Our project is a stationary linear barcode scanner made from an IR emitter and an IR detector
B. Project Summary
Originally, we were hoping to construct 1-d barcode scanner using a linear CCD sensor (Charge Coupled Device), which in theory would enable us to scan the whole cross-section of a barcode string at once. However, we have since learned that it was very difficult and expansive to even get a hold of a single unit of a linear CCD sensor (most vendors do not sell CCD sensors in small quantity, say, 1 unit). Even after we managed to acquire a linear CCD sensor (off Nathan’s old scanner), we were still unable to integrate it with the microcontroller since the chip is unmarked and therefore lacks documentation. The lack of proper documentation and the complexity of the CCD sensor operation finally made us realize that constructing a home-made CCD barcode scanner is simply beyond us at this point. With the project deadline only weeks away, we decided to make a linear barcode scanner with photo-detectors instead. The operation of a photo-detector is very simple. Depending on the reflectance of the scanned object, photo-detector simply outputs different level of analog voltage (generally higher voltage for larger reflectance). Using the photo-sensitive nature of a photo-detector, we were able to construct a home-made linear barcode scanner at a very cheap price.
II. High Level Design
A. Project Idea Source and Rationale
Our original goal was to come up with a final project that utilizes most, if not all the knowledge we have accumulated from other projects throughout the semester, and of course, it has to be doable with our current level of technical expertise. We were eventually inspired to make a barcode scanner because Nathan’s grandparents own a Quilting template store and it is a long and arduous process for them to mark price on each of their inventory items (not to mention the amount of price remarking if there is to be a price change for a particular product). After some research on the past final projects, it turned out that a barcode scanner had already been done before. However, the previous barcode group bought a commercial wand-type barcode scanner and therefore their project was mostly software-base. We naturally wanted to do something with barcode scanner hardware. Our first idea was a CCD barcode scanner but we eventually settled with a photo-detector linear barcode scanner (see “Summary” for reason). With no pre-made commercial barcode scanner, our linear barcode scanner project is half hardware and half software.
B. Project Background
There are many types of commercial barcode standard. We decided to use Code 3 of 9, or Code 39 for our project because it was one of the first barcode standards we came across; it was easy to understand and it can encode both English alphabets and numerical digits (among other special characters). Each Code 39 character consists of 5 black stripes sandwiching 4 white spaces. Black stripes, as well as white spaces can be both thin and thick. Code 39’s encoding scheme is therefore binary, with thick stripes/spaces representing 1’s and thin stripes/spaces representing 0’s (shades of the stripes/spaces do not matter since black and white simply allows us to differentiate the thickness of stripes/spaces).
Link: http://instruct1.cit.cornell.edu/courses/e...h257/index.html
B. Project Summary
Originally, we were hoping to construct 1-d barcode scanner using a linear CCD sensor (Charge Coupled Device), which in theory would enable us to scan the whole cross-section of a barcode string at once. However, we have since learned that it was very difficult and expansive to even get a hold of a single unit of a linear CCD sensor (most vendors do not sell CCD sensors in small quantity, say, 1 unit). Even after we managed to acquire a linear CCD sensor (off Nathan’s old scanner), we were still unable to integrate it with the microcontroller since the chip is unmarked and therefore lacks documentation. The lack of proper documentation and the complexity of the CCD sensor operation finally made us realize that constructing a home-made CCD barcode scanner is simply beyond us at this point. With the project deadline only weeks away, we decided to make a linear barcode scanner with photo-detectors instead. The operation of a photo-detector is very simple. Depending on the reflectance of the scanned object, photo-detector simply outputs different level of analog voltage (generally higher voltage for larger reflectance). Using the photo-sensitive nature of a photo-detector, we were able to construct a home-made linear barcode scanner at a very cheap price.
II. High Level Design
A. Project Idea Source and Rationale
Our original goal was to come up with a final project that utilizes most, if not all the knowledge we have accumulated from other projects throughout the semester, and of course, it has to be doable with our current level of technical expertise. We were eventually inspired to make a barcode scanner because Nathan’s grandparents own a Quilting template store and it is a long and arduous process for them to mark price on each of their inventory items (not to mention the amount of price remarking if there is to be a price change for a particular product). After some research on the past final projects, it turned out that a barcode scanner had already been done before. However, the previous barcode group bought a commercial wand-type barcode scanner and therefore their project was mostly software-base. We naturally wanted to do something with barcode scanner hardware. Our first idea was a CCD barcode scanner but we eventually settled with a photo-detector linear barcode scanner (see “Summary” for reason). With no pre-made commercial barcode scanner, our linear barcode scanner project is half hardware and half software.
B. Project Background
There are many types of commercial barcode standard. We decided to use Code 3 of 9, or Code 39 for our project because it was one of the first barcode standards we came across; it was easy to understand and it can encode both English alphabets and numerical digits (among other special characters). Each Code 39 character consists of 5 black stripes sandwiching 4 white spaces. Black stripes, as well as white spaces can be both thin and thick. Code 39’s encoding scheme is therefore binary, with thick stripes/spaces representing 1’s and thin stripes/spaces representing 0’s (shades of the stripes/spaces do not matter since black and white simply allows us to differentiate the thickness of stripes/spaces).
Link: http://instruct1.cit.cornell.edu/courses/e...h257/index.html