Scanner project question
Cogburn
Posts: 62
I have built some small projects with the BS2 but need a little jump start on this one so I would like to bounce this idea off of some of you gurus and put your suggestions to use. Please feel free to jump in with ANY comments or suggestions.
I would like to build a scanner to scan and score bubble sheets that would have 20 to 25 lines of 4 choices per line. I am thinking of a strip of paper that is 4 inches wide and 11.5 inches long. This could be gravity fed into a slot in a slanted base that would be set at such an angle that would "factor out" the acceleration of the paper through friction. I am thinking that photodiodes or photoresistors would be able to see through the paper when leds are lit on the opposite side of the sheet. I am thinking that the bubbled in choice would prevent the light from registering or at least lower the intensity of light that went through the sheet. This, I would hope would be able to be read as a choice and this would be compared to the correct answer and marked as correct or incorrect.
The correct answers would be put through the scanner one time before any scanning of student answers. These values would be held in memory and used for comparison to the student choices. I also would like the student scores placed on a computer screen with the debug command.
I am needing some direction to get started. photodiodes or photoresistors? Is the BS2 capable of this or would something more be required.
I will create my own sheets with a copy machine so the distance in between and among the bubbles can be played with.
I have priced machines that do this task and they want upwards of 1200 dollars. I think one could be built for less than $100. Anyone have any ideas or suggestions as to how to get started?
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Showing up to school doesn't·mean you are a student any more than crawling up in an oven means that·you are a biscuit.
Post Edited (Cogburn) : 5/20/2008 5:38:25 PM GMT
I would like to build a scanner to scan and score bubble sheets that would have 20 to 25 lines of 4 choices per line. I am thinking of a strip of paper that is 4 inches wide and 11.5 inches long. This could be gravity fed into a slot in a slanted base that would be set at such an angle that would "factor out" the acceleration of the paper through friction. I am thinking that photodiodes or photoresistors would be able to see through the paper when leds are lit on the opposite side of the sheet. I am thinking that the bubbled in choice would prevent the light from registering or at least lower the intensity of light that went through the sheet. This, I would hope would be able to be read as a choice and this would be compared to the correct answer and marked as correct or incorrect.
The correct answers would be put through the scanner one time before any scanning of student answers. These values would be held in memory and used for comparison to the student choices. I also would like the student scores placed on a computer screen with the debug command.
I am needing some direction to get started. photodiodes or photoresistors? Is the BS2 capable of this or would something more be required.
I will create my own sheets with a copy machine so the distance in between and among the bubbles can be played with.
I have priced machines that do this task and they want upwards of 1200 dollars. I think one could be built for less than $100. Anyone have any ideas or suggestions as to how to get started?
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Showing up to school doesn't·mean you are a student any more than crawling up in an oven means that·you are a biscuit.
Post Edited (Cogburn) : 5/20/2008 5:38:25 PM GMT
Comments
1. Have a fifth row of filled in bubbles to use as an index. The system only reads when this row is under your sensors. This would help eliminate false readings due to the paper not moving uniformly through the system.
2. I would put some type of power feed on the unit.
3. To capture the scores, you might look at the PLX-DAQ software that can be downloaded from the Parallax site. This allows you to feed data into an Excel spreadsheet using the DEBUG command.
This type of data collection has been used for a number of years and several companies have been in the market place.
Despite the obvious learning experience, you can probably get a used card reader on ebay to work with. Even getting an old card reader transport mechanism would move you well along the development path. Building a device like this for $100 will be quite a stretch, unless you're not counting the value of the hours of learning time.
Cheers,
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Tom Sisk
http://www.siskconsult.com
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Showing up to school doesn't·mean you are a student any more than crawling up in an oven means that·you are a biscuit.
http://cgi.ebay.com/NCS-OPSCAN-4U-OPTICAL-SCORE-SCANNER_W0QQitemZ360046379403QQihZ023QQcategoryZ3751QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
as a starting point.
Even if it is non-functional, you should be able to use it as a starting platform.
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Showing up to school doesn't·mean you are a student any more than crawling up in an oven means that·you are a biscuit.