rdodger
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| posted on 14/12/13 at 03:36 PM |
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Run a PC fan from mains
I want to run a PC fan from 240v through a transformer.
I tried one this afternoon using a digital 12v dimmable lighting transformer with little success. Basically the fan turned slowly then went bang and
stopped!
Any one point me in the right direction?
PS. A PC power supply would be a too large to fit where I need it.
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Slimy38
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| posted on 14/12/13 at 04:01 PM |
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Laptop power supply? Most of those put out 12 volts, and a great deal smaller than the average PC power supply.
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40inches
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| posted on 14/12/13 at 04:04 PM |
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Is there any reason you can't use a 240volt fan of the same size?
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rdodger
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| posted on 14/12/13 at 04:21 PM |
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Thanks for the replies.
It's all about the noise.
We have bought this electric fire with flame effect. The flame effect is achieved by illuminated ribbons blown by a fan.
The fan is really noisy. I want to replace it with something as quiet as possible. At the moment I can't here Kit Car Crisis over the noise of
the fire!
I thought that 12v axial fans would be quieter than 240v ones?
The heat comes from a fan heater which is also noisy but swmbo says we will never have the heat on.
No I don't know why we bought it either!
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gremlin1234
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| posted on 14/12/13 at 04:28 PM |
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it will be a dc fan, put a diode in series.
or use a 5v fan and tiny (usb or phone) psu
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rdodger
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| posted on 14/12/13 at 04:36 PM |
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quote:
Originally posted by gremlin1234
it will be a dc fan, put a diode in series.
or use a 5v fan and tiny (usb or phone) psu
Aha of course! How stupid am I?
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rdodger
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| posted on 14/12/13 at 04:38 PM |
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Could I use one of these?
http://www.ebay.co.uk/itm/220-240V-to-12W-DC-12V-LED-Driver-Power-Supply-Transformer-For-MR16-MR11-Lights-/221299285867?pt=UK_Home_Garden_Wall_Lights&
amp;hash=item3386771f6b
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MikeRJ
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| posted on 14/12/13 at 05:31 PM |
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You can buy quiet 240v AC axial fans, and you can get ridiculously loud 12v fans. What size do you need?
[Edited on 14/12/13 by MikeRJ]
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rdodger
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| posted on 14/12/13 at 05:37 PM |
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80mm would do it.
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Barlidge
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| posted on 14/12/13 at 06:08 PM |
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I used to run a couple of 12v 120mm fans over the top of a fish tank with a variable transformer similar to the one below, the benefit is by dropping
the voltage it slowed the fans down making them pretty much silent and giving just a gentle breeze.
http://www.ebay.co.uk/itm/Universal-Mains-Plug-Power-Supply-AC-DC-Charger-Adapter-Adaptor-600mA-3v-12v-/400572748001?pt=UK_Sound_Vision_Other&hash
=item5d43ff10e1
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MikeRJ
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| posted on 14/12/13 at 06:34 PM |
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For a given airflow, the slower the fan speed the quieter they tend to be. This means decent airflow and low noise favours as large a diameter fan as
possible or in other words a 120mm fan of the same airflow rating will be significantly quieter than an 80mm one. If you can use a bigger fan then do
so.
Mains fans in the standard axial sizes tend to be made for industrial equipment, and have high quality metal frames and impellers which is reflected
in the price. Cheap 12v fans are available due to the extensive use in PCs, but they are plastic, often poorly made and can have limited life
(especially if it's going to get hot around the fan).
Something like this
PAPST fan (PAPST make top quality fans) or the higher airflow and slightly noisier
Bisonic fan might do the trick.
For the lowest possible noise a
quite PC fan and a 12v power supply is likely to be somewhat cheaper than a proper equipment fan, but these super quiet fans
have a very modest airflow that may not be sufficient for you purpose.
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BenB
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| posted on 14/12/13 at 06:54 PM |
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80mm 240v ac fans are about a tenner from maplins or ebay import from hk for about seven quid. I've just fitted a couple to my temp controlled
fermentation chamber. It may even be possible to run them via a dimmer switch for volume control.
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rdodger
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| posted on 14/12/13 at 06:57 PM |
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OK thanks guys. I will get myself to Maplin
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gremlin1234
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| posted on 14/12/13 at 07:48 PM |
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the mounting of the fan can also have a huge impact on its apparent noise.
in exactly the same way as softer engine mounts reduce vibration in the rest of a car
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owelly
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| posted on 15/12/13 at 12:20 AM |
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Surely the noise is the volume of air being moved in order to flap the ribbons?!
http://www.ppcmag.co.uk
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rdodger
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| posted on 15/12/13 at 01:00 PM |
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The mounting of the current fan is a big part of it at the moment. The fan its self isn't so bad. I am currently bodging, orry engineering a
solution.
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MikeRJ
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| posted on 15/12/13 at 04:48 PM |
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quote:
Originally posted by owelly
Surely the noise is the volume of air being moved in order to flap the ribbons?!
Partly, which is why high airflow, small diameter fans are noisier than large ones (airspeed is higher), but you also get noise transmitted through
the frame which is greatly amplified if solid mounted. The quiet PC fans are mounted using very soft rubber "plugs" rather than screws.
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