Low RPM Ventilation

[gothicsurf]

In pursuit of ventilation for cooking in a truck camper, I am looking at using a couple 120-140mm computer case fans because of their thin profile and relatively quiet operation. To have the option of operating them at a minimal RPM would be a bonus.

It seems relatively simple finding and connecting the fan motor's 12V leads, though not as sure about having a rotary/dimmer switch in line. I understand fans generally need a certain amount of current to break free of being static in a magnetic field. 

Most specs for these fans have a range that looks like 600-1200 rpm with the lower end a full half their maximum. I have been told PWM fans may be able to better adapt to lower rpms because of the intended application of variability, but do not respond well to decreased voltage in favor of pulse-width modulation for adjustment. Non-PWM fans however have no problem with variable voltage but may not be built for RPMs as low as PWM fans.

Anyone else out there with experience using these for their ventilation needs?

 

[abnorm]

SternWake was a member here for many years..........

Here's his thread (23 pgs) on a different vanning forum about controlling computer fans

https://vandwellerforum.com/thread-131.html

""Tales from a Ventilation Lunatic""

 

[user 423]

I'm using a Silverstone FM 121 fan that is 11 years old and sometimes runs nearly 24 hrs/day.

3 years ago I bought another one as a backup but just recently found out that it doesn't work. Long past the Amazon return date.

 

[bagabum]

option of operating them at a minimal RPM would be a bonus.

 

[jonyjoe303]

I use 12 volt 120mm case fans on my swampcoolers, they are all about the same. You can use a pwm motor controller to control the rpm and I also have been using a small buck converter where I don't need to make constant speed adjustments, either will work. Most 120mm cooler fans are less then 1.5 amps to operate. Some fans have more then 2 wires, but you only need the red and black, thats all I ever use to control speed. With either of these methods you reduce the rpm to where the rpm is extremely low just barely producing any airflow and very quiet.

buck converter 3 amp (about 3 dollars) You need a small screwdriver to adjust the rpm.


dc pwm controller 10 amp (about 6 dollars) this can handle the small 120mm fans and also power one of the larger car radiator fans. You can adjust the speed quickly with the large knob.

 

[gothicsurf]

no need for the fourth wire on these PWM fans?

 

[MrNoodly]

Why low RPM?

 

[jonyjoe303]

Why low RPM? low rpm is to reduce noise, even the small 40mm fans I use on my buck converters make a racket at full speed. The 120mm fan I use to vent my fridge runs all night, I reduce the rpm to the minimum required to do the job, I don't even hear it at night. I also added a buck converter to the small fan on my 200 watt ac inverter, it was too loud when running at full speed, which isn't needed when only using 50 watts.

I' m not sure which fans are pwm or non-pwm, all the computer cooling fans I used worked with the pwm controller and buck converter, all the extra wires on the fans I just cut off and only use the red and black wires.

 

[MrNoodly]

Why low RPM? low rpm is to reduce noise,...

Ah, okay. I have tinnitus and nerve deafness, so I never hear small fans. Either they're at a pitch I just can't hear, or the constant screeching in my head is louder.