Smart fridge is becoming more and more popular in recent years, as it provides people with better user-experience. 
However, as the machine operators, there are some concerns in their mind, about the payment system, about the buying processes, etc...
Let's see the answers to those FAQs.

FAQ:

Q: How the machine know what customer had taken from the fridge?
A: Every tray there is a weight sensor, by calculating weight difference before open door/after closing door. Machine know what product token.

Q: What if customer took more than 1 product?
A: No problem, support multiple items purchase, the amount will be deducted from his card.
 

Q: What if the customer’s card have only $1 balance but he take all products?
A: You can design how much money required in his card to open the fridge. For example, $20. If balance of his card is lower then that, he will not be able to open the fridge. If customer still take more then card balance amount, it will be lost for operation.

Q: What if the customer put the product back but in the wrong tray?
A: If put back in the right tray, no problem. If put in wrong tray, machine will have voice notice “Wrong operation” and on the screen will show error. If customer ignore the notice and close door. The tray with less weight, will still charge the customer for it.