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it would be interesting to create a wipe mechanism to erase the existing QR code (may be a belt/sander, or a laser like those rust cleaning lasers), and print a
by chii 2y ago
it would be interesting to create a wipe mechanism to erase the existing QR code (may be a belt/sander, or a laser like those rust cleaning lasers), and print a new one on (may be even use the same laser as the wipe!).
- grishka 2y agoIf you really want a system that uses optical scanning and allows one ticket to be used multiple times, just make sure that there's enough room on the ticket for one QR code per trip. When validating, you'd print a new code in free space. You can also either print something over the old one to invalidate it, or just leave it and let the system itself figure out which of the codes is newest.
- chii 2y agoi'd assume the QR code would contain a record of the transactions, but yea, i hadn't thought about multiple trips that overlap.
- tjohns 2y agoIC transit cards in Japan use heat-rewritable ink for something similar. The ticket vending machines print your monthly transit passes right onto the face of your card at the beginning of the month, and erase it after it expires. It's not a QR code though. Just human readable text for bus drivers. (Turnstiles in the subway still read the pass via NFC.)