Heat Gun Controller: Temperature and Airflow Regulation

A heat gun controller with electronic temperature and airflow regulation turns a basic heat gun into a precision SMD rework tool. By adding thermocouple feedback and PID control, you get stable, adjustable temperatures from 100°C to 480°C — essential for PCB rework, shrink tubing, and plastic welding. This guide covers building a controlled hot air station.

What Is a Heat Gun Controller?

Basic heat guns from hardware shops (₹500-1,500) have only high/low settings. Adding electronic control gives you: precise temperature selection, stable output regardless of ambient conditions, adjustable airflow independent of temperature, and the ability to follow reflow profiles for SMD rework.

Temperature and Airflow Regulation

A hot air station has two independent controls:

• Temperature: Heater element power (typically 300-700W) regulated by PID controller with thermocouple feedback at the nozzle exit
• Airflow: Fan/blower speed controlled by voltage regulation (TRIAC dimmer or PWM)

For SMD rework, typical settings: 350-400°C at low airflow for desoldering. Higher airflow for heat shrink and general heating.

Components for the Build

• Heat gun element (from a cheap 1500-2000W heat gun, ₹500-800)
• K-type thermocouple + MAX6675 module for temperature sensing
• Arduino Uno for PID control
• SSR 25A for heater switching (AC load)
• TRIAC dimmer module for fan speed control
• OLED display and rotary encoder for interface
• Zero-cross detector for clean TRIAC switching

PID Temperature Control Circuit

The thermocouple mounts at the nozzle exit (use a high-temperature thermocouple rated for 600°C+). The MAX6675 reads temperature and feeds it to the Arduino PID loop. The PID output controls an SSR that switches the AC heating element. Window-based PWM with a 2-second period gives smooth, proportional control.

Airflow Control with TRIAC Dimmer

The fan inside the heat gun is an AC blower. Control its speed with a TRIAC dimmer (phase-angle control). A zero-cross detector synchronises the TRIAC firing with the AC waveform for smooth, buzz-free speed control. Lower fan speed = more concentrated heat, higher speed = wider, cooler airflow.

Building the Handheld Unit

If modifying a commercial heat gun, remove the original thermostat and switch. Wire the heating element through the SSR and the fan through the TRIAC dimmer. Mount the Arduino controller in a separate desk unit connected to the heat gun via a flexible cable. This keeps the handheld unit lightweight.

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Safety Precautions

• Heat guns produce temperatures above 400°C — severe burn hazard
• Never point at flammable materials
• The heating element draws 1,500-2,000W — ensure wiring and connectors are rated accordingly
• SSR MUST have a heat sink — it dissipates 10-20W switching high currents
• Allow the element to cool with the fan running before disconnecting power