Mbed Coffee Roaster
by Eric Patterson, Elza Mathew, and Erin Deye
For our design project we created a temperature controlled coffee roaster. We used a nichrome wire to roast the coffee beans and an AC motor to rotate the basket holding the beans so that they were roasted evenly. A thermocouple read in the internal temperature, and a hysteresis controller was used to regulate the heating element. The user is able to control the temperature of the system using a touch panel. They are also able to monitor the temperature and elapsed time on an LCD screen.
Here is a list of the components that we used along with the LPC-1768 mbed.
LCD Screen (uLCD-144-G2)
We incorporated an LCD screen so that the user could monitor the current temperature as well as the elapsed time.
Capacitive Touch Panel (MPR121)
The touch panel allows the user to change an set the temperature as well as turn on and off the motor.
K-Type Thermocouple (MAX31855)
A thermocouple was used to read in the internal temperature of the heating system.
Two Solid State Relays (SSR-40DA)
Two solid state relays were used to rcontrol the motor as well as the nichrome wire.
High Torque Low Speed AC Motor
We used a motor in order to rotate the basket of beans so they were roasted evenly.
We decided to use a 19-AWG nichrome wire for our heating element. This choice was ideal as it was cheap and could easily heat up to 500 degrees. A hysteresis controller was also used to regulate the heating element.
Misc. Materials Needed
We needed a basket to hold the coffee beans which was able to withstand high temperatures, as well as a box to hold the entire heating system. We also used ceramic supports for the nichrome wire.
|SSR1||mbed||AC Wall Outlet|
|SSR2||mbed||AC Wall Outlet|
|p1||-||Gnd (nichrome wire)|
|p2||-||Power (nichrome wire)|
Coffee Beans Before and After
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