Make:

Step 4 : Cut & Mark the openings (Wear Safety Glasses!)

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.

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

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

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


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


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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Good demonstration of how to use a 7812, but 1/3 of the battery power is being turned into heat in the 7812. This raises a number of questions. Would the fan run acceptably on just 9 volts? (No battery power wasted.) Would it be damaged if you gave it 18 volts? (Quite possibly, but we don't really know, and if not, it would run nice and fast.) Of course, a high-efficiency switching regulator would be too complicated for this type of project. But let's keep thinking...

Of course, it's quite possible the designer tried these things and concluded that the design published here really is the best.

forgo the 7812 and use 2AA & one 9V
1.5V x 2 + 9V =12V

Posted by: Marc de Vinck on April 2, 2008 at 5:55 AM

@MC

9 Volt was not strong enough, I tried it.
18 Volts seemed too much (but I really don't know)

Posted by: Marc de Vinck on April 2, 2008 at 6:58 AM

@Dill***

True, or I could use photo batteries that are 12v, but I wanted to make a little project using the 7812. I ran mine for hours and had almost no heat, and the fan still runs strong.

beautiful project, and extremely useful. Much nicer than the comp fan I have hooked up to a computer psu.

Posted by: Marc de Vinck on April 2, 2008 at 6:40 PM

@knotlinks

Thanks! There will more in the future.

If you happen to make one....Please send me a picture!

The price of a hobby fume extractor is much cheaper than $100, can move a lot more air, and wouldn't require one to replace batteries (example: http://www.mcmelectronics.com/product/21-7960).

but anyway I think this is a very nice presentable package, good for small jobs.

Posted by: Marc de Vinck on April 3, 2008 at 6:02 AM

@jproach

That one is really cheap!

But the "average" price is still about $100.

I scoured the web trying to find a site that explained how to determine what battery power I needed to run a case fan, so I am thrilled to find yours and I have a few questions for you.

1) About how long will the fan run on the 2 9volt batteries?

2) Will rechargeable batteries work just as well?

3) I know it is long, but please bear with me!

My "project" is I want to create a smart fan...that can sense the temperature and turn on when the temperature drops below the desired temp, and turn off when the temp exceeds the set temp...much like a household thermostat. There are 2 wrinkles to my plan:

1) Rather than connect the "thermostat" to the house, I want to connect it to a fan, much like the one you have here. This hurdle seems small enough to me. If I used a thermostat or something similar, the electronics and the existing brains would act as my switch and it can manage power to my fan (provided I dont have power conversion problems which you may wish to warn me of).

2) Any ordinary household thermostat wont do, because the temperatures I want to register are between 100 and 800 degrees farenheit and most household thermostats only register 90~100 degrees F. To overcome this, I considered taking a thermostat from an oven, since it is designed to handle the higher temperatures, and still in many ways acts like a household thermostat in that it can manage the provision of electricity to maintain temperature.

Do you have any thoughts or suggestions on this? I'm really interested, but I know nothing about engineering and electronics, etc. I just want to find a cheap way to manage the temperature of my BBQ grill by managing airflow. Similar systems online sell for $200+ and I'm hoping to build my own for much less. Can it be done?

Thanks for your patience and ideas!

Posted by: Marc de Vinck on April 7, 2008 at 12:52 PM

@Adam,

For your purpose, I would run it from (1) 9 volt. I needed more "juice" to get the airflow through the filter, which you don't need. That will eliminate the need for the 7812 or a switching regulator. Check Google for thermostat circuits, temperature circuits, etc....there are a lot online.

Rechargeable batteries have a lower nominal voltage. Figure out the circuit prior to making a battery decision. Since space will not be an issue (Heat will!) I would suggest using other types of batteries.

Good luck, and if you make one.....send us a link so we care share it with our readers.

What's a good/cheap/easy source for the Activated Carbon filters and the screen?

Thanks.

Posted by: Marc de Vinck on April 13, 2008 at 9:04 PM

@Lincoln

The screen can be purchased at any craft store (I paid about $2 for enough to make about 50) or Home Depot. Better yet, salvage from anything with a screen or perforated metal.The filter can be found online, (Amazon, any electronics supply stores) look for replacement filters. You can get them really cheap, and 1 filter is enough to make 6 -10 mini fume extractors.

How about taking apart a 9v and using two extra cells out of it so you get 12v. Just keep the extra 4 for the next time you change the batteries.

Why not run it on a car battery?

Seriously though, great how-to!

Posted by: Marc de Vinck on April 26, 2008 at 7:10 AM

@Eli

Great idea! - Now try it out and send me an email w/link to pictures!

@Anonymous

Car battery? That would be a good idea for a bench version. It certainly would last a long time!

Cant you just use a 12v wall wart?

Posted by: Marc de Vinck on June 4, 2008 at 10:38 AM

You sure can, but the portability is really handy.

I Have a bunch of 120mm case fans, I imagine that, although it would be bigger, it would probably work better. Now to find a box that fits it nicely.

Sure, I'll be loosing the portability factor, since I'll probably rub it off a AC-DC adapter anyway, but I'm not worried about portablity, I just need to stop soldering without one of these things!

Posted by: Marc de Vinck on June 19, 2008 at 6:01 AM

I'm glad this inspired you to add some safety to your lab.

I think 1 of your fans would be enough, maybe 2?.....mine is tiny and it works great. If you make one, which I hope you do, send me a link to some pictures!

How long will the batteries will actually last?

How about USB powered? Id rather have it be USB powered since i work next to my computer and have the option of using a battery or not. thanks

Posted by: Marc de Vinck on August 6, 2008 at 11:23 AM

@Sil3ntP8nd8

You can calculate the time (roughly) if you know the maH of the batteries and the specs of the fan. (you lose a lot due to heat of the 7812) All I can say is mine lasts a long time!

I would look for a 5 Volt fan and goggle "usb wires". You should be able to hook it up fairly easily. The main problem will be a 5 Volt fan may not be strong enough to suck the smoke through the carbon filter. That is why I went with the 12 volt system.

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