal protection system that monitors the temperature of the turret's internal components, ensuring that the cameras and electronics remain operational under varying environmental conditions.

The control system is based on a multitasking architecture utilizing the 68HC11 microcontroller, which allows for efficient management of the turret's various functions, including camera control, zoom, focus, and the operation of additional features like laser pointers. The use of FORTH programming language enhances the system's responsiveness and flexibility, enabling modifications and updates to be implemented easily.

The turret's output is managed through a video crosspoint switch, allowing for seamless switching between the two camera feeds. The graphical user interface, originally developed in HyperTalk and later adapted for NewtonScript, provides an intuitive control mechanism for operators. Future updates are planned to transition the interface to a more modern platform, Squeak, improving usability and functionality.

In summary, this video turret represents a culmination of innovative engineering and design, integrating advanced technology for effective monitoring and surveillance in challenging environments. Its modular design allows for future enhancements and adaptations, ensuring its relevance in evolving applications.This is the complete design for a microprocessor-controlled, environmentally sealed 8" video turret with two cameras, remote or autofocus, zoom control, sun damage protection, 450-degree azimuth rotation, 9-speed scan and point capability, multidrop network connection, and extensive expandability. Included here are detailed photos, compl ete schematics, FORTH listings for the multitasking controller based on a low-cost embedded 68HC11 system, sources for hard-to-find parts, a detailed theory of operation, and comments on interfacing. The video turret began as so many projects do - yet another one of those irrepressible wild ideas that takes on a life of its own.

Somewhere in the early days of this project, it occurred to me that it might be nice to have a video camera on board. I hadn`t had much luck using a hand-held camcorder in a sealed enclosure underway (too much hassle when things get interesting), so maybe we should mount one on deck somewhere.

But which way should it point Hmmm. OK, so we`ll motorize it. Of course, it has to be sealed to handle the harsh environment. and hey, this would be great for the security system if it could see in low light. OK, so we`ll use two cameras, one color, one ultra low light B&W. Either should be able to point at any angle under software control, and scan between any pair of angles as well. at variable speed, of course. And, since the sun tends to damage things, it should be thermally protected, monitored for overheating, and provided with some sort of automatic shutter to protect the color CCD.

Hey, while we`re at it, why not add a little laser, just for kicks Once begun, ideas like that tend to become design specifications, and that`s pretty much what happened. At the time, we were working in a lab at the University of California, San Diego - and the turret became an ideal substrate for student control engineering projects.

We quickly found out that there were some non-trivial aspects to the design, and although our mechanical engineering guru (Robert Lipsett) did a spectacular job building the physical turret, it was hard to find a student team that could get a controller working reliably. At last, nearly a year after the machining projects were completed, Nathan Parker and Alex Burmester sunk their teeth into a multitasking PWM control system design and did it beautifully.

Their software, virtually unchanged, appears as the bulk of the FORTH listing. Shortly thereafter, we moved to a lab in Silicon Valley sponsored by Apple Computer, and in early 1996 decided to change to a flexible (zoomable) color camera and add a few other features. This led to a rather substantial packaging and refinement project, along with the addition of a servo-actuated vane (built by Ken Glaeser, visiting from UW Madison) and some of my circuitry to handle camera power, zoom, and focus controls.

At that point, we decided to button it up and call it done. and create this document before forgetting all the key details (about 45 copies of this were sold over the next couple of years at $25 each, in the form of a fat documentation binder). The turret`s two video outputs appear as channels on the video crosspoint switch, and the control front end is a graphic interface that was initially written in the venerable HyperTalk, later implemented in NewtonScript, and is now scheduled to be redone in Squeak.

The unit is designed to be pressurized to about 2 p. s. i. above ambient to help keep out corrosive salt air, and a minor but important addition that does not appear in this version of the documentation will be a local pressure sensor monitored by the internal control system. Also, not shown in the photos is a critically important paint job - a bright white or silver paint applied inside the cylinder, covering all surfaces except the narrow band required for camera vision.

This will make the turret a lot less interesting to look at, but shoul