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[MadMax]

hi
    may be the wrong place to post .but i will have a go
    i need to know how to slow a 12volt computer fan down....it is not been used in a computer
    it is been used in a smoke /mist macker and is very fast for what i need
    can anybody help me
                                                   regards
                                          madmax

[essex2visuvesi]

Reduce the voltage. My dad uses these too cool his marine aquarium, using a variable voltage power supply he can control the fan speed.
A simple brushed esc would also do the job, or a variable resistor as the current draw is quite low

[nivapilot]

I would go the esc route, some very small ones are available, I have two for experimenting with.
That way you can vary the amount of "smoke" produced.....even making it look like the boat engine is working harder.
or variable pot, and set it to the amount you want before setting off.

http://www.ebay.co.uk/itm/New-10A-Brushed-ESC-Motor-Speed-Controller-for-RC-Car-Boat-Tank-Without-Brake-/322082820053?hash=item4afda1cfd5:g:aWEAAOSw2GlXGIcU

[essex2visuvesi]

I would go the esc route, some very small ones are available, I have two for experimenting with.
That way you can vary the amount of "smoke" produced.....even making it look like the boat engine is working harder.
or variable pot, and set it to the amount you want before setting off.

http://www.ebay.co.uk/itm/New-10A-Brushed-ESC-Motor-Speed-Controller-for-RC-Car-Boat-Tank-Without-Brake-/322082820053?hash=item4afda1cfd5:g:aWEAAOSw2GlXGIcU

If you want one of those, let me know..... I've got a load of those in the parts box

[Hellboy Paul]

Restrict the air flow using a piece of plastic card over the fan

[MadMax]

thank you for replys on this post
i think i will go down the variable resister road
for give my lack of knowledge on this subject but do i break the live feed with this resister or can some please
tell me how to fit it
                                                           regards
                                                    madmax

[The Old Fart]

I use these to control the fan speed in the smoke units I make.

Code: [Select]

LM2596 Voltage Reducer board - 3.5V to 30V in, 1.2V to 30V out
Bit pricey on Ebay, but never had one fail.

lot cheaper here.

Code: [Select]

http://www.aliexpress.com/item/Ultra-small-LM2596-power-supply-module-DC-DC-BUCK-3A-adjustable-buck-module-regulator-ultra-LM2596S/1620458430.html?tracelog=rowan&utalgorithmid=2&utcontentid=976&ck=in_edm_other&rowan_id1=eclc_en_7_1_en_US_2016-05-11&uttaskid=37002&rowan_msg_id=theoUTT_37002_%24095295b0d18142f7834e5e0dee7d7158
this is where I get mine from.

[essex2visuvesi]

Also on evil bay
http://www.ebay.co.uk/itm/LM2596-Voltage-Reducer-board-3-5V-to-30V-in-1-2V-to-30V-out-UK-STOCK-/231690512467

[malcolmfrary]

The resistor option is electroncally the simplest and easiest to fit.  Cut a wire, join the two ends with the resistor.  The difficult bit is working out the right value and rating.  This is in the area of "If you need to ask, you should first ask if you should be at this point".
The most certain to work is a cheap ESC that is rated for the voltage intended.  The one suggested earlier will form its own smoke unit on 12 volts.  Running it on the max 8.4 volts (2S LiPo, fully charged) that its instructions advise will slow the fan down anyway.
How big is this fan?  Apart from restricting the airflow, a smaller one would probably do the job.

[Geoff]

In my experience the best way is to get a smaller fan or to use a blanking plate to restrict the airflow. I tried using a variable resistor on one and it worked well until the battery voltage began to drop due to usage and the fan would then not start at all. They need 12 volts to start reliably but will run on a lesser voltage and therein lies the problem. The result was the heater element worked fine but the fan didn't start so the whole thing overheated and caught fire (assuming you are using a glycol/hot wire type). If nebuliser type no chance of a fire.

[malcolmfrary]

http://www.electronics-tutorials.ws/blog/pulse-width-modulation.html - some notes on DC motor speed control, plus, about 1/3 down the page, a nice drawing of the circuit for a PWM control to run on 12 volts.  Since its pulsed, there is never any problem about starting as with varying voltages and guessing the right resistance.

[MadMax]

thank every body that replyed to my post ....all very interesting ...but igot a little gismo from china
that rurned the voltage up and down ...just what i wanted
                                                                    so thank to all