DC Fan modification

Pommie said:

Here in Australia the room fans are super cheap (approx US$10) and made in China. Or super expensive (approx US$250) made by Dyson. .

Mike.

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The former is a made by Die-Soon.

Yeah, my room fans are the cheap ones. Right now i undervolted a Breeze DF-001A, its 44W, 40cm blades and no data on cfm. It has 3 different speeds but its insane that almost all use almost the same elecitricity. Its like speed 1 is something like35W, speed 2 is like 40W and speed 3 is like 44W. So i am guessing they are using resistors of some kind and some power is wasted as heat.

Maybe i should tell you why i need this fans to be efficient. I use 2 of them, 1 of them is to dry my clothes on a hanger faster and 1 of them i use as wall unit to blow cold air into my place in the summer nights. It works magic but it kind of feels stupid that those 2 fans use more electricity than my workstation computer. And since pc fans use so little electricity and i have tons of them at home, i was wondering if i could somehow use that to my advantage. Ideas here are:

1) 9 small pc fans instead of 1 big desktop fan, hoping to get more bang per electricity usage
2) put the blades of a big desktop fan on my 12V 1A pc fan and hope it will not burn out trying to turn the big blades
3) Maybe something else ?

SentinelAeon said:

1) 9 small pc fans instead of 1 big desktop fan, hoping to get more bang per electricity usage

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You've measured the usage of your big fan, do the same for your small ones.

A quick look around shows 90mm fans that use from as little as 1W each to some that draw 8W; you need to know what yours draw and do the math.

Don't forget to measure the power used by whatever power supply you are going to use to get your 12V.

Will do that. More problematic will be to measure the actual airflow. The roomfan at 10W i can barely feel the breeze but its huge so it sums up i guess. The little fans even on quiet setting, u can definetly feel it but its much much smaller. Will do some testing.

Btw, is there any cheap and easy way to measure air moved by fans of different size ? For instance, connect the fan to the tube with some kind of gauge that will spin depending on the speed ? It doesnt have to be super accurate. Its just to compare different fans. I would simply use a custom made tunel to connect fans that are to big or to small for the gauge. Or maybe i dont even need a tunnel, just a gauge to put in fron of the fan. If i get the speed of air, i just need to multiply it by size of fan and i get the approximate cfm.

SentinelAeon said:

is there any cheap and easy way to measure air moved by fans of different size ?

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You could try a cheap anemometer. Probably cheaper (second-hand) on ebay.