Design Constraint TCSP Team 4 Ethan Price Computation

Design Constraint TCSP Team 4 Ethan Price

Computation Requirements Device needs to: Monitor Microphone Pt. P read IR thermometer, >= 2 Hz process camera input (offloaded) read processed color value update display read RPG input control fan and heater coil track roasting status, estimate completion time

Interface Requirements Camera, IR thermometer, and display all interfaced through I²C

Display Only need to display short phrases, slow refresh acceptable Software support is preferable Has to tolerate evelated temperatures, the higher the better Minimal requirements, cost biggest concern

Display Options NHD-C 220 Bi. Z by Newhaven Display 2 x 20 Characters, I 2 C Interface, 3. 3 Vdd FSTN (+), WHITE LED backlight 3 V, Tranflective, 6: 00, Wide Temp, With mounting holes, Ro. HS Hitachi HD 44780 w/ I 2 C controller 2 x 20 Characters, LED backlight Appears to be a very common display, plenty of sources "Knock-off" displays incredibly cheap ($2 vs. $10+)

Microcontroller We want to use the Arduino software stack, which uses a Wiring language deriviative targeting Atmel u. C's, primarily the ATMEGA series

Microcontroller Needs Minimal processing power 3 analog inputs I 2 C 2 PWM Heat-tolerance No need for low power versions, heater will use orders of magnitude more power

Microcontroller Options ATmega 8 A 8 KB self-programming flash program memory, 1024 -byte SRAM, 512 -byte EEPROM, TWI, 6 channel 10 -bit A/D converter and JTAG interface for onchip-debug One of the smallest ATmega's Atmel recommends for home appliance use ATtiny 2313 2 KB ISP flash memory, 128 B ISP EEPROM, 128 B internal SRAM, universal serial interface (USI), full duplex UART, and debug. WIRE for on-chip debugging Much smaller, it would be tough to work with the SRAM constraint

Camera We need a way to monitor the average color of the beans What we really want is a long range color sensor, giving us the average RGB over a field Low-resolution camera is an acceptable substitue Images will need to be captured and processed, requiring a microcontroller with plenty of SRAM

Camera Options Hacro. Cam PCB with VGA camera (640 x 480), 4 Mbit SRAM framebuffer, and controller (AVR XMEGA) chip already mounted, I 2 C interface Allows us to offload all of the image processing from our main microcontroller, where the Hacro. Cam creates an average color value over the field and returns a value instead of image data Make our own "Hacro. Cam" Still investigating, a few serial-enabled low-res cameras are available, could be combined with another microcontroller and SRAM to make a functional equivalent. Importing this processing into our main u. C would be difficult, considering total processing time would be in the. 5 -2 second range.

IR Thermometer Needs: good accuracy wide temperature range narrow field of view resistant as possible to high heat

IR Thermometer Options MLX 90614 KSF-ACF "-70 to 380°C for object temperature Better than 0. 5°C accuracy in the range 0 -50°C 0. 02°C readout resolution possible" K - larger temp range SF - package B - 5 V C - Temp gradient compensated F - 10 degree FOV

IR Thermometer Options MLX 90616 ESF-HCA Measurement range -70°C to 1030°C Measurement resolution of 0. 02°C Built in thermal gradient compensation sensor fast, stable readings SMBus compatible digital interface