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A Prototype Optical Tracking System Investigation and Development - page 83 / 170

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5.5 Production

69

(a)

(b)

Figure 5.10 (a) The lens screws into the CS mount adapter. (b) The filter attaches to the CS mount adapter.

Focusing the lens

To focus the lens it is rotated inside the CS mount while images are captured using the camera module firmware. When out of focus, the LEDs appear much larger than they are. Rotating the mount towards focus reduces the LED image size. The minimum LED image size is when the LED is in focus. The lens for each module must be focused before the module can be used.

5.5

Production

The PCB is a 50 mm × 55 mm board and contains approximately 80 parts. These parts include the processor, image sensor, regulators, decoupling capacitors, and resistors. The top side of the board contains the image sensor, Blackfin chip, 3.3 V regulator, supervi- sory components, and 10 M Hz crystal (Figure 5.11a). The bottom of the board (Figure 5.11b) contains the flash chip, Blackfin core voltage regulator, and the communications and debugging headers. There are also a number of test points for debugging using an oscillo- scope.

The PCB was manufactured by dvanced Circuits (4pcb.com) in the United States of mer- ica. To reduce the cost of manufacturing and part placement the PCB was produced on a panel as an array of 3 by 3 individual boards (Figure 5.12). The outlines of the boards were

routed so that the boards can be snapped apart after component placement.

solder paste

stencil was also produced by the same company. Most components were sourced from the

merican electronic supplier Digikey (www.digikey.com).

The processor and image sensor come in Ball Grid

rray (BG ) packages. These cannot

reliably be placed and soldered by hand.

PCB assembly company ( ssembly Specialists

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