General > General Technical Chat
HEPA filters and fans
engineheat:
--- Quote ---It says 13.8V max in the datasheet, you want a buck regulator.
You can get an adjustable buck module for <$2 online. Then that gives you the ability to throttle down the fan voltage as well.
--- End quote ---
Thanks. I'm pretty new to using buck converters. Can you provide an example of something that'll satisfy my need? When choosing a buck converter, you gotta find one that match your input voltage range, output voltage range, and the wattage of the application right?
https://www.amazon.com/Converter-DROK-Transformer-Regulator-Stabilizer/dp/B00JUFJ1GA
I found one above on Amazon but it seems like a poor quality one that'll break easily. It says output current : 2A so that seems to be the limiting factor regardless of output voltage?
james_s:
I've used these quite a few times, they're cheap and work fine.
https://www.ebay.com/itm/332711109230
The IC is not really what it says it is on the ones I have, it runs at the wrong frequency but it works fine. If you need more current you can easily get similar regulators that are rated for 5, 10 amps or more. I wouldn't run one of those Chinese modules past about 60-70% rated current though.
engineheat:
--- Quote from: thm_w on April 10, 2023, 09:38:19 pm ---
--- Quote from: engineheat on April 09, 2023, 10:16:53 pm ---I'm looking at this fan for the PAPR application
https://www.delta-fan.com/products/BFB0712HD.html
But it's a 12V (rated) DC Brushless fan. I currently only have some 18V batteries. Is it problematic to run it at 18V or should I get a buck converter?
Thanks
--- End quote ---
It says 13.8V max in the datasheet, you want a buck regulator.
You can get an adjustable buck module for <$2 online. Then that gives you the ability to throttle down the fan voltage as well.
--- End quote ---
If I understand correctly, you can vary the speed of a DC fan such as the Delta fan above with PWM right? This one have 2 wires.
Because I read there's also "PWM" fans with a dedicated wire for PWM.
engineheat:
--- Quote from: james_s on April 12, 2023, 06:28:07 am ---I've used these quite a few times, they're cheap and work fine.
https://www.ebay.com/itm/332711109230
The IC is not really what it says it is on the ones I have, it runs at the wrong frequency but it works fine. If you need more current you can easily get similar regulators that are rated for 5, 10 amps or more. I wouldn't run one of those Chinese modules past about 60-70% rated current though.
--- End quote ---
Do you know how efficient those buck converters tend to be?
engineheat:
--- Quote from: lfldp on March 26, 2023, 08:58:39 am ---
--- Quote from: engineheat on March 19, 2023, 01:57:55 am ---Hi,
I want to build a DIY air purifying system that incorporates a HEPA filter.
I'm a bit confused on the different types of fans available for filtration purposes. I know there must be sufficient air pressure.
When I tried to learn more about fans, I come across terminologies like "centrifugal" and "axial". The way I understand, axial fans are the common type that we are all familiar with, it can move lot of air but cannot generate high static pressure.
But I'm a bit fuzzy on the terms "centrifugal", "squirrel cage", "blower". Are they all pretty much the same thing? Any of those would be suitable for a HEPA filter provided the static pressure is sufficient right? Do you know what pressure is sufficient for a HEPA filter (assuming clean filter, just need a rough ballpark idea)
Thanks
--- End quote ---
hi
if you need to use hepa h13 alone then blower from air cleaner should be ok but if you want to add carbon filter then you will need at last blower with high pressure like ebm papst like this https://www.ebmpapst.com/de/en/products/blowers/gas-blowers.html only gas blowers and modiffied gas blowers have high static pressures to manage both hepa + carbon filters but they have less airflow up to 180m3/h , in soldering fume extractors like bofa or weller you have one from these gas blowers or too both connected in pararrel 180m3/h x2 = up to 360m3/h , in chinese fume extractors blowers used too but less quality
i can explain you exactly about how you count calculate valid static pressure do fan/blower pairing etc. ;)
you need both hepa h13 filter documentation paper and blower speciffication
you have speciffication of hepa filter in attachment (for example the one which you wanna buy) at first you must obtain how much airflow you need - lets say 150m3/h
1. in filter airflow chart check about how many Pa(static pressure) the filter suck trought 150m3/h speed H13 UltraMet78 with 305 305 size like you see it give around of 170 Pa at 150m3/h airflow but this is not the end of calculation !
2. the 170 Pa is static pressure generated on clean filter but you will need static pressure on dirty filter , when there will be more dirt then filter make more static pressure - how calculate this ? just count 170 Pa x 2,5 = 425 Pa (this will be final pressure drop on this hepa h13 filter) so you will need blower which can manage 425 Pa trought 150m/3h airflow ;)
3. now go to the blower speciffication and check on its chart about how much pressure drop it can manage at 150m3/h speed
and btw. from my own experiments i can tell you the blowers from cheap air cleaners should manage valid pressure drop for hepa but if you want to add some carbon filters you will need high end blower
--- End quote ---
Thanks. That was helpful.
Is it possible to use pressure sensors (manometers) to measure the pressure drop while the air purifier is in operation, that way you'll know when the pressure drop is too high and the filter needs to be changed?
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