Kiln temperature controller

General description

This circuit is intended to control a pottery oven. It uses the MAX6675 thermocouple-to-digital converter to measure oven temperatures. An oven schedule will consist of a list of (s, d)-tuples, where s stands for time in seconds and d for temperature in degrees Celcius. When started, the AVR should work through the list of tuples and for each tuple move to desired temperature d taking s seconds to get there.

The circuit uses an LCD display, a rotary encoder and two buttons for its user interface. The oven is controlled through a relay. Since the oven will be in a shed and the users would like to monitor the ovens progress from home, the controller will send its status periodically through a (cheap) 433Mhz transmitter. The See the Wireless LCD display project (which is finished).

Project notes

• max6675 thermocouple-to-digital converter datasheet

Project Status

2010-06-23

Switched to AVR (from SX). Hardware platform now ready (max6675, LCD, LCD backlight control, rotary encoder, 2 switches, relay + driver, transmitter, receiver, led and programming header). First test with 'hardcoded' oven program successful. module tests of max6676, rotary encoder, LCD and relay successfully completed. Total hardware cost: around €33,-, including K-type thermocouple probe.

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