Ceramic Kiln Retrofit

Hardware

• Replacement coils (custom manufactured to spec): 2500 W, 240 V, channel 102 × 0.5 × 0.5 in, target ~23 Ω, 1300°C application, and surface loading ≤ 15 W/in² for element longevity.
• Sensing & control stack: K-type thermocouple, MAX31855 thermocouple-to-digital converter, Raspberry Pi running kiln-controller with a LAN dashboard tablet, and a heatsink mounted zero-crossing SSR.
• Ventilation: Fume hood interlocked to the heating element power via a DPDT switch, ensuring elements cannot fire without active ventilation.
• Passive safety & isolation: cinderblock barrier, cement flooring, and a metal gate creating an airgap isolating the kiln.
• Electrical & thermal protection: GFCI breaker for ground faults/leakage and thermal fuses for over-temperature runaways.

Software

This kiln runs jbruce12000/kiln-controller (GPL). This repo also provided wiring schematics for the system controls.

• PID time-proportioning: Drives the zero-crossing SSR via GPIO on a 2-second duty cycle with custom PID tuning derived from an initial autotune test fire.
• Dynamic ramp control: Holds firing schedules automatically if the kiln's heating rate lags by 5°F, ensuring precise thermal profiles.
• Fault detection & recovery: Triggers automated aborts on lost thermocouple signals or runaway temperatures, with state persistence for power outage recovery.
• Local web dashboard: Serves real-time telemetry (actual vs. setpoint temperature, heating rates, and energy cost estimates) over LAN to a dedicated tablet used to start runs and edit firing schedules.
• Remote alerts: Runs a background watcher daemon to monitor temperature deviations and push automated Slack notifications if conditions fall out of spec.