Fan Noise

[raptor1956]

So I built an LED work light using three 750mm strips of LED lights and purchased a nice aluminum box (100mm x 100mm x 50mm) to put the buck converter and controls in and even though testing showed the PS didn't get much more than warm at the highest setting I decided to put a small 40mm fan inside to provide a small flow of air just in case.  I powered everything up and that little fan, which was dead quiet by itself, but when mounted inside the box made an annoying whine. 

The Al box is made in four parts: the bottom, a top that slides on, and the front and back covers.  I mounted the fan to the back cover and the switch, pot, and LED voltage display to the front cover.  So, today I took it apart and removed the screws mounting the fan to the back cover.  I then attached four small strips of foam cored double sided tape about 3mm x 8mm at the location of the fans corners and stuck the fan to it.  I then sealed around the edge with some silicone sealant both to seal the fan against the cover and maybe to offer some vibration damping effect.  For good measure I threw a could diodes in series with the fan power to cut the speed a bit.

I am very pleased with the result -- it's not dead quiet, but it is barely noticeable and I'm a happy camper at this point.  The thing with these fans is that they are often real quiet when sitting there by themselves, but the moment you mount them to something the thing you mount them to becomes a sounding board greatly amplifying the sound. 

First world problems -- I know...


Brian

[Zero999]

I'm glad you managed to quieten the fan but why did you fit one in the first place if it doesn't get too hot?

[kmossman]

Use a gasket or such - not just sealant around the edges

Screw in well.

Your fan may have needed a 'better' power supply - use a diode [in series] and large capacitor [in parallel after the diode]

Often using a lower voltage will reduce noise

[raptor1956]

I'm glad you managed to quieten the fan but why did you fit one in the first place if it doesn't get too hot?

Just being anal I guess.  I should mention that the testing I did was NOT inside a closed box so without a way to vent the only way for heat to escape is to heat the air then heat the box (Al) then have the heated box shed heat through radiation, convection or conduction.  So, I probably didn't need it but I added it just in case.


Brian

[raptor1956]

Use a gasket or such - not just sealant around the edges

Screw in well.

Your fan may have needed a 'better' power supply - use a diode [in series] and large capacitor [in parallel after the diode]

Often using a lower voltage will reduce noise

The fan, when powered from the same buck converter that powers it now was quiet as a mouse when outside the box but annoying when mounted to the cover.  The way I have attached now isolates it from direct mechanical connection with the sound board like rear cover and the combination of foam cored double sided tape and silicone makes a good seal while damping the sound generation.  I'd guess the mounting method probably reduced the sound level by about 15db and the diodes in the power probably cut a few more db.


Brian

[nctnico]

Rubber fan mounts do wonders to stop vibrations from a fan being transferred into a case.