Hello

I've come from a background where I constantly played with the electronics in my toys, scalextrics and any little motors I could get my hands on.

After many years of dormant activity, I've decided I'm going to go back to it, albeit with more exploration and practicality.

I'm looking for a variable/adjustable power supply that can output perhaps 30v (nothing to a level that I could hurt myself with). I'm hoping to build a custom air duct for my window. I will probably use a cheap PC case fan in-conjunction with the variable power supply to give control over the power so that I can decrease the voltage if it's too loud.

I may look into larger fans but for now I'll go with the cheaper option, just in case it all goes down the pan and the idea turns out to be useless.

Any help would be appreciated.


Thank you.


p.s. I'm from the UK and the site CPC | CPC - Over 100, 000 products from one of the worlds leading distributors of electronic and related products. has a lot of useful products which may be useful if you find a product I should buy.

 

I wouldn't recommend using a variable voltage supply just to control the speed of a fan. I'd recommend a PWM (Pulse Width Modulation) controller.

What's the maximum voltage rating of the fan you want to use? 30V sounds like the absolute maximum rating for a 24V fan.

Do you want this to be mains or battery powered?

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Make sure of the control method. Some PC fans are controlled by the driving frequency, so neither vairable voltage nor PWM will work.

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I'm quite new to this subject area despite playing with it as a kid so you'll have to bear with me as I research into the things you guys mention.

I want this to be as easy and as quick as possible so if there's an off-the-shelf PWM with integrated power supply (or can easily be connected to a 12v DC power supply) then that would be welcome.

Ideally, I won't have to do any soldering or very little if possible - that way I can just pop the connectors together (bit of a bodging) and bingo, I got my set-up ready to then build a tube to go from my window into my room.

Hero999
- The volts for a PC case fan comes at typically 12v, however I'd like to be able to go past it's standard voltage recommendation as I'm a bit crazy like that and enjoy pushing things past their limits. Either way, I might find myself being able to move more air quicker by increasing the amp/wattage by a little amount that's over the recommended level to a useful degree (and thus saving money on buying a more expensive fan).
- It will be mains powered.

BrownOut
- Perhaps I should use a different fan altogether. I don't care if I happen to buy a PC case fan and it doesn't work, they are only 99p


Thanks a lot for your replies, I'm really excited about this!

 

I don't know anything about your fan. I"m only suggesting a little research on it's operation before putting in the effort of building something that will only result in frustration.

Good luck!

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A cheap fan should be easy to control with PWM.

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I have been told these parts will work together:

inline potentiometer
Dual 10K Potentiometer, 6 Inline Pins, Linear taper on eBay (end time 11-Jul-09 04:30:31 BST)

12v dc psu
12v 1 Amp AC DC Power Supply / Adaptor CCTV Etc on eBay (end time 01-Aug-09 15:46:41 BST)

pc case fan
New 80mm PC Computer Chassis Case Cooling Fan Quiet 8cm on eBay (end time 05-Jul-09 15:28:48 BST)

 

A potentiometer will always need your attention because at low speeds, when temperature changes it may stall/change rpm. It is ineffective and inefficient.

Use rather a PWM fan controller. Check out this PWM fan controller circuit.

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This does look useful, however is there a pre-made one I can buy? I don't have time to make one of these circuits.

Thanks.

 

MX066 - DC PWM Motor Speed Controller - Assembled & Tested

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Thanks for the link. Is there any reason why it's so expensive?

Oh and, would I be able to almost blow up a PC case fan (by going very fast) with this if I was so inclined?

I'm interested in buying a bigger and more powerful fan if my objective cannot be achieved and I'm wondering whether the component you linked would be capable of something like this.

Thanks again.

 

30$ is not expensive. It controls 30 Amps. There are also ready made from thermaltake or other companies for PC coolers, with fancy pots and LCDs, designed to fit in single or double 5.25 cases. They start from 35 and go higher,

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Because it's designed for 30A, your fan probably only uses 300mA (1/100th of the current) so it's really overkill but will work. Most motor controllers will be designed for large motors, there isn't much demand for small motor controllers.

Only if you do something stupid like connect a 12V fan to a 24V supply.

With a 24V supply the controller can power a 720W fan, nearly 1HP and with a 12V supply it can power a 360W fan. A 720W fan will probably blow your computer to pieces.

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I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

I'm interested in buying a fan or multiple fans depending on how much air I can push. This is so I can make my own custom air duct leading from my window into my room. I'll install a filter for flies/nats and take it from there.

I'm heavily considering buying this product now due the ability to rank up the volts if needed. Perhaps I could even power a whole house fan, or one of those smaller fans which I've forgot the name of that are used in kitchens.

 

Why blow around hot air with a fan?
Get an air conditioner instead.

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