How to convert 48v fan to 12v DC? - Page 1
Forum section: electronics / beginners

author: WhiteFireDragon
author_rank: Regular Contributor
timestamp: March 08, 2014, 07:35:49 am
content: Hi, I have a few high-powered fans that only work in the 48v range, I want to use it in a computer with a ATX power supply, which can only use 5v or 12v. What can I use to easily turn the 48v requirement to use the 12v from the PSU?

author: homebrew
author_rank: Frequent Contributor
timestamp: March 08, 2014, 07:42:59 am
content: Easy and cheap? Probably not ...But of course you could build a step-up converter like this one:http://www.maximintegrated.com/app-notes/index.mvp/id/911It gets you 48V@1A.Best,homebrew

author: WhiteFireDragon
author_rank: Regular Contributor
timestamp: March 08, 2014, 07:49:54 am
content: Is this considered a step up converter?http://www.amazon.com/gp/product/B00BZR9PBW/ref=as_li_ss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B00BZR9PBWInput voltage :10-32V DCOutput voltage: 35-60V DC (adjustable)Output Current: 5A (MAX)Input Current: 16A (MAX) (Please enhance heat dissipation if more than 10A)Output power: natural cooling 80W (MAX), enhance heat dissipation 120W (MAX)The high powered fan only requires 0.93A at 48v. If it's converted to 12v, does that mean the current draw is quadrupedaled to keep the same power, or is the current draw the same and power is cut down to 1/4?

author: Rerouter
author_rank: Super Contributor
timestamp: March 08, 2014, 07:52:56 am
content: it draws 4 times the current on the input, so each fan would pull a little over 4A (efficiency bites in the backside here)

author: rr100
author_rank: Frequent Contributor
timestamp: March 08, 2014, 07:57:55 am
content: - yes, that product would do nicely and you can also adjust the voltage to change fan speed (assuming your fan behaves like that).The current from 12V will be of course 4x+ (to account for loses) higher. Should be no problem for a 12V power supply.

author: WhiteFireDragon
author_rank: Regular Contributor
timestamp: March 08, 2014, 08:10:46 am
content: Thanks homebrew, Rerouter, and rr100! I'll grab one of those step up dc-dc converters.Based on the specs, would hooking up 2 fans rated for 0.93A at 48v be pushing the limits of this converter? Or should I get one for each fan?

author: SeanB
author_rank: Super Contributor
timestamp: March 08, 2014, 09:24:23 am
content: You could do 3 fans with one module with no problem, but remember that this module will need to be cooled as well by the airflow in the case so place it where some of the fan air can pass over the cooling fins of the heatsinks.

author: G7PSK
author_rank: Super Contributor
timestamp: March 08, 2014, 09:33:34 am
content: Quote from: WhiteFireDragon on March 08, 2014, 07:49:54 amYou can get those boards from china on ebay for a dollar or two.

author: WhiteFireDragon
author_rank: Regular Contributor
timestamp: March 08, 2014, 11:07:01 am
content: Quote from: G7PSK on March 08, 2014, 09:33:34 amLink? I saw a bunch on ebay, but cheapest one with same specs is this one for $8. Where are the $1 or $2 ones? And I'm not too concerned about cost anyways, as long as it's not over $15 for something this simple. I already bought the one from amazon.http://www.ebay.com/itm/271416568098

author: peter.mitchell
author_rank: Super Contributor
timestamp: March 08, 2014, 04:21:33 pm
content: Bah, just be tidy, buy a single, larger boost converter, and use it.Here is a nice looking one;ebay link, $40 US, 300W, looks well laid out, has mounting holes in the corners (IMPORTANT), has adjustable voltage if you want to use it for something else later too, i get the feeling it will be efficient and not make much heat; the PCB looks quality.

author: rr100
author_rank: Frequent Contributor
timestamp: March 08, 2014, 07:25:39 pm
content: I am not opposed to overkill, really, I check the batteries with a 6-digit multimeter and I charge batteries (and sometimes jump-start cars) with a 60A adjustable power supply. But 300W for two fans is really too much, especially that most circuits (including the one from amazon) can limit start-up spikes (we're talking about motors).

author: peter.mitchell
author_rank: Super Contributor
timestamp: March 09, 2014, 12:14:01 am
content: Quote from: rr100 on March 08, 2014, 07:25:39 pmLets put it this way, each fan uses 48v, 0.93A = 44.64W, x2 = 89.28W. 90% efficiency? (yeah right, more like 80%, but any way) 10W heat AND you're probably pushing the limits on the boost converter so you'll probably want 2 converters, and a fan. 2 converters and a fan(say $4 for a fan) and you're at $28, $12 more and you have something that doesn't spew switching noise everywhere, doesn't need a fan and is made with parts that won't die after 6 months (the output + input cap will be dead). *infomercial voice* But wait, there's more! If you call now we'll throw in a perfectly readable chinglish datasheet absolutely free!!https://dl.dropboxusercontent.com/u/677635/PS-SP12137_Ver1.0_EN.pdf

author: rr100
author_rank: Frequent Contributor
timestamp: March 10, 2014, 08:41:25 am
content: For me frankly 90W of fan power"to use it in a computer"sounds way too much. I know "computer" might mean different things and you can actually walk in some "computers" but still I assumed is something more common and the rating on the fans means in fact the maximum current drawn and the constant power is in fact way lower.

author: Rerouter
author_rank: Super Contributor
timestamp: March 10, 2014, 09:37:37 am
content: That is correct rr100, though if you try and get your way into packing significant amounts of heat generating hardware into a small box a big fan can be required just to prevent it from melting (PCB's will warp over time if you let the computer cook on its thermal throttling limit)An example of this might be an ITX gaming build,I myself only have 4 fans in my computer, 2 very low RPM and very quiet ones on my cpu heatsink, 1 quiet one on my gpu, and one built into my power supply that doesn't even turn on until you exceed 60% capacity, and even then you couldn't tell when its on, effective cooling vs brute force... (for those that want a reference, an i7-3770 cpu and HD5850 GPU)

author: EEVPiobee
author_rank: Contributor
timestamp: March 10, 2014, 09:40:22 am
content: Quote from: rr100 on March 10, 2014, 08:41:25 amI must agree with rr100.. 90w Is a lot; and if we're both talking about a standard, household pc, and you do power it from your pc's standard power supply, you won't have much left for the rest of the stuff you actually have and need in a PC to run.. (Mainboard, hard drive, DVD burner, graph card... etc)That would be WAY more convenient to get a proper 48v power supply rated at proper wattage on eBay... plus they are cheap (15$ more or less for a "Laptop style" one)This is not necessarily an elegant solution, but looking at yours... Eh it may be an option... (However if you want to make a step-up transformer just for the hick of it, or to learn something new for fun or whatever ... I totally understand !)

author: STS
author_rank: Newbie
timestamp: March 10, 2014, 11:37:07 am
content: 90W is a lot of fan for an ATX box!A lot of air that you won't be able to push out of the box, so your only option would be to use it to suck air out.All in all - WAY too much fan. Keep in mind that the average 120mm fan is less than 5W and moves around 50cfm...