Circuits with fans, should be pretty easy.

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What's actually going on

I don't think I ever posted what this was actually for. CAD renderings posted below. Copper heatsink with a rubber shell. Fans are inside pushing air through the grooves.
 

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Kirro said:
3) The fan and motor combination must have an extremely low profile (<3/4in), low power consumption, and low to medium amount of air movement.
You just kind of shot yourself in the foot with that one. If low-medium is all that you need, then running your 12VCD fan motor at 3-6VDC is all that you need. The USB port, therefore, is adequate.
 
When I put 5v (USB) through a 12v fan it won't even spin. I also tried 6v (4x AA), that also did nothing.

I know this because I tried.
 
Hmm... that's unusual. I routinely run DC motors at reduced voltage with no problems. Yours must have a really high starting resistance.
Now that your CAD pictures are visible, I have to ask if you're sure that the design will work as you want it to. It looks to me as if it would just create a static region in the centre.
 
Kirro said:
If I only have 5v, how would you propose to generate extra voltage to bump it up to 12v? I say 12v because that's what all the fan/motor combinations that I can find require.

DC-DC Converters that I have found are super expensive and too bulky to be portable. The required budget for this project is minimal, around $30-$40 USD.
http://www.national.com/an/AN/AN-1066.pdf#page=1

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.
 
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National Semiconductor also has a (relatively) powerful online power supply tool called WEBENCH:

http://webench.national.com/appinfo/power/webench/index.cgi

- Warren
 
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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 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.
 
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berkeman said:
http://www.national.com/an/AN/AN-1066.pdf#page=1

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]
 
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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
 
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.
 
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
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.
 
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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.
 
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!
 
Every site I've found that carry these fans have minimum orders of 200+ or handling fees of $15 + shipping.
 
Kirro said:
Every site I've found that carry these fans have minimum orders of 200+ or handling fees of $15 + shipping.
?? 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:
 
... 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!
 

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