reducing fan speed help.

Thread Starter

frank55

Joined Dec 6, 2013
286
Hi guys; hope you have a Happy New year;

i have here a dehumidifier air purifier that i found almost new that i would like to use in the bad room.but there is a drawback it makes too much noise even on low speed for me that i can't go sleep,it has a switch with speed 1 and 2 and off,
is there a way i can reduce by half the lower speed,i was thinking of putting a resistor but i don't know how much ohms i should use,
i have here an example see link;but this is for 12v fan,i need for 120v fan.
any suggestion would be appreciated,thanks.


http://www.pcbheaven.com/circuitpage..._DC_Fan_Speed/
 

wayneh

Joined Sep 9, 2010
16,398
On most dehumidifiers, the noise comes more from the compressor coming on an off than from the blower fan, and you can't do anything about that. Are you certain it's the blower fan making the noise? You MIGHT be able to use a typical light switch dimmer - wired internally to just the fan - to slow it a little but keep in mind that it cannot dehumidify without moving air over its coils.
 

Dr.killjoy

Joined Apr 28, 2013
1,196
You could try some sound dampening .. Over the years I have had a couple units and never had one that was quite.. Oh you could put the unit on a timer so when you sleep the unit will be off and come on automatically when your awake..
 

Alec_t

Joined Sep 17, 2013
11,417
i was thinking of putting a resistor but i don't know how much ohms i should use,
That isn't a very practical method for a 120V motor. A phase-controlled switch (such as is used in a lamp dimmer, as Wayneh mentioned) rated for inductive loads might be better, but induction motors run from mains don't take kindly to be slowed drastically.
 

Dr.killjoy

Joined Apr 28, 2013
1,196
That isn't a very practical method for a 120V motor. A phase-controlled switch (such as is used in a lamp dimmer, as Wayneh mentioned) rated for inductive loads might be better, but induction motors run from mains don't take kindly to be slowed drastically.
Would the compressor kicking on and off or not enough to start or just stall cause a potential fire issue??
 

wayneh

Joined Sep 9, 2010
16,398
The compressor circuit must not be tampered with, only the fan. So the dimmer could not just be added on externally.
 

Alec_t

Joined Sep 17, 2013
11,417
A simple diode (600 V and an amp or two) would cut the power in half because it would work only on have of the sine wave from mains power.
That would more likely cut the power completely! The motor would burn out because of coil saturation. AC induction motors don't like a nett DC current.
 

mcgyvr

Joined Oct 15, 2009
5,394
trash it and pick up a safety 1st ultrasonic humidifier.. ~$30 and done and virtually silent compared to cool mist types..
 

BR-549

Joined Sep 22, 2013
4,938
Can you show us a picture of the unit? Or a link to the EXACT unit?

Is it a Humidifier or a Dehumidifier?

Is your bedroom too wet or too dry?
 
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