Makerspace staff exert much of their time watching over students and verifying safety training… a process that is mundane, imperfect, and begs for automation. Our motivation was to non-obtrusively enforce the safe and sustainable use of machinery in the Makerspaces across campus through RF student ID verification against a user database - if a student is not trained, power is cut to the tool and it will not turn on. If a student is trained, the tool is enabled.
The system is diagrammed below. A Raspberry Pi acts as a Wi-Fi access point and MQTT broker for Arduino microcontrollers in the Makerspace, and it communicates with the external database to authenticate users trying to enable tools. The complete workflow is as follows (please watch the Video above for the simpler workflow. It is much easier to "show" this project than to "tell" about it).
- A user inserts their ID into the 3D printed "Card Holder". The Holder holds the card such that the RFID element hovers over an RFID reader. A Wi-Fi Arduino inside the Holder detects that a card has been placed and reads the UUID from the student ID.
- The Wi-Fi Arduino publishes a MQTT message to the Raspberry Pi in the room asking for user authentication, and notifies it which tool the user is trying to use. The Arduino changes a status LED to yellow to signify that authentication is underway.
- The Pi asks the main Makerspace server if the user is authenticated for the given tool and the server responds.
- An optional buddy system is also supported in that a tool can require a room administrator to put their card in a separate "buddy" Card Holder.
- If authenticated (and a buddy is present if required), the Pi publishes a MQTT message to a separate Wi-Fi Arduino that controls power to the tool via a 120V relay. The Card Holder Arduino also receives this message and changes the status LED to green to signify that the user is authenticated.
- The Arduino enables the tool through the relay and the user can do their work. The system can detect if the tool is prematurely switched on as it turns on the relay (e.g. if the previous person forgot to turn off the tool and simply grabbed their ID and left), and quickly switches the relay off as a failsafe. A buzzer makes noise to let the user know to switch off the tool for the relay to be enabled.
- If a user leaves their ID on a Card Reader but does not power on the machine for a certain time threshold, an email is sent to them stating that they either forgot their ID on the Card Reader or are being unsafe by leaving tools enabled and unused for long periods of time.
- When the user is finished, they take their ID off the Card Reader, which turns the status light to red and triggers a MQTT message from the Card Reader to the Pi, which then publishes a MQTT message to the relay-controlling Arduino to turn off the relay. If the user takes their ID off the reader without switching off the tool (as detected through current monitoring), a buzzer makes noise and power to the relay is cut.
| Component | Quantity | Total Cost |
|---|---|---|
| Wi-Fi Arduino MCU (ESP8266) | 2 | $20 |
| RFID Reader (MFRC522) | 1 | $5 |
| RGB LED (Adafruit Neopixel) | 1 | $1 |
| Relay (PowerSwitch Tail II) | 1 | $26 |
| Current Sensor (30A Split Core from Sparkfun) | 1 | $10 |
| Piezo Alarm (Optional) | 1 | $3 |
| Power supply for MCUs | 2 | $10 |
| Assorted jumpers | ||
| PCB board | ||
| 3D printer filament | ||
| Some sort of metal lock box? | ||
| $75 |
| Component | Quantity | Total Cost |
|---|---|---|
| Raspberry Pi 3 | 1 | $35 |
| 2A Wall Adapter Power Supply (USB Micro-B) | 1 | $8 |
| $43 |
All arduino code has been uploaded
All EAGLE PCB CAD files have been uploaded
All SolidWorks CAD files have been uploaded
In-Room Pi Access Point files have been uploaded - SD card image available by request
The Database has been defined but the external server code has not been uploaded