Thinking about making a vending machine for my schools IEEE room. I thought about coin-op but us millenials hardly carry cash. I'd love to operate it on a pay platform everybody has easy access to.
If you use Facebook Messenger you have Facebook Pay. It's free. You enter a debit/credit and it uses that to send/receive money, Facebook isn't even a money-holding-middle-man like PayPal. So the $0.50-$2.00 candy/drink items would be dispensed via FB Pay amounts, perhaps $0.54 could be slot A, $0.55 could be slot B and so on.
Has anybody dealt with or thought about this also? I'd love to hear your ideas/code/input/results/failures before I proceed!
Any such system will require public-key encryption which is beyond the capability of the simpler Arduino boards (AVR based boards). (If public-key encryption is not required you need to stay away from it.)
A simple accounting system worked well at our local makerspace. The system tracked account balance based on member ID. From time-to-time an administrator would send bills. That kind of system is low risk, can be done with nearly any processor, and is easy to get working. The drawback is the necessity for someone to be a bill collector.
I once designed a system with SMS payments. There are companies offering SMS-based payment solutions.
In my system, the user sent an SMS with a code to a SMS gateway, the gateway forwarded the SMS to the vending machine, and the machine dispensed the ordered product.
In the Arduino Code, I only had to check if the message recieved was from the SMS gateway.
This is a risk free solution, but of course, it's not free.
Vianett is one of many companies to offer this kind of solutions.