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The shroomy 1
Luminous beings surround me




Registered: 03/27/07
Posts: 5,543
Loc: The Aether
Last seen: 5 months, 5 days
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Re: How would I reduce the speed of a 12VAC 3AMP for my humidifier? [Re: yepyepyep]
#7633388 - 11/13/07 11:46 PM (16 years, 2 months ago) |
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I feel you guys make it too hard! If the fan is blown, next time buy a AC fan. They're not that much more that expensive than the DC ones. Then go to Home Depot and buy a dimmer . A little soldering and your done! If you don't want to buy the AC fan, then just cut the wire leading from the transformer to the wall outlet and put the dimmer in between. I use this same set up for my magnetic stirrer and I have full control of the magnetic stirrer speed.
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AMU Q&A thread.
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psycho_bin_farma
Hobbyist




Registered: 04/20/07
Posts: 171
Last seen: 13 years, 2 months
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Re: How would I reduce the speed of a 12VAC 3AMP for my humidifier? [Re: The shroomy 1]
#7633406 - 11/13/07 11:52 PM (16 years, 2 months ago) |
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awwwwwwwww, my original fan was AC. that would have been awesome. thanks for the tip tho.
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Sillicybin
Registered: 02/14/05
Posts: 2,134
Loc:
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Re: How would I reduce the speed of a 12VAC 3AMP for my humidifier? [Re: psycho_bin_farma]
#7633954 - 11/14/07 07:12 AM (16 years, 2 months ago) |
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The best way to reduce fan speed on brushless DC motors is with pulse-width modulation, and that requires a number of components and a little electronics know-how. There are schematics available on the internet, just search for "PWM fan controller." You can even go so far as to put it on a microcontroller-based timer to switch it on/off at selected intervals, or if you want to be REALLY complicated, based it on a sensor that measures CO2 levels and controls fan speed accordingly.
Most 12VDC motors can run on 6VDC and it will reduce speed, but some will fail to start from a stop at that voltage.
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Yoschie99
nomad



Registered: 11/24/99
Posts: 3,149
Loc: center of earth
Last seen: 2 months, 17 days
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Re: How would I reduce the speed of a 12VAC 3AMP fan for my humidifier? [Re: psycho_bin_farma]
#7633989 - 11/14/07 07:40 AM (16 years, 2 months ago) |
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I didn't read all the replies, so sorry if i'm repeating someone.
agar has a ton of info on this somehwere on the site, but I believe what you want to do is replace teh transformer w/ one for a smaller fan... something that's only giving you about 1/4 the output that you have now, hence only running your fan at quarter-speed.
I have no personal experience with this, though... i suggest doing a search through agar's posts on building these things.

yos-
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mycocurious
Mike O. Kuerias



Registered: 02/09/07
Posts: 1,265
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Re: How would I reduce the speed of a 12VAC 3AMP fan for my humidifier? [Re: Yoschie99]
#7634030 - 11/14/07 08:08 AM (16 years, 2 months ago) |
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personally, i used a 120V / 0.5 AMP AC (shaded pole) blower for my humidifier's fan because they're (some, not all, check) actually rated for continual use under static pressure, or "back pressure", caused by attempting to blow a large volume of air into a small compartment. The high the static pressure the more resistance is applied to the axis which results in more amperage being supplied in order to force the blades to keep turning...which causes additional friction and - unless your fan is rated for it - can burn out the motor or start a fire.
Or I might just be paranoid, I treat electricity and electronics like magic. I know just enough to respect it immensely but not enough to be willing to bend the rules to meet my whims...well, in most cases.
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Don't mistake my tone for a "matter-of-fact" attitude. I'm just presenting what I believe to be correct, until I'm corrected... - How Myco-Curious Prepares Coir & Compost Substrates - How Myco-Curious Builds A Bulk Humidifier - How Myco-Curious Builds An Automated Greenhouse ------------------------------------ figgusfiddus said: Keep in mind that inoculating or whatever in front of a flow hood won't help your bad substrate, your bad inoculant, your bad sterile procedure, etc. etc. etc. It's not a +3 flowhood of magic, it's just a tool.
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RogerRabbit
Bans for Pleasure



Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 11 months, 3 days
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Re: How would I reduce the speed of a 12VAC 3AMP fan for my humidifier? [Re: mycocurious]
#7634184 - 11/14/07 09:23 AM (16 years, 2 months ago) |
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NEVER use a lighting dimmer to control speed of an AC motor. That is not only a very dangerous fire hazard, but it will burn up the motor in short order. AC motor speed is controlled by the frequency, which in the US is 60 hz, and in most of Europe is 50 hz. AC motors are not controlled by current, which should be steady. In addition, it's a violation of the National Electrical Code to use them for motor control, so any licensed electrician that hooks one up would lose his license for sure. In fact, an electrician was charged with 2nd degree murder in New York recently for hooking up a ceiling fan to a lighting dimmer, which then caused a fire that killed two children. NEVER do it please. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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