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Old 05-16-2007, 02:12 PM   #1 (permalink)
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JT mask fans with speed control

Well, I made this a year ago and so far it's worked extremely well. I figured I'd re-post this from my PB Nation post for those that always wonder what that box is sticking out the side of my mask. By the way, I never notice it, it's not that heavy at all.


OKay, like many of you I wear eyeglasses, which can (will) fog up. So far my fan modifications have worked very well for me. This project was my solution and hopefully some of you will find things here you can use.

This is more of a working prototype and not a finished design, I'll redesign it sometime...

I have a stock JT mask fan but it has a couple of design flaws which really annoyed me. Since the fan was only on one side, and it was a wimpy fan at that, only one side of my eyeglasses would be clear. The other thing was that the battery was internal and you had to remove the entire unit to change the single battery. Anyone who has changed one of these JT mask fans knows taking it on and off is a serious pain in the ... fingers.

I decided to upgrade it all. I figured that 2 big fans, running slowly, would move a lot of air and be quiet as well (which turned out to be the case). One of the problems with muffin fans is that they require a certain voltage or they wont turn. What you need is an actual speed control circuit. Luckily such circuits are quite common. What I used is a circuit called a "Pulse Width Modulator". If you Google that you'll find lots of different designs. Basically, it's like turning a power switch on and off over and over. The faster you turn it on and off, the faster the motors, or fans, will spin.

I should mention that since a Pulse Width Modulator works by turning the juice on and off, it also will draw less current the slower it goes. If it's only on 50% of the time, it will draw a little more than half of what it would if there was no speed control at all and the fans were turned full on. Keep this in mind when figuring out how long batteries will last.

Originally I was going to build mine from scratch, but when I was ordering parts from All Electronics I ran across a circuit with board and parts for only $3.50:

Speed Control Circuit

I ordered the other parts I needed for this project from them too ... mainly the fans. I ordered both 25mm and 20mm fans. At $4 ish a piece, what the hell. All Electronics is cheap. All the parts I used in the project only cost me about $15.

(Oh, by the way, if you do something like this, unless you want to spend 3 - 5 times the money, don't go to Radio Shack. Yesterdays technology at tomorrows prices.)

I used the biggest fans I could shoehorn in. I used the 25mm fans and I had to do a lot of dremeling to get enough material off to fit them in. If I did this project again, I'd probably use the 20mm fans since they'll fit no problem. I also use an external battery pack now so I don't have to take my entire mask apart to change batteries.

K, down to the short strokes ...

Step 1: Build the circuit and an enclosure

Pretty straightforward, solder all the parts to the board and lay them down so they can fit inside a small box;



The speed of the fans is controlled by that small trim pot you see the tool turning. You can easily substitute an external trim pot (think volume knob) so you can change the speed of the fans on the fly. I wanted to make it as small as possible though, and so far it hasn't been a problem. However, if you do it my way you might want to use the proper plastic tool ...



... so you don't short out anything.

For the enclosure I built my own from sheet plastic you get at model stores. Very easy to use and responds well to heat, and glues well. I made a template out of paper, then cut out the form from the plastic sheet with scissors;



To get the sharp bends I scored one side with a soldering iron, and then used heat on the other side as I was bending it;



All in all it came out pretty good ... although I have to admit I did it twice to get it just right. If you don't do it right you'll break the plastic at the seams.

Mount the board in the box;



Hot glue it all up and use a zip tie to keep the wires from being pulled out;



Solder it to a battery pack and glue it all up;



Step 2: Mounting Fans Inside The Housing

As I stated before, in order to fit 25mm fans inside a stock JT housing you have to shave off plastic from all over the place. I had to belt sand off two corners from each fan ...




... and also dremel off plastic from the housing itself. Whoever made the housings for JT was lousy ... the thickness of the plastic varied greatly everywhere. Luckily you can use the amount of light you can see through the plastic to tell how thick the plastic is when you're grinding it off. If you do it my way and decide to paint it another color, shave off the plastic first before painting it.

I mounted the fans to the back plate with double sided 3M tape;



(This tape is VERY expensive, but it's great to have around. It's used to stick trim onto cars. I used it to years ago to mount surround sound speakers to my TV and to mount a 12 disk CD changer to the back wall of my truck. It sticks like crazy)

Trimmed it up a little;



Screwed it into the housing (you can see all the dremel marks);



And finally super and hot glued it all to make it air tight;



One of the things I wanted to do to make the fans quiet is to keep them up as far away from the top of the mask as I could. Also, the reason I made it air tight is to separate the area the masks draw air from, from the exhaust. As they sit now the fans are not touching the top of the mask at all, and draw air from as large an area as possible.

(By the way, between the double sided tape, super glue, and hot glue, this is all incredibly strong. Did I mention that I want to avoid taking this off?)

Here is a picture showing the difference between a 25mm fan and a 20mm fan. As you can see, the 20m fans would fit no problemo;



Step 3: Mounting To The Mask

The rest is pretty easy. Mount the fan unit to the mask;



Solder it to the battery pack and speed control. Put an old sock over it;



Use some Velcro straps to attach the battery pack unit to the mask;




Use a couple of zip ties to tidy things up;



And there you have it;



Voila!
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Old 05-16-2007, 02:47 PM   #2 (permalink)
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Nice mod!

You might even get away with mounting that controller a littel more compact, surface mounting the switch and encasing the whole thing in epoxy.

If i still used JT masks, i would be all over this mod (insert plug for Vents here)
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Old 05-16-2007, 04:23 PM   #3 (permalink)
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I thought about making it more compact, probably by directly connecting all the components and shoehorning them into the shroud itself. But, if it ain't broke, don't fix it.
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If your glasses fog up and you want to make your own mask fans, here's how;




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Old 05-16-2007, 04:47 PM   #4 (permalink)
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Well its obviously broke if you fixed it so well already
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Old 11-10-2012, 06:04 PM   #5 (permalink)
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I hate to dig up old topics, but do you think you could just swap out a 20mm fan for the standard JT fan and it would work better? For now the JT fan works just fine but man is it loud
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Old 11-10-2012, 06:14 PM   #6 (permalink)
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Reign, pull of the prop and put a couple of drops of oil on the motor shaft then turn on the fan. it will help to quiet the fans.
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Old 12-22-2014, 03:05 AM   #7 (permalink)
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Quote:
Originally Posted by Washington reign View Post
I hate to dig up old topics, but do you think you could just swap out a 20mm fan for the standard JT fan and it would work better? For now the JT fan works just fine but man is it loud
Sorry I just noticed this...I've only played twice since you posted this and haven't been on much.

20mm fans will fit great, but, you'll have to use four AAA or AA batteries, so you'll have to use an external box still. See my sig for updated links to cheap parts.
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