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Turning off noisy fans in Led cans


nathan61

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Forgive my question- this is probably a terrible idea, but I am in a desperate situation. I am producing a high school play at an outdoor theatre in Antananarivo, Madagascar. I have a mix of lights, and to do a halfway decent job on the lighting I will need to use everything we have.

 

Unfortunately half our lights are noisy par64 LED lights made by some Chinese manufacturer called Jinshan. They work fine, but the fan noise is unbearable. I am thinking of entirely disconnecting the fans, or at least putting a capacitor on the fan so it runs slower. I don't need to run these lights for all that long. Does anyone have some idea as to what would happen if I disconnected the fans? If the lights lose some life or efficiency then I can live with that. But.....if they explode or melt then that would put a damper on the show!

 

I know this is not an ideal situation, but out here in Madagascar I don't have access to much equipment, so I have to improvise. Many thanks for any replies.

 

 

 

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Fans in any piece of kit are pretty much there for one reason - to keep the guts of whatever it is cool during normal operation. So whilst these LEDs may not 'explode' if you cut the fans, they most certainly will overheat.

 

Now, given that your event is in the open air that MAY give your fans less work to do, but not knowing the climate of Madagascar (though I suspect it's considerably warmer than the UK average temp) it MAY in fact give them more to do...

 

The question has to be WHY are the fans making so much noise?

My guess would be that they're either dirty or they have worn bearings or possibly both.

First suggestion would be to get the fans cleaned out. This could be as easy as using a vacuum with a long bristled brush although if it's caked on the fan blades that won't work too well. If that's the case, or if the bearings are shot you're looking at replacements, as I'm betting the fans will be enclosed and hard to get at for any serious cleaning.

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Thanks you for the quick reply Ynot. As you suspect it may be a little warmer here than the UK, but nothing drastic since we are at higher elevation. The noisy lights are fresh out of the box and hardly used, and the first time we hooked them up they were noisy. The fans are clean, but they are quite high powered, and probably cheaply made, so I suspect that is why they make such a racket. The acoustics of the stage also amplify the sound.

 

I've read that LED lights generate a lot less heat than other bulbs, but they lose a lot of efficiency etc when heated up. This is what has led me to believe that I may get away with operating them without a fan. I am willing to lose some efficiency to gain some peace and quiet, but before I go ahead and test this out on just one light I just want to see what people on this forum can tell me.

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I am thinking of entirely disconnecting the fans...

The biggest killer of LEDs is heat. If you really want to do this I'd do an experiment and do one unit and run it to see how long it lasts. It might work; it might fail. If it works it will almost certainly shorten the remaining life of the units.

 

...or at least putting a capacitor on the fan so it runs slower.

Unlikely to work as the fans are usually DC.

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As mentioned by the others, the fans are probably required to dissipate the heat from the LEDs which generally need cooled. If the fans are a standard size and 12V then you could change them for the quiet computer fans previously mentioned. There are some with feathered blades to reduce noise. To reduce the speed of the fans you could use a resistor in series, but this will reduce the cooling capacity. That said, it doesn't take much speed reduction to reduce the amount of noise dramatically. If the fan is a 12V type then putting 3 or 4 standard 1A diodes in series with it will drop the voltage by about 2V and reduce the noise considerably.
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On the ones I'm familiar with, the fans are DC, running off the 24V rail from the PSU.

 

They are noisy, so I have considered making them variable speed with a temperature sensor on the heatsink, but "considering" is as far as I've got.

 

http://davidbuckley.name/pix/led_inside.jpg

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Forgive my question- this is probably a terrible idea, but I am in a desperate situation. I am producing a high school play at an outdoor theatre in Antananarivo, Madagascar. I have a mix of lights, and to do a halfway decent job on the lighting I will need to use everything we have.

 

Unfortunately half our lights are noisy par64 LED lights made by some Chinese manufacturer called Jinshan. They work fine, but the fan noise is unbearable. I am thinking of entirely disconnecting the fans, or at least putting a capacitor on the fan so it runs slower. I don't need to run these lights for all that long. Does anyone have some idea as to what would happen if I disconnected the fans? If the lights lose some life or efficiency then I can live with that. But.....if they explode or melt then that would put a damper on the show!

 

I know this is not an ideal situation, but out here in Madagascar I don't have access to much equipment, so I have to improvise. Many thanks for any replies.

 

 

 

 

 

There are different types of fans available, There are high output fans (hi speed) fans, these are the noisest !

 

If you replace these types of fans with the quieter type fans, you will find the quieter fans move less air,

 

so over heating issues could arise !

 

If you use them in a cool eviroment and not for long periods, you might get away with it !

 

But its a gamble at best !

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I wonder if your fans would operate satisfactorily if you wired them in series.

 

Probably not. These fans have brushless motors and thus have integrated the electronics to drive said brushlessness, and generally sticking electronical stuff in series results in unequal sharing and thus one fan undervoltaged and the other overvoltaged, possibly to an unacceptable degree. And if that subsequently kill a fan fails then both'll stop and suddenly weve got no coling at all...

 

Solving 24V to 12V would be easier, one of those little switcher PCBs from China for $5.

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thanks for all the ideas. The lights I have are similar top the ones in the photo posted by dbuckley. I am going to open it up today and see if I can figure out what type of fan is in there. Unfortunately the fan is quite large, so I suspect it is 24volt. I did figure out that the back of the can was rattling against the front a little, so dampening this with some electrical tape actually helps quiet it quite a bit.
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Hiya,

 

Can you post a picture when you open up the inside of the unit? Just thinking as I had a similar problem with some Chinese ones that came in cause they were rattling, and it turned out the fans were missing two of the screws on one side, so the fan was vibrating against the heatsink when it got going.

 

Just a thought :)

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My buddy just opened it up and we had a look.... surprisingly the fan is 24 volt Sanyo (Japanese!). It is screwed in well, but it is a big enough fan running at high enough RPM to make a lot of noise. There is no heat sink behind the LED panel, like on the picture posted by dbuckley. We ran the light for a while, and very little heat was produced by the LED, but I didn't have it hooked up to a board, so I am not sure if it was on full strength.

 

Is the fan mainly there to cool the lights, or the power supply? Next we will try putting in a potentiometer or rheostat so I can turn down the fan or turn it off. I am not sure if I will have much room to actually turn down the fan before it stops turning entirely, but I like the idea of being able to turn the fan completely off. In many cases I will only want to use the LED lights for a few minutes at a time, and I doubt they would overheat in this short period of time. I'll post the results of this little experiment soon!

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