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I have a project requirement to use open protocol RFID tags to control doors handling of a light rail train (also called a tram in Europe). The application must sync and control 2 different doors: one at the train (normal train door opened by driver´s control) and other at the station, also called the platform door. Something as seen in this link here

The idea is, once the train stops at the correct position, when the train drivers commands the train doors to open, the platform door opens in sync. Once tha train driver commands the door to close, the platform door closes also in sync.

To do it, I´m looking for a Gen2 RFID Tag that is externally controlled by a switch or a power connection.

The idea behind the application is: An RFID once in front of its pair antenna sends its data (code). To sync doors, it need to "TURN ON" and "TURN OFF" the RFID reading by an external command to the tag. As the control is in the train, where the tag is located, then I need to control the TAG code transmission.

If I use a normal RFID in this application once the train approaches is position the RFID code is sent, the antenna captures it and command the platform doors to be open.

What I need is to sync the moment when the RFID code is sent with the train door command, so that when the train stops no code is sent (the tag is "off") and when the door is commanded to open it "turns on" the RFID that sends its code that will be interpreted and command the platform door to get opened.

RFID usage is a requirement, not an option.

Advices welcomed.

marked as duplicate by Bence Kaulics, PeterJ, Daniel Grillo, uint128_t, placeholder Jun 3 '16 at 15:21

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  • Trains? Doors? RFID tags? Do you mean you need a microswitch on your model train? – Asmyldof May 31 '16 at 18:12
  • The lightrail train (also called TRAM in europe) has its controlled door... The station where it stops has also a controlled door, also called a platform door.... See example at this link. It´s a real application not a playground... – Mendes May 31 '16 at 18:16
  • Why use RFID for this? The Gen2 spec is highly based around inventory, and I don't think this is what you want. Also, the read distance on a passively powered tag is 3m in the lab, in ideal conditions. You get about 200cm in the field due to the nature of the readers. – b degnan May 31 '16 at 18:30
  • RFID usage is a project prerequisite - I did not wrote the project spec. Gen2 is an option and other open standard can be accepted once it can be externally controlled. About the distance, the tags will be installed in a train position that is no more than 30cm away from the antenna. This is not an issue... – Mendes May 31 '16 at 18:59
  • It is rather unclear. You go straight to the details without giving us an idea of the big picture, and the whole thing gives me a strong feeling of XY problem... – dim May 31 '16 at 19:03

While I will echo all of the posts that RFID is not the proper technology for this, unless you are using the ID to certify the door to location. And with that, the positioning is not as accurate as other switch or optical sensor options.

We are using Impinj Monza-X RFID chips with a PCB antenna in an application. This allows read and write via RFID or with I2C as an EEPROM. Depending on model, you have 2048 bit and 8096 bit chips (with some of that reserved), which is more than enough to store some data. However, it sounds like you need to swap this data often. This may cause an issue with write cycles on the chip, making the memory locations error. I have not located total write cycle counts on the chips, it is more of write counts versus retension time. This is more realistic, as no one really uses RFID as a real-time changing data exchange format in high frequency.

Where you may be able to get this to work is with the I2C control of the Gen2 Ack response. I have not worked with this at all. However, my understanding is that I2C data is added to the response without using NVM, thus not using up your write cycles of memory and allow an instant change of data (sending your off and on signal in that case).

We are using this device for a much slower changing data. We will periodically flush usage data to this MonzaX and this allow retrieval of that data via RFID, if the device is off or fully discharged. It is also useful for changing state of a device (i.e. virtually bricking it) until it is properly provisioned via custom software with EEPROM or RFID based memory writes.

  • What communication technology would you use? Something inductive still makes sense even if you don't use vanilla RFID, right? – Tali Aug 29 at 12:11

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