Toaster Oven Reflow Technique

See also HotplateReflowTechnique.

Introduction

This page describes how to reflow solder surface mount printed circuits using a cheap toaster oven. It owes a great deal to Nophead's Cooking with Hydraraptor blog post.

Equipment

The toaster oven we use is this 900W one from Argos in the UK. It costs £25.

You will also need an Arduino to control it. Just about any Arduino will do; we use the Arduino Diecimila, because we happened to have a few lying about.

Finally, you need a solid-state relay so the Arduino can turn the oven on and off, and a temperature sensor that will do up to 250^oC.

We use this solid-state relay from Farnell, and a thermocouple plus thermocouple amplifier (see below). Alternatively you could use the same types of thermistors that RepRap uses for its extruders as temperature sensors - the temperatures are about the same.

Control

This is the circuit diagram of the thermocouple amplifier. IC1 is an AD595. It needs a Type K thermocouple.

The thermocouple connects to pins 1 and 14.

JP1 connects to the Arduino:

• JP1 pin 1 -> Arduino +5v.
• JP1 pin 2 -> Arduino A₀.
• JP1 pin 3 -> Arduino Ground.

The solid-state relay has four connections. To go in series with the mains live wire. The other two turn the current on and off.

The neatest thing to do with the solid-state relay is to mount it inside a mains plug patress box. Run the control wires out of the side of the box and connect them to the Arduino: + goes to the Arduino LED (D13 on an Arduino ), the other control connection goes to the Arduino ground.

Note that there is no electrical connection inside the solid-state relay between the control circuit and the mains circuit. The device is optically coupled, so there is no danger that you will get mains floeing through your Arduino (as long as you wire things up right...).

Video

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