Remote Touchscreen-Controlled Defense Turret Senior Design Documentation Courtney Mann, Brad Clymer, Szu-yu Huang Group 11

USB Webcams

Thus there were plenty of pixels - even at maximum range - with which to calculate the centroid of the target for the maximum probability of successful impact. That vastly reduced amount of data throughput – compared to a 1600x1200 pixel camera - meant faster processing and therefore quicker response. That made this camera, despite its age and simplicity, attractive for this project. Unfortunately, because the system needed to be able to track moving targets, and a frame-rate of 15 fps made moving objects appear blurry at a very low velocity, it was clear that this camera would not work in the final project.

Since the existing QuickCam was too old, it was logical to look at a newer camera of a similar type. The choice examined was the Logitech QuickCam Orbit AF(Logitech). This camera featured a frame rate of 30 fps, which meant a sufficient frame rate with which to capture the images of moving targets without blurring. The resolution maxed out at 1600x1200, but the camera could be set for lower resolution, allowing the lower data throughput which would be desirable for such an application. Less desirable, however, was the rounded plastic housing present which this device featured; it did not appear sturdy and seemed as though it would be difficult to mount. Still, the relatively low price point of $129.99 could potentially offset the worries about its housing. After exhaustive searching, there were no specifications about power usage available online for any USB cameras; however, in investigating the standards for USB devices, the maximum is 2.5W and thus, this figure was used in the group’s power considerations.

Infrared

Infrared cameras are attractive because they operate in the absence of visible light, but detect the motion of objects based upon their near-IR heat signatures; this is a feature which all of the project’s targets have since it is designed to track humans.

The first IR camera investigated was a Sony CM307. This camera is small and cheap, but it was discovered that it used a BNC video-out rather than USB, and an external converter would add needless complexity. Converters from ambery.com are reasonably priced at $28.00 though, so the option of using such a device was not immediately overturned. However, at a realistic price point IR cameras have long range blurriness issues, so the group discovered that usable cameras are initially cost-prohibitive. An alternative, made from information available on hoagieshouse.com (Hoagieshouse.com), shows that it is possible to modify a visible-spectrum camera to operate in the infrared spectrum. The procedure is to disassemble the camera, find the IR filter, and remove it; then to manufacture an IR-admitting and visible-spectrum blocking filter from a black area of film negatives; and finally, to install this filter, and reassemble the camera. This procedure is both time-consuming and fraught with uncertainty, and thus the group chose to avoid it. The mounting of this camera appeared to be more difficult than the group desired, which also fed into the decision not to use this camera.

The high-cost option, which would be the most desirable if cost is disregarded, presented the group with an Edmund Optics NT56-567(Edmund Optics). This camera outputs 768x494 pixels, which was in the range the group desired, and remarkably, operated in the range of 60-100,000 fps. The mounting for this camera is a pre-threaded socket on one side of the device. Clearly, by the specifications, this device would have met the requirements of the project. However, the camera cost $1,995.00, and was immediately rejected as a possibility in the prototype design, since it would have occupied just under a third of the budget allotted to the group by Workforce Central Florida.

At the reduced cost of $495.00, maxmax.com (maxmax.com) offers a modified version of a Sony DSC-S980 which operates in the IR-only range. However, the battery life when operating in video mode is greatly reduced, and the cost – though lower than the NT56-567 - is still somewhat prohibitive. Additionally, though it is likely a website error, the frame-rate specification is only 1 fps, which clearly did not meet the project’s needs, and thus this camera was rejected as well. Also, this was a handheld consumer-grade camera with no permanent or secure mounting hardware readily available, and thus did not immediately appeal.

Other options explored included the VH HK High Tech Limited brand’s VGSION USB Camera, available at alibaba.com (alibaba.com), which presented a frame rate of 30 fps and VGA resolution, which is the 640x480 previously determined to be desirable for this project. At a price point of $46, this camera presented a very viable option, though there was some concern about the lead time of acquiring the product from the supplier in Shenzhen, China. The base of the camera featured three mounting holes which could easily be mounted onto a wood framework.