What would I need to build an RFID system that could record attendance numbers, and how should I go about doing so?
I'm not sure if you are taking attendance at a school or at an event with different sessions, but there are several ways you could go about it—some efficient, and some less so. The cost might vary significantly, depending on which option you choose.
A simple method would be to have students wear name badges on their chest (assuming you are tracking children at a school), each containing a photo and an embedded passive ultrahigh-frequency (UHF) tag. You could have teachers walk around with a handheld interrogator, which they would point at each student in order to capture attendance data. The ID number in each tag read could then be transferred to a host system by cradling the handheld, or via a Bluetooth connection to a PC. This would probably be the least expensive way to go, but it would only be marginally better than reading each student's name and having him or her answer "here."
A more automated system would be to utilize the same UHF badges, and to situate a reader antenna above the door, so that it could capture the ID of each student entering the room. Given that the human body is mostly composed of water, and thus absorbs RF energy, this system might require more than a single antenna, which would increase the cost. And if the rooms are spread out, you might require a reader in every room.
There are phased-array antenna systems, such as Mojix's STAR system, that could perhaps capture students entering rooms down a hallway (see The Brightest Star and Mojix Takes Passive UHF RFID to a New Level), but having many hallways would probably require having a large number of receivers. An active RFID real-time location system (RTLS) could be used to provide real-time data regarding students' locations, but the tags would cost $30 apiece or more, so if you have a lot of students, that could get expensive.
The best way to proceed might be to find a knowledgeable systems integrator who could consider your layout, the number of students and other factors, and then recommend the most cost-effective system to meet your needs.
—Mark Roberti, Editor, RFID Journal
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