Arduino and Lots RFID Data

Hello - I have an upcoming project where an rfid tag needs to be read, if it is an authorized tag and if it has not been scanned in that given day, the arduino with trigger a 30 second delay timer and them trigger a 30 second usage timer hooked to a relay. So the program is pretty simple except it needs to keep track of 400-500 rfid tags and whether they have been used already in a given day.

I was thinking about using the internal eeprom which I think can store 256 tags and then add an external eeprom chip for the remaining. The other option might be an sd card. Operating temperatures will be outside in dallas, tx. This can give us 100-105 deg f in the shade. I am guessing another 20 deg with sun on an electrical box.

Questions I have:

  • Will the operating memory be big enough to load all 500 tags at startup?
  • Should I not load the tags at startup but instead just read the eeprom for each tag, each time a tag is scanned? Will this slow the program down?
  • Should I hard code the tags in place? I think 500 will give me 50-100 extra cards and I could issue these as needed when a card is lost or damaged - this could run a couple of years without reloading the program
  • Will an arduino be fast enough? How long will an operator need to wait for 500 comparisons to be made and check daily usage?
  • Should I marry an Arduino with something like a raspberry pi? I have never done this before. Will this speed things up or manage data better? Is that reliable for extended uasge?
  • Is there a better way to skin this cat?

Thank you,

Anthony

Take a look at progmem. Every Arduino I can think of has enough for you to store 500 tags - by the look of your math, you’re storing eight bytes for each.

Hello Wildbill - I think the tags or standard that I am using has 4 bytes per tag, so I took 1kb / 4 to get 256 on the arduino itself and then an external chip for another 256. I don't have a program yet, just trying to avoid writing it several times and possible getting more hardware late in the game which I typically do.

Thank you,

Anthony

In that case, just get yourself any Arduino like device that has more than 2k of RAM and you can just hard code the tag Ids into an array. Often, folks with a similar problem use an SD card to make the system more flexible, but you may decide that it's ok to have the reprogram the device on occasion.