Help with custom fan please.

[ShadyK]

Hi every one. Thank you all for the help from my last few posts.

 I am in the start up of creating a little desk fan for usage when i do little soldering jobs i no its not ideal but it gives me the practise i need thats all. And i can use it too. So here it goes. I plan to run it off battery as its not too advaced so would i just buy 2 fans (pc fans) with a 9v batery housing a switch and then som wire and connect them all together? Sorry im not arragant so if this ide seems its im just really new to it thats all thanks guys..

[SeanB]

It will work, but will eat batteries pretty fast. Do you not have an old wall wart or cellphone charger that you can use to get 5-12V to run the fans with? just cut the end off and strip a little of the outer back to get the red and black wires inside and connect the fans to them.

[senso]

I use a 120mm fan recycled from an Atx supply, at 5v, it just makes a nice breeze that takes all the fumes out of the way.

[ShadyK]

Yeah i have a charger and does it mater what side the red and black go to aslong as the black are with balck and red with red?  Also could a switch and LEDS be intergrated into it? I dont know what it is but at the minute im obsessed with putting leds in every thing. Thank you for ur quick reply.

[Six_Shooter]

It's normal to want to put LEDs in everything, I think we all go through that phase, or never get through it. LOL

Usually, the LEDs in everything grows to seven segment displays in everything and then onto LCD displays...

Anyway...

The best thing to do when trying to re-purpose an existing power supply, or wall wart in this case, and are not sure of the polarity, is to use a DMM to find the polarity of the voltage to be sure that you're connecting the polarity correctly.

You could set this up a couple of ways, one way would be, as suggested, cut the end off the wire(s) of the wall wart, and connect directly to your project.

Personally I prefer to leave the wall wart unmodified for a couple of reasons I will get into later. You can pick up the female end that matches your wall wart, to be able to make a nice little circuit, in an enclosure and plug the wall wart into it nice and clean. This serves a couple purposes, if you ever need to replace the wall wart, you should be able to find the same one or similar that will have the same connection. Also if for some reason you have the wiring hanging in such a way that it gets caught on someone or something as the walk past your work area (among other possibilities) it is more likely that the wire will become unplugged from your fan set-up, than pull it and a lot of other stuff off your work area. Apple actually used this idea in a magnetic power plug for this very reason, someone else used it too, previously, but Apple had better marketing, so...

If you integrated an adjustable voltage regulator into the circuit you could control the fan speed, there are other ways as well, but are more advanced topics.

[ShadyK]

thnks for ur reply..

I thought i was going to snip the end of my old nokia charger off then join them to a switch then join the fans that?. your idea Six_shooter sounds a lot better with adjustable speeds and stuff?. could u elborate abit more please?. And LEDS yeah for some reason i want to put them into every thing lol. cheers.

[Shock]

Red should be positive on the fan if it's a 2 wire PC variety it will also show it's rated current draw and voltage on the fan.
Of course to run it full speed the power supply will need to have the same voltage and supply a higher current than the device.
The diagram on the power supply will tell you if it's center positive or negative.  You also can use a multimeter to verify this.

You can test the fan first if you like with a 9v battery.  If you don't have hookup connector or wire some twist ties with stripped ends will work.

If you have a soldering iron buy a suitable surface mount socket and you can leave the connector on the power supply and swap it between projects.  Prototyping PCBs can be delivered to your door on ebay for as little as a buck.

For theory on running LEDs you should watch something like the video below and calculate it based on the LEDs your intending to use.