Computer Port Voltages and Computer Fan

[dimoes]

Hey, i need help with a small project. I don't know where else to post this question, but it has to do with voltages and ports, so i guess here might be a good place.

I am trying to suck hot air from the top of my room to the outside using a long circular air duct(i think its from a my old dryer). At the bottom of the duct i have connected an 80mm computer fan which is powered by a single usb port.

I am under the impression that a usb port outputs 5v, and i need at least 10v to power my fan at semi-full capacity. My idea was to wire one usb to another and then connect both to the fan combining the voltage. I don't want to blow up my computer, but in theory(which is probably wrong...) it should work cause it would be like connecting 2 batteries positive to negative, and then using both to power whatever...

Anyways, I have no idea if my idea will work and am wondering if anyone can help me out.

I would also consider using another port if possible. I would prefer not to go into the case and use the power supply directly as I am using a laptop for this project.

Thanks in advance for any assistance

 

[doolittle]

Sorry if you were looking for a geek solution over a bob vila solution, but just to give you more options - have you thought of not using the computer at all for the project?

If you live near a home depot check these out (depending on the size of the duct):

Inductor - 8 In. In-Line Duct Booster Fan ~$30
Model DB208
Internet # 161327
Catalog # 100080191
Store In-Stock SKU # 295273


Inductor - 6 in. In-Line Duct Booster Fan ~$25
Model DB206
Internet # 161326
Catalog # 100067594
Store In-Stock SKU # 295261


Inductor - 4 In. In-line Duct Fan ~$22
Model DB204
Internet # 164173
Catalog # 100073963
Store In-Stock SKU # 113946


A few sheet metal screws & duct tape (maybe an extension cord) and you are all set, or plug it into a dimmer switch to adjust the flow, or get one of these:

Ductstat - Plug-In Line Voltage Thermostat ~$28
Model DS100
Internet # 161328
Catalog # 100028788
Store In-Stock SKU # 197598



This can help bring cool air in the room:

ENTREEAIR - Door Frame Fan ~$20
Model RR100
Internet # 164174
Catalog # 100080304
Store In-Stock SKU # 164333

 

[jap0nes]

I am under the impression that a usb port outputs 5v

yes

My idea was to wire one usb to another and then connect both to the fan combining the voltage

you'll be lucky if your computer detects the short circuit and just shut off, but you may end with a burned usb port, maybe your motherboard.

 

[dimoes]

Nice idea with the duct fans. I'm thinking of getting the 4inch fan that blows 80 cfm = 2.24meter^3/min(1cfm = 0.028m^3/min). Since my room is 58m^3, it would take approx. 30 mins for it to fill/empty my room of air.

Similar to case cooling decisions, i need to decide what to do with my 2 fans. I don't know what would be more efficient, to blow in 80cfm of cool air every 30 mins and blow out 12cfm = 0.3m^3/min(computer fan running at 5v), or the other way around.

The above setup makes more sense, since i only need to get rid hot air collecting at the top of the room, effectively reducing the volume of air i need to move out to possibly 12m^3.(top 1/2 m from ceiling). That would take 40mins if my calculations are correct.

The problem is, my house is decently cooled when the ac is on, however, being on the 2nd floor, and in the hottest room, i have no idea whether I'm simply not recieving my share of the ac, if im getting all the hot air from the house, or if i'm loosing alot of ac to cracks/windows/whatever...

I'm gonna assume that its probably a combination of all of these, which would explain why my room is at least 5 degrees above my house temperature all the time.

Any ideas in regards to increasing computer fan voltage using computer ports???...it wouldn't feel right running 2, 30 watt fans at once. Since I use my laptop most of the time i'm in my room, it would save energy.

I can see how i would make a short circut with the 2 usb port idea, but any solution??

 

[jap0nes]

a window can be influencing, maybe direct sunlight hitting your walls too. Try to close your curtains when the a/c is on.

I don't know what would be more efficient, to blow in 80cfm of cool air every 30 mins and blow out 12cfm = 0.3m^3/min(computer fan running at 5v), or the other way around.

you can use the same principle of computer cases:
- put one blowing cold ar in, at the bottom, preferably sucking air from where there's no direct sunlight
- put another one blowing hot air out, near the roof.

 

[cat900s2]

Hey back to the original subject, can we get 10v of power being pushed down the usb cable to the perpherial?

 

[jsc]

No. You will short out the motherboard. If you do want to use the computer, simply run one of the molex drive connectors outside the case and plug the fan into the yellow and black wires.