Author Topic: Matching Battery to PC fan load  (Read 2088 times)

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Offline regalzack

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Matching Battery to PC fan load
« on: March 05, 2014, 05:17:10 am »
Alright so long story short I want to power a cpu fan with a rechargeable Usb Pack. I'm not even sure if this is possible as I'm not sure whether or not USB rechargeable batteries are voltage regulated... Here is the battery I'm considering (http://www.amazon.com/Intocircuit-Ultra-Slim-Lightning-Sensation-Thunderbolt/dp/B00EH3I13Y)

Battery: Output #1: 5V @ 1A
        OR Output#2 5V @2A

Fan draw: typical draw 12V @ .15A

So, I'd like to know if this is possible and if so, I would like the steps to figure out how to make this work.

Thank you so much!
 

Online Psi

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Re: Matching Battery to PC fan load
« Reply #1 on: March 05, 2014, 05:20:26 am »
Yes, you can connect a 12V CPU fan to a 5V USB recharge pack and it will spin around and move some air.

However, the fan will run noticeably slower because it's receiving 5V instead of 12V.
(This is actually a common technique for reducing the noise from computer case fans. People often swap the molex pins around to run them from 5V instead of 12V)

Are you going to use the CPU fan for some other purpose? I ask because an actual CPU may get a bit hot with the reduced cooling from 5V.
You should try it on 5V first and see what sort of cooling/airflow you get and decide if that's enough.

Steps are as follows.

1) Cut an old USB cable up so you have a normal USB connector and a nice length of wire coming out of it
2) Strip the insulation back to get at the wires
3) Solder the red wire in the USB cable to the red wire of the fan
4) Solder the black wire in the USB cable to the black wire of the fan.
5) Put some tape/glue/insulation around your solder joins and around the un-usued USB wires.
6) Plug the USB cable into the recharging pack
7) Hit the button on the charging pack and the fan should spin

99% of USB charging packs output 5V as soon as you hit the button on them. However a few weird ones require resistors/shorts on some USB pins to 'inform' the charger that there's a phone connected
« Last Edit: March 05, 2014, 05:36:27 am by Psi »
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Offline calexanian

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Re: Matching Battery to PC fan load
« Reply #2 on: March 05, 2014, 05:37:34 am »
If you want to get fancy you could even build yourself a boost converter. Look up a MC34063. Its a 1.5 amp boost converter that is easy to use and available in 8 pin dip at a low cost. Would have no problem boosting 5 to 12.
Charles Alexanian
Alex-Tronix Control Systems
 

Offline regalzack

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Re: Matching Battery to PC fan load
« Reply #3 on: March 05, 2014, 05:41:20 am »
I'm actually going to build a solder defumer into an old cigar case-- so it may be fine, Im not sure what sort of cfm I need to suck through a carbon filter, but I'd be willing to bet 5v would be adequate. I just, well prefer efficiency. I am open to suggestions.

Thanks again.
 

Online Psi

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Re: Matching Battery to PC fan load
« Reply #4 on: March 05, 2014, 05:51:18 am »
Even the solder fume extractors you can buy don't work if you're more than say 15cm of the front when soldering.

They're usually 130mm 20-30W fans and run from 240V directly (and quite noisy).
Most people turn them around 180deg on the desk and use them to blow instead. This seems to works better to stop fumes getting in your face but obviously doesn't remove them from the room as the fumes dont get pulled into the filter.

I really cant see a little CPU fan working for solder fume removal. Maybe a delta cpu fan would have a chance.
« Last Edit: March 05, 2014, 05:52:57 am by Psi »
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Offline calexanian

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Re: Matching Battery to PC fan load
« Reply #5 on: March 05, 2014, 06:43:03 am »
From a operator perspective, blowing the smoke away is more effective than sucking it up. If this is for occasional soldering just point the fan across the desk and open a window. I was born into a pcb assembly family and have had my same job since I was young breathing RA flux smoke all my life. Haven't died yet! Just get some air flowing across.
Charles Alexanian
Alex-Tronix Control Systems
 

Offline G7PSK

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Re: Matching Battery to PC fan load
« Reply #6 on: March 05, 2014, 09:08:35 am »
You can get computer fans in both 12 volt and 5 volt look on ebay lots there.
 

Offline rexxar

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Re: Matching Battery to PC fan load
« Reply #7 on: March 05, 2014, 02:22:25 pm »
I use a PC fan to suck solder fumes away. It will usually suck solder fumes from 3-4 inches away, but I usually run it at 9V or so, just to keep it quiet. I can turn it up to 12V or more, and get a more respectable working distance, but it's loud as hell. For whatever reason, it never occurred to me to use the fan to blow the fumes away, that would probably make more sense  :palm:
 


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