I would like to develop a system for counting students getting onto and off of a school bus, and for tracking attendance in classrooms, using ultrahigh-frequency (UHF) RFID. How should I proceed?
One option would be to hire a systems integrator to design the solution and recommend the appropriate hardware and software. If you are intent on building it on your own, I would suggest that you start by defining the requirements. Some key questions to consider are:
• Is this something of which parents will approve?
• Does the system need to record each student's presence on the bus automatically, or can the children be asked to present an ID card upon entering and exiting the vehicle?
• If the system needs to automatically record when students enter and exit the bus, where will the RFID transponder for each child be located?
• Does the system need to be in real time, or can the data be uploaded in batch mode after the bus returns to the school from dropping off the children?
• If the system will upload data in real time, do you want the system to update parents when their kids board the bus to go to school, and again when they leave the bus at the end of the day?
• If the system will update parents, will it tell them where their child exited the bus?
• Will the solution be integrated with an existing attendance-tracking system, or will it be standalone?
The first question is very important. Before you begin designing and building the system, I recommend that you inform students' parents about the plan—explain why you are doing it and obtain their input. You would not want to deploy the system and have parents be surprised when their children come home with a tracking device. This has caused issues in the past, particularly within the United States (see Uproar Over School's RFID Student Tracking).
The second question is critical to determining the type of RFID technology that will be needed. If the students will present ID cards to a reader as they exit and leave the bus, then you will likely want to use a passive high-frequency (HF) system, perhaps Near Field Communication (NFC) so students' phones can be employed instead of cards. But if the system needs to detect the children entering or leaving the bus automatically, you will likely need to use a UHF tag due to its longer read range.
You will also need to set up at least two reader antennas near the vehicle's entrance. This will help determine whether a student is getting onto or off of the bus. If the tag is interrogated first by antenna 1 and then by antenna 2 (both can be connected to the same fixed reader), then the student is likely entering the bus, whereas if the tag is read first by antenna 2 and then by antenna 1, the student is likely exiting. This can produce false information—if a student boards the bus, but then backs up to let another child pass, for example—but you can establish some software rules. For instance, you could set it up so that any read occurring between 3:00 and 3:15 P.M. is a student getting onto a bus (assuming that is when your school day ends), and that any read taking place after 3:30 P.M. is a student leaving a bus (assuming that is the time of the first drop-off). Getting the information correct is crucial if you are informing parents, as you would not want to send a text message saying a student just got off the bus if he or she did not do so.
The UHF badge will need to be worn by all students taking a bus. If children have an existing ID badge they wear, the transponder can be inserted into the badge holder. If not, you will need to issue ID badges and require students to wear them. Again, it makes sense to consult with parents first before going down this road.
You will also need to establish rules regarding where the badges are to be worn, as well as about students swapping badges. Such rules will be important to ensure that the system can read all student IDs consistently, and that the wrong student is not identified as being on a bus, when in fact he or she has actually swapped badges with a friend.
If the system needs to operate in real time, you will need to set up a cellular link so that information about which tags have just been read can be updated in near-real time. If you want to let parents know that their children just got onto or off of a bus, then the software will need to be able to send SMS text messages. And if you want to tell parents where their kids exited a bus, you will need to have a GPS system on the vehicle, linked to the cellular connection.
It would make sense to integrate the RFID system with an existing attendance-tracking system, so that there will be a record of each student boarding or leaving the bus that would then be retrievable via the existing software used by school administrators. This would involve creating a database to store information regarding when each student entered or exited the vehicle. The database, which would be updated by middleware that would interpret and format the tag reads, could be integrated with the existing attendance-tracking system.
Another thing to consider is how the RFID reader, the GPS system and the cellular device will be powered. You would need to wire these systems into the bus's electrical system so that they can draw power from the vehicle's battery.
Personally, I think tracking kids as they get onto and off of school buses, and then sending parents alerts, is a good idea since parents are often at work when children come home from school. Unfortunately, there is no off-the-shelf system to do this that can be deployed quickly and easily.
—Mark Roberti, Founder and Editor, RFID Journal
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