Adding resistor to fan?

[SMOKEU]

I've got a fan that plugs into an AC wall socket, but then it has what I think is a AC/DC converter, check the pic out below. Is there any way I can add a variable resistor somewhere so I can adjust the fan speed? Preferably without getting shocked or setting fire to anything.

http://i305.photobucket.com/albums/nn204/SR20NP/Computer%20stuff/ups.jpg

[Hitcher]

I find that tear gas works really well at keeping my fans at bay.

[neels]

Chop off the output lead from the plug pack (the one that doesn't have the 3 pin plug on it),get yourself a wire wound potentiometer and join it in series with one of the leads, it's all they used to do for variable speed heater fans in cars back in the 60's and 70's.

[Oakie]

I find that tear gas works really well at keeping my fans at bay.

Didn't know tear gas came in single serve doses. :)

[bogan]

Should be doable to put one in on the low voltage side. 5V at 1Amp is 5W, but you might find the PSU is overated for it, better to get the specs from the fan. If its a BLDC fan you'll have an operating voltage range which cuts off at some volts, so you'll want to put a resistor in series with the variable resistor so you don't waste most of the adjustment range, and to take a bit of load off the resistor.

[pete376403]

a pic square on to the label would make it easier but it looks like 9 (or 5) volt, DC, positive centre contact, so yes, you should be able to add a variable resistor (potentiometer) into the circuit

[SMOKEU]

If it's any help it looks like a 120mm computer fan, except for the fact that it's much thicker. Looks like something that you'd find in a server.

[FJRider]

I find that tear gas works really well at keeping my fans at bay.

Still on the drugs ... huh .. ???

[bogan]

If it's any help it looks like a 120mm computer fan, except for the fact that it's much thicker. Looks like something that you'd find in a server.

Just chuck some resistors in there and see. 5V 1A, good place to start is probably a 5ohm 5W potentiometer. Thinking about it more, you only want a potentiometer, and not a fixed resitor. 5 ohm should reduce the voltage to just below half. A PC type fan won't be grounded so it doesn't matter which wire you put the potentiometer on.

[SMOKEU]

Just chuck some resistors in there and see. 5V 1A, good place to start is probably a 5ohm 5W potentiometer. Thinking about it more, you only want a potentiometer, and not a fixed resitor. 5 ohm should reduce the voltage to just below half. A PC type fan won't be grounded so it doesn't matter which wire you put the potentiometer on.

Sweet, there are only 2 wires going into the fan.

[Berries]

I reckon you are going to need five chimps for that.

[Virago]

I'm sure Akzle will be along soon to impart his superior electrical knowledge...

[Swoop]

Didn't know tear gas came in single serve doses. :)
There are test capsules (much like a pill) that would suffice.
http://www.defense-technology.com/pdfs/specs/1693_CS%20Capsules%20Rev%203-12.pdf

[FROSTY]

I find that tear gas works really well at keeping my fans at bay.
restraining orders work better --just sayin

[Coldrider]

You can use resistors, even diodes will cause a voltage drop. I'd go for pulse width modulation myself, same as how i get variable heat output from fixed output hotgrips.

[SMOKEU]

I sorted it a different way in the end. I removed the existing fan and added on a standard 120mm computer fan. I then cut a hole in the side of my ATX case to put a wire through to connect up to the computer fan controller. It works nicely as the computer is right next to the UPS (which is what the fan is for).