Circuits with fans, should be pretty easy.

  • Thread starter Kirro
  • Start date
  • Tags
    Circuits
In summary, the conversation revolved around trying to connect two 12V fans to two USB ports, with concerns about damaging the computer and finding a way to power the fans with the limited 5V output of the USB ports. After some discussion and suggestions, it was determined that using a DC-DC converter or finding 5V fans would be the best solution. The conversation also touched on the possibility of using a 9V battery to power the fans. There were some discrepancies in the fan specifications, with one person mentioning a fan that required 230 amps, which seemed unlikely. In conclusion, it was recommended to do more research and possibly consult an expert in order to find a suitable solution for powering the fans.
  • #36
National Semiconductor also has a (relatively) powerful online power supply tool called WEBENCH:

http://webench.national.com/appinfo/power/webench/index.cgi [Broken]

- Warren
 
Last edited by a moderator:
Engineering news on Phys.org
  • #37
chroot said:
National Semiconductor also has a (relatively) powerful online power supply tool called WEBENCH

Interesting stuff here... I was checking out the LM3224:

InputMin Voltage 2.7 Volt
InputMax Voltage 7 Volt
Adjustable Output Yes
Output Range Vin to 20V

I'm guessing that's the sort of DC-DC converter I'm looking for.

Looks good on the search page however when I add it to my order it reads $4.95 for the part, $5 for the handling, and then $2 for the shipping? Is that possible? I'm really even sure that is the same part that I selected on the search page because the minimum order is 1000 units. (lol)

Similarly, http://www.national.com/pf//LM/LM2588.html [Broken] also looks good, however.. at the bottom of the page is 24 different variations of the same chip. I know I want a 12v one but there are 3 of those.As a side note, how big are these things? What do they look like? There aren't any real pictures on the website other than the circuits.
 
Last edited by a moderator:
  • #38
berkeman said:
http://www.national.com/an/AN/AN-1066.pdf#page=1 [Broken]

You design your own boost converter for a couple of dollars, and include that in the overall design. (I think I mentioned this already, but it could have been in a different thread...) A DC-DC converter is basically a constant power converter, with some efficiency loss. So the input current will be more for your boost application than the output current. That should be part of your calculations for the current demand that you will place on the USB port.

hmm, I read through that PDF and found it pretty interesting. However, I don't think I'd be able to make a working circuit after reading through that.


[sorry for double post]
 
Last edited by a moderator:
  • #39
Kirro said:
Looks good on the search page however when I add it to my order it reads $4.95 for the part, $5 for the handling, and then $2 for the shipping? Is that possible? I'm really even sure that is the same part that I selected on the search page because the minimum order is 1000 units. (lol)

You're not going to want to order directly from the manufacturer. The manufacturer only deals directly with big contracts, like Sony. National Semiconductor is not interested in dealing with you directly unless you're buying a significant number of devices. For small orders, you want to go through a distributor, like DigiKey or Arrow or Newark.

DigiKey, for example, will sell you a single unit for a price of $4.53.

As a side note, how big are these things? What do they look like? There aren't any real pictures on the website other than the circuits.

Look at the datasheet. All datasheets will include a package mechanical drawing, often on the last page. The LM3224, for example, is an 8-lead surface mount package. (You might find these difficult to solder, unfortunately. They're meant to be soldered by automatic machinery.)

- Warren
 
  • #40
Danger said:
Hmm... that's unusual. I routinely run DC motors at reduced voltage with no problems. Yours must have a really high starting resistance.
Likely a brushless DC fan those aren't quite as flexible as straight motor.
 
  • #41
Kirro said:
hmm, I read through that PDF and found it pretty interesting. However, I don't think I'd be able to make a working circuit after reading through that.
As long as you are thinking of ordering parts.
Why not just get a sutible fan instead.
Here is an example
http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=259&M=KDE0504PFS2-8 [Broken]
Lots of other choices

5vdc brushless <.200 ma
And less than $7 plus whatever they want for shipping.

Also you might want to do some calcs on just what you really need for airflow.
 
Last edited by a moderator:
  • #42
NoTime said:
Likely a brushless DC fan those aren't quite as flexible as straight motor.
Ahhh... I don't have any experience with those. Good point.
 
  • #43
Sorry, I stopped getting notified of new posts for some reason.

NoTime, those fans are PERFECT.:!) :!)

As far as calculating airflow goes.. I'm not really sure how much airflow I'm going to need to cool off the heatsink. I am fairly familiar with about how much air a certain rpm will give with various types of fan blades. I would estimate I need something around 4K-5K rpm to achieve my goal with minimal noise.

Thanks very much for the link!
 
  • #44
Every site I've found that carry these fans have minimum orders of 200+ or handling fees of $15 + shipping. :grumpy: :grumpy:
 
  • #45
Kirro said:
Every site I've found that carry these fans have minimum orders of 200+ or handling fees of $15 + shipping. :grumpy: :grumpy:
?? Where are you looking ??
Digikey is only $5 handling for orders < $25.
$0 if > $25. And the will sell you just 1.

Search the catlog there is probably something else you need to actually finish the project.
Or just order 4 fans :smile:
 
  • #46
... You're exactly right. I'm not sure what I was doing before...

I checked out other items they have and I was very excited to see some of their other products! They've got shrink wrap tubing and EVEN... USB A Male to open end wire. I can't even believe it... :biggrin:

I'll be ordering up some fans, usb cables, shrink tubing and whatever else I can find in their catalog soon!

Thanks for all the help!
 

Similar threads

Replies
12
Views
1K
Replies
2
Views
1K
  • Electrical Engineering
2
Replies
41
Views
3K
  • Electrical Engineering
Replies
14
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
488
  • Electrical Engineering
Replies
21
Views
5K
  • Electrical Engineering
Replies
6
Views
6K
Replies
6
Views
1K
Replies
6
Views
3K
  • Electrical Engineering
Replies
20
Views
2K
Back
Top