Fogscreen Project

[absolom7691]

So, what do you do with 10,000 drinking straws, a box full of Nidec fans, some ultrasonic foggers, and elbow grease? You make a fogscreen, of course! I have been planning this for a while but didn't know a good way to go about it. Trying to get any information on how the professional screens are knocked together is pretty much out of the question. Being the Halloween nut that I am, I visit a few Halloween DIY pages now and again and came across a decent DIY fog screen found here: http://usersites.horrorfind.com/home...creen2010.html. Now, I can spot 5 huge design flaws that I hope to correct with mine. His seems to be working decently, given the huge flaws that it has.

1. His is using what looks like only a 1/2" tall laminar matrix; I am using 7 3/4" drinking straws for a taller matrix
2. His is only using about 5 muffin fans total; I have 20 at my disposal.
3. The biggest flaw is that he doesnt really have a laminar flow, he has three. He separated each section with a bit of plywood. At that point, he might as well have just shut off the outer fans and just let the center do its work; Mine will have one continuous sheet with fog in the middle moving within the same laminar flow of air. I'll also be using a speed control on the fans to fine tune the airflow.
4. He has too little fog, which he acknowledged and I can see why, those foggers ain't cheap; Mine will be using two units for a total of 24 20mm transducers or 6000 mL of water per hour. I am also constructing it so that if 2 units aren't enough, I can add a third easily.
5. His only has an "effective" 6" of front to back laminar flow. Mine will be 10.5".

I think I can achieve decent results based on the improvements I will be incorporating into mine. If I can get about 4~5' of laminar fog flow, I will be more than thrilled.

This is what I have gotten done thus far. I have about 2200 straws laid down currently. I finally found something as tedious as widing a tesla coil secondary!

[Stiffler]

That's pretty awesome!!! I look forward to seeing the results.

[mixedgas]

Steiner and Matins on ebay, sells raw ultrasonic foggers of unknown quality, I have bought decent piezos off them in the past.

Steve

[absolom7691]

Steiner and Matins on ebay, sells raw ultrasonic foggers of unknown quality, I have bought decent piezos off them in the past.

Thank you for the info, Steve. I am definitely going to check that out. The 12 disc units are $200 from mainlandmart.com or I can buy bulk from China for $30 a unit, but I would need to order a pallet of 50. I am not looking to get into the ultrasonic fogger market so, your info may save me a bundle.

That's pretty awesome!!! I look forward to seeing the results.

Thanks. Me too. Unfortunately, it might be a weekend of two before I get it done. Laying down the straws is going much faster than I thought it would but even then, I am looking at about another 20 hours for the rest of them!

[mixedgas]

http://www.steminc.com/piezo/PZ_Mist...p?PZ_Type=MIST GENERATION TRANSDUCER&PZ_SM_MODEL=SMUTK1660RS111

350 cc a hour. 1/3rd litre. Why do I have a feeling that is marginal.


Hit the rest of the web site, you might find something to adapt.

Steve

[absolom7691]

22 layers of straws at about 180 straws per layer, almost 4,000 straws so far. Letting sit out in the sun and wind to help the silicone cure before I continue.



These Nidecs are way overkill for what I need... 5300RPM 220CFM. I don't need anywhere near that kind of airflow which is why I will be using a speed control. The fans were only $1 each so, it was a no-brainer. Using this many will also give me a lot of flexibility for fine tuning. They are also quite loud at full speed (63db) so, I am hoping that using a lot of them will enable me to run them at 1/2 speed or less to quiet everything down. During initial testing, I ran one at full 12V and it felt like it wanted to fly and also sounded like a jet turbine spinning up! 6V seemed to move a lot of air and the noise level was tolerable so, I may be in that range. 5V seemed a little weak but very very quiet and still moved some air. 4V would barely start the fan, but it did spin up. I am guessing that I will be running in the 5.5V~6.5V range. I will need to do more testing when I get the rest of this knocked together.

EDIT: These are 4 wire fans, I can run a PWM signal generator to adjust speed. I can run them as slow as I want! I just need to build a 555 circuit now.

[absolom7691]

I threw together a quick and dirty speed controller for my fans. I wasn't sure how much demand I was going to put on the 555. I'll be running a total of 14 fans on one of the controllers so a test was necessary. I wasn't able to run the fans at peak while videoing mainly because I couldn't hold them down. At full steam, these things will push themselves across the desk. At full, 2 fans were only pulling 4mA off of the 555. Considering a 555 can supply up to 200mA, I have nothing to worry about. At max, the fans draw about 2.6A each off the PSU. With 18 fans total, I should be fine with a 600 watt ATX PSU especially since I would never need to run them anywhere near max speed. I doubt I will even need to run them at 50%.

Progress is slow due to work demands but it is coming along!

[absolom7691]

Foggers arrived yesterday. I was able to negotiate a deal for ordering 4 of them. This weekend, I am going to start testing fog delivery methods.

[jammah]

Cool project! super interested thanks for sharing

[absolom7691]

I finally got all of the straws laid down. I did some flow testing tonight to test out different filter ideas to smooth out the air and eliminate hots spots. After firing it up with no filtering in place, the hot spots were of abundance. If I moved my hand across the entirity of the unit, I could easily tell where each fan stopped and the next began. After trying a few different materials, I finally happened upon a filter that seemed to work well and eliminated the hot spots (from what I could tell). I ended up using some fiberglass AC filter held down with window screen. I don't have any kind of air flow tester so I am using a small piece of paper and moving it across the unit. If it bends more at any point, then I know I have foune a hot spot. The real test will come when I actually get fog flowing through the unit. Hopefully then, I will be able to see if any part of the unit is pushing more or less air at a different speed. It is coming along, slowly....