Mbed Coffee Roaster

Overview

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.

Components used

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.

Nichrome Wire
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.

Control System

/media/uploads/ericspatterson/controlsystem.jpg

Heating System

/media/uploads/ericspatterson/heatingsystem1.jpg /media/uploads/ericspatterson/heatingsystem2.jpg

Pin Connections

Keypadmbed
GndGnd
Sdap28
Sclp27
Irqp26
VccVout
uLCDmbed
5vVout
GndGnd
Txp10
Rxp9
Resp11
Temp Sensormbed
VinVout
GndGnd
D0p6
Csp20
Clkp7
SSR1mbedAC Wall Outlet
p1-Gnd (motor)
p2-Power (motor)
p3p22-
p4Gnd-
SSR2mbedAC Wall Outlet
p1-Gnd (nichrome wire)
p2-Power (nichrome wire)
p3p30-
p4Gnd-

Video

Coffee Beans Before and After

/media/uploads/ericspatterson/coffeebeans.jpg

Code

Import programFinal_Coffee_Roaster

Final project code

PowerPoint Presentation

/media/uploads/ericspatterson/mbed_coffee_roaster_final_presentation.pptx


Please log in to post comments.