How to: Candy tin fume extractor

How to: Candy tin fume extractor

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A fume extractor uses an activated carbon filter and fan to remove the smoke, and noxious fumes, created from soldering. The average price of a small hobby version is about $100, this one will run you about $10. This fume extractor will not be as effective as a larger one, but it is better than nothing, and extremely portable. Remember, always work in a well-ventilated area.

Parts you need:

(1) 7812 – Voltage regulator
(1) Candy tin
(1) Switch
(1) 40 mm case fan
(2) 9-Volt batteries
(2) “Cheap” 9V battery connectors (see step 2 & 3)
(2) Pieces of screen
(1) Piece of activated carbon filter
Some heat shrink tubing
A few inches of Wire
Rosin core solder
Miscellaneous screws and washers
Paint (optional)

Tools you need:

Soldering iron
Dremel with cutoff wheel
Drill & small drill-bits
Fine tip marker
Various Screwdrivers
Wire cutters
Safety glasses

Step 1 : Build the circuit


I decided that that a quick mock-up might be a good idea. I am glad I did. At first, I thought that running the case fan off of just (1) 9-Volt would provide adequate power. In the end I decided that 12 volts “sucked” better, and in this case it’s a good thing.

The final circuit uses a simple switch, (2) 9 volt batteries, a 40mm case fan, and a 7812 voltage regulator. The 7812 takes voltage from the (2) 9-Volts that are wired in series and steps the voltage down from 18-Volts to 12-Volts, which is what the fan requires.

Step 2 : Solder components
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Notice the battery connectors; they are the flexible vinyl version, not the hard plastic type. This allows them to easily fit in the case.
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This is a very simple circuit. Solder it according to the diagram, making sure to attach the component leads to the 7812 properly. Don’t forget to use heat shrink tubing on the connections, this is in a metal box…..metal conducts electricity!

Step 3 : Make sure it all fits
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Everything can be stuffed into the tin, but make sure you use the cheap kind of 9 volt connectors. The cheap ones are the kind made of vinyl, not rigid plastic. The difference in thickness is minimal, but it is enough to stop you from putting both 9 volts in the case.Step 4 : Cut & Mark the openings (Wear Safety Glasses!)
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I used a marker and a paper template for the fan openings. The openings are 35mm square. I marked the opening for the switch at the same time. Then I cut all the openings with a Dremel tool and cutoff wheel (Wear safety glasses!). Next I marked and drilled the (2) holes for the switch screws and (1) hole for the regulator.
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After you cut the first fan hole, close the box and use the 35 mm square paper template to align the second hole. Just “eyeball” the placement. In reality it isn’t that crucial to have them exact. There is room for error.

Step 5 : Paint
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I decided to paint the tin this time, unlike my plain RuntyBoost. I chose a nice red Krylon paint. I hot glued a scrap piece of wood to the inside, so I could hold it while I spray painted it. Two quick coats and I think it looks good. Krylon paint is fairly toxic and flammable, so paint it outside and away from everything!

Step 6 : Attach the regulator and switch
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First screw in the 7812 using some washers and a screw to space it from the side of the tin. I used a #6-32 screw and (1) washers to keep it from the edge, but you can use anything that fits. The screws and washer will also act as a heat sink. Finally, screw in the switch

Step 7 : Add the screens and filter


Here you can see the screen-filter-fan-screen sandwich. The screens are 50 mm square & the filter is 40mm square. You can buy replacement filters for the commercial extractors at a reasonable price. Next, just hot glue, or epoxy, the corners of the screens down, and sandwich the filter and fan in-between. Compression will ultimately hold it all together.

Step 8 : Admire your work
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All done! I am happy with how it came out, but it definitely needs some graphics to spruce it up. Any suggestions?
Step 9 : Test
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I have run mine continuously for hours and have had no heat buildup from the 7812 and the fan is still running strong. It seems to work quite well, although it is no replacement for a large fume extractor, it will come in handy for small projects. Remember, follow all safety guidelines when soldering, and work in a well-ventilated room, even if you have a fume extractor.

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