When the article about the Mini Reflow Plate that appeared in Elektor November/December 2023, I was very taken with it. I had already built a similar project once using an old iron, but it was so bulky that it was only dug out in “the greatest need” and otherwise gathered dust on the shelf. 

So, as soon as the Gerber files for the Mini Reflow Plate were available for download, I ordered the boards and missing parts from China. I didn’t have to wait long and was quickly able to start rebuilding. The first test went thoroughly wrong, as the board of the K thermocouple sensor had an error, which led to the hot plate overheating excessively and the feet burning into the base. A new MAX6675 board had to be ordered.

Fan reflow plate main 1
Figure 1: The hot plate is attached at a safe distance with neodymium magnets.

The lesson from this first test was to use a fireproof base for the hot plate. In the workshop, I found a suitable U-shaped aluminum sheet, in which holes were drilled and tapped with M2.5 threads where the feet of the hot plate should stand. At these spots, as you can see in Figure 1, radial neodymium magnets with mounting holes were screwed in (which were also found in the workshop drawer). The chassis of the housing was assembled from leftover plywood or multiplex boards, so that there was enough space for the electronics (Figure 2).

Fan reflow plate 2
Figure 2: A spacious wooden housing for the electronics.

A Fan for Cooling!

Even with my iron application, I had found that the necessary, quick cooling of the plate after the reflow process could be a problem, and it was the same with this project. The hot plate has significantly less mass than the old iron, but this effect cannot be neglected here either.

So the Mini Reflow Plate (just like the old iron) was successfully equipped with a 5-V fan. The control is done by the Arduino Nano via a transistor driver stage. The Nano has enough free outputs, you could even add some other nice gimmicks. The fan control was also quickly added to the Arduino sketch.

 

A simple transistor driver between Arduino and fan
Figure 3: A simple transistor driver between Arduino and fan

Small Modifications

The base of the transistor was connected to pin D12 (Figure 3), because this is easily accessible on the board (Figure 4). In the definitions section of the sketch (directly under the definition of int piezo = 13; and int riscaldatore = 10;), the new sketch now has int fan = 12;. 

The transistor driver fits directly under the Arduino board
Figure 4: The transistor driver fits directly under the Arduino board

In the setup of the sketch, you set the mode of the pin: pinMode(fan, OUTPUT);, again under the pinMode(...) function call for the piezo buzzer. The fan is switched on in the cooling phase with the ordinal number 4, in the routine where the reflow functionality is managed (Gestione funzionalità Reflow). It now says:

 

faseAttuale = i;

   if (faseAttuale == 4)

      digitalWrite(fan, HIGH);   // fan on

   else

      digitalWrite(fan, LOW);    // fan off

      regolaRiscaldatore();

 

What is still missing is turning off the fan when the running process is aborted by a long key press. This is done in the reflowStop() and reflowEnd() functions:

 

void reflowStop() {

   reflowRunning = false;

   myPID.SetMode(MANUAL);    // deactivates PID

   analogWrite2(0);          // heater off

   digitalWrite(fan, LOW);   // fan off

   longBeep();

   displayClear();

}

 

void reflowEnd() {

   reflowRunning = false;

   myPID.SetMode(MANUAL);    // deactivates PID

   analogWrite2(0);          // heater off

   digitalWrite(fan, LOW);   // fan off

   endBeep();

   displayClear();

}

 

The fan was screwed onto two leftover pieces of multiplex and placed exactly above the hot plate, as can be seen in the title image.

It should also be emphasized that, of course, a three-core mains cable was used for the power supply and, after taking the photos, was also fitted with a mains switch. The protective conductor is connected to the U-profile and is thus also in contact with the hot plate and the shielding of the temperature sensor — better safe than sorry! 

Editor's Note: This article (240198-01) appears in Elektor November/December 2025.

Questions About the Fan for the Mini Reflow Plate?

If you have technical questions or feedback about this article, please contact the Elektor editorial team at editor@elektor.com.

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