Exploring The Science Behind Dirty Air Filters

Obviously, if the air filters in your home HVAC system are dirty, you should change them. But exactly how dirty is dirty? [Tim Rightnour] had heard it said that if you didn’t change your filter every month or so, it could have a detrimental effect on the system’s energy consumption. Thinking that sounded suspiciously like a rumor Big Filter™ would spread to bump up their sales, he decided to collect his own data and see if there was any truth to it.

There’s a number of ways you could tackle a project like this, but [Tim] wanted to keep it relatively simple. A pressure sensor on either side of the filter should tell him how much it’s restricting the airflow, and recording the wattage of the ventilation fan would give him an idea on roughly how hard the system was working.

Now [Tim] could have got this all set up and ran it for a couple months to see the values gradually change…but who’s got time for all that? Instead, he recorded data while he switched between a clean filter, a mildly dirty one, and one that should have been taken out back and shot. Each one got 10 minutes in the system to make its impression on the sensors, including a run with no filter at all to serve as a baseline.

The findings were somewhat surprising. While there was a sizable drop in airflow when the dirty filter was installed, [Tim] found the difference between the clean filter and mildly soiled filter was almost negligible. This would seem to indicate that there’s little value in preemptively changing your filter. Counter-intuitively, he also found that the energy consumption of the ventilation fan actually dropped by nearly 50 watts when the dirty filter was installed. So much for a clean filter keeping your energy bill lower.

With today’s cheap sensors and virtually infinite storage space to hold the data from them, we’re seeing hackers find all kinds of interesting trends in everyday life. While we don’t think your air filters are spying on you, we can’t say the same for those fancy new water meters.

Karakuri Kaizen: Hacks For The Factory Floor

Anyone who has an interest and/or career in manufacturing would have heard of Kaizen, generally a concept to continuously improve your process everywhere. Under that huge umbrella is Karakuri Kaizen, encouraging workers on the factory floor to adopt a hacker mentality and improve their own work stations. It is right up our alley, manufacturer or not, making this overview by Automotive News an entertaining read.

Karakuri could be translated as “mechanism”, but implies something novel in the vein of English words gadgets, gizmos, or dare we say it: hacks. Karakuri has a history dating back to centuries-old wind-up automatons all the way to modern Rube Goldberg contraptions. When applied to modern manufacturing (as part of factory training) it encourages everyone to devise simple improvements. Each might only shave seconds off assembly time, but savings add up in due time.

Modern global manufacturing is very competitive and survival requires producing more efficiently than your competitors. While spotlights of attention may be focused on technology, automation, and construction of “alien dreadnoughts”, that focus risks neglecting gains found at a smaller and simpler scale. Kaizen means always searching for improvements, and the answer is not always more technology.

Several points in these articles asserted purely mechanical karakuri are far less expensive than automated solutions, by comparing price tags which are obviously for industrial automation equipment. We’d be curious to see if our favorite low cost tools — AVR, PIC, ESP32, and friends — would make future inroads in this area. We’ve certainly seen hacks for production at a much smaller scale.

Embedded below the break is a short video from Toyota showing off a few karakuri on their factory floor.

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Hackaday Prize Entry: Dave Thomas’ Desert Dryer

It seemed utter madness — people living in hot desert climates paying to heat air. At least it seemed that way to [David Thomas] before he modified his tumble dryer to take advantage of Arizona’s arid environment.

Hanging the wash out to dry is a time-honored solution, and should be a no-brainer in the desert. But hanging the wash takes a lot of human effort, your laundry comes back stiff, and if there’s a risk of dust storms ruining your laundry, we can see why people run the dryer indoors. But there’s no reason to waste further energy heating up your air-conditioned interior air when hot air is plentiful just a few meters away.

[David]’s modification includes removing the gas heating components of the dryer and adding an in-line filter. He explains it all in a series of videos, which at least for his model, leave no screw unturned. It’s not an expensive modification either, consisting mostly of rigid dryer hose and copious amounts of aluminum duct tape. He mentions the small fire that resulted from failing to remove the gas igniter, so consider yourself warned. The intake filter and box were originally intended for a house air-conditioning system, and required only minimal modifications.

This is a great build, being both cheap and easy to implement as well as being environmentally friendly without requiring a drastic change to [David]’s lifestyle. It makes us wish we had a similar endless supply of hot air.

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Energy Efficient Fridge Hack

Green_Freezer

We’ve already covered a pipe bomb mini-fridge this week, but inventor [Tom Chalko] provides us with today’s fridge hack. He noticed that chest-style (laying down, see above) freezers were more energy efficient when compared to normal stand up refrigerators at the same size, despite the colder temperatures involved. This is largely due to the fact that these chest-style freezers keep cold air in like water in a bowl, even if the lid is open. He has written a very thorough report on his findings (pdf), as well as a detailed walk through of the manageable task of converting a chest-style freezer into a chest-style fridge. In the end, his fridge only used 103 Wh of electricity on the first day to reach and maintain between 4° and 7° C (39° to 45° F), and he noted that 30% of that was just getting it up to temperature. After that, the fridge only turned on for roughly 90 seconds an hour, making it a very quiet fridge as well.