Yoctopuce has a self-service coffee machine. To get a coffee, all you have to do is walk over to the machine, place your cup underneath, press a button and wait. This wait can sometimes be a little long, because the machine has to grind a dose of coffee beans and possibly heat up if it hasn't been used for a few hours. It therefore happens quite often that the "customer" goes off to do something else while waiting, and forgets to come back for his coffee, which will be found cold by the next "customer". To put an end to this rather dumb waste, we've found a solution thanks to the brand new Yocto-RFID-15693.
Who let their coffee die?
RFID power!
The idea is to place a self-adhesive RFID tag under everyone's cup and thus detect if a cup is left under the coffee machine for too long. As it happens, we've noticed that the Yocto-RFID-15693 has no trouble detecting the cup if you place the RFID-Ant-13.56 antenna under the table where the coffee machine is placed. In fact, the cup is detected if it's within an area of around 10x10cm from the antenna, which is just perfect for our application.
The start of a solution: a cup with an RFID tag
In practice, this project is relatively trivial: we simply mounted on a support made of cut acrylic glass:
- A YoctoHub-Wireless-n for network communication
- A Yocto-RFID-15693 reader
- An RFID-Ant-13.56 antenna
Rather than having a standard WiFi antenna protruding, we used a self-adhesive UFL-Wlan-Flex-Antenna antenna. The whole thing is screwed to the underside of the table on which the coffee machine sits.
An RFID reader + a WiFi hub and you're done!
The system is powered by a simple USB charger and driven by a Python script running on a remote machine. The basic operation of the script is quite simple: as soon as an RFID tag is detected, a 120-second countdown begins. If the tag is still there when the countdown ends, the Yocto-RFID-15693 buzzer is triggered.
Improvement 1
The Yocto-RFID-15693 features a user-controllable RGB LED, but as in our case this LED is located under the table, we took advantage of the possibility of adding additional LEDs to integrate an LED strip directly into the thickness of the table. The strip lights up green when a cup is detected and flashes red when the cup has been forgotten. As well as being spectacular, this provides a simple way of ensuring that the system is centered and can see the cups. Indeed, as the coffee machine is simply placed on the table, it's not impossible for someone to inadvertently move it a few centimetres.
An LED strip integrated directly into the tabletop
Improvement 2
As some of us are used to working with headphones on, it's not certain that we can hear the buzzer on the Yocto-RFID-15693, so we decided to use our DMX512 projector, still installed on the ceiling since our experiments with the DMX512 protocol. When the countdown nears the end, our script powers up the projector using a Yocto-PowerRelay-V3 and, at the end of the countdown, the projector is aimed at the workstation of the guilty slightly distracted member of staff.
If your workplace is bathed in red light, you've forgotten something
A little subtlety: the orientation of the spotlight corresponding to the workstation of the owner of each cup is not pre-programmed in the control script, but stored in the memory of the tag attached to each cup. So there's no need to modify the code to add a cup to the inventory.
The control box for our DMX512 spotlight
All the electronics needed to control the projector, namely a YoctoHub-Ethernet, a Yocto-PowerRelay-V3 and a Yocto-RS485, are installed in an independent enclosure, making the projector control available to other similar projects.
Conclusion
With a few Yoctopuce modules, we've easily solved a rather annoying problem in a rather amusing way. Obviously, it only works because the part of the coffee machine on which the cup is placed is made of plastic. On the other hand, we don't know how long the RFID tags will resist washing, so we're thinking of varnishing them to make them more water-resistant, but we'll have to wait and see.
If you want to have a look at the script that drives the system, you can get it from here.
