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Fume Extractor Mod

Fume Extractor Mod



Table of Contents

Fume Extractor Mod

What and Why

Some time ago I bought a Knokoo FES150W fume extractor to use while soldering, especially when working under my microscope.

Overall I am very happy with it. I have no way to test the filtration of the unit, but the suction is strong enough to be able to work a comfortable distance away from the end of the flexible arm, and I don't notice any fumes rising directly towards my face. Also, the smell in the room after an extended soldering session is much less than before.

It is, however, not the quietest unit. I don't mind the noise while I am working, but would rather only quickly have it run while I am actually soldering. I found having to reach under my desk to turn the dial (or trying to do it with my foot) rather annoying, so I decided to design a small mod that would allow me to control the unit with a foot pedal.

Design

Because the unit goes into standby when the power-dial on the front is turned to 0, the easiest way to turn of the unit is to simply cut the 5V supply to the potentiometer making the unit think it has been turned down. This way the custom board can also simply be powered from the same 5V.

I designed a small PCB with a PIC12F1572 to handle all this.

By pressing the foot pedal once, the extractor will run for a set duration controlled by a potentiometer and automatically turn off after.

By pressing the pedal twice, the extract will run until the pedal is pressed again.

An additional LED blinks while in timer mode, or remains on while running indefinitely.

If no pedal is attached, the unit will function normally.


Installation Reference

Once the PCB is assembled and programmed, it can easily be mounted next to the actual PCB:



A short 4-pin to 3-pin JST XH cable must be made to connect the board to the main PCB:



The 1/4" jack for the pedal, status LED, and timer potentiometer are must be connected to the board with an 8-pin JST XH cable:



If the 1/4" jack does not have a switch, tie PEDC to GND (for example POT-). In this case the unit will not return to normal operation when no pedal is connected.

The timer potentiometer can be replaced by populating R6 and R7. In this case the timer will be fixed to approximately (15) * (R6 / (R6 * R7)) minutes.

Possible Improvements

I am currently working on a JBC-Compatible soldering station. If that works out I will probably add a second input to allow the soldering station to automatically turn the extractor on while I am soldering.

The easiest method would probably be a second 1/4" input that simply overrides the current pedal/timer state and turns the extract on while it is active.

Instead of using a 3-pin connector for the connection to the main board, a 4-pin would make a lot more sense. That way a 4-pin to 4-pin cable could be used.