Fan Speed Control
Im looking for a fan speed control. Please dont post your internet search results here. Anyone, including me, can do a search and find mindless stuff. I am looking for specific knowledge, thanks ...
Forum Discussion
I've been a bit of a fan and ventilation enthusiast for years now.
Of all the fans I run, only one, is run by a PWM motor speed controller.
That one is powering the brushed motor of my vehicles Hvac system. It is 21 kHZ and is rated for 40 amps. I bypass the stock resistor packs, gain much more wide range of fan speeds, and can turn it on with no key in ignition.
I've used it powering powerful computer fans and it works well, but it draws slightly more current than using a voltage controller to control the computer fan speed.
A lot of computer fans are 4 wire PWM fans, and the 4th wire is to be sent a PWM signal from the computer motherboard in order to control fan rpm.
Noctua has a NA-fc-1 speed controller that makes it relatively easy to control such fans, and I used to use it to control Noctua's IPPC NF-f12 3k rpm 120mm fans and their 140 IPPC version too. I had tremendous failure rates of these fans, and Noctua was excellent about warranty replacements, and sending shipping labels for returning the fans so they could investigate failure mode, but ultimately all these fans have failed.
Before this Noctua speed controller came out, I cobbled together a 555 PWM signal generator, and achieved full function, but it was clunky as I had to feed the signal generator 5v, not 12v.
As an experiment I tried to just use the 3 amp voltage bucker( lm2596 based), to speed control the fan, and it worked quite well. No whining at reduced speeds, and could slow the fan even more than when a PWM signal was fed via the fourth wire. comparing the amp draw at similar fan noise/speed/flow, revealed controlling fan speed via voltage bucker was more slightly efficient than a PWM signal generator.
I then tried the voltage bucker as a LED dimmer. It was way better than the cheapo LED dimmers I had been using. absolutely no flickering and would dim the lights much lower, to tiny pinpricks of light at nearly unmeasurable amp draw.
I found there were similarly sized XL 4005 or xl4015 based voltage buckers which are rated at 5 amps.
when fed 12v, the max output voltage of the lm2596 bucker is ~11.35v
when fed 12v the max output voltage of the xl4005 is 11.69v
when fed 12v the max output voltage of the xl4015 is 11.81v.
So ALL my leds are now dimmed by either the xl 4005 or xl4015 buckers. LEDs can whine on PWM motor speed controllers, and they can flicker.
Mine dim to lower levels and never flicker on the voltage buckers.
These buckers require removing the tiny voltage trimpot and adding wires to a larger potentiometer for simple finger twist voltage/speed control.
some of these voltage buckers have two potentiometers, one for voltage one for current. Both work for controlling fan speed, led brightness, but I found voltage control to work better each time I compared. I also found the buckers with current control pots to not only be slightly more expensive but less reliable.
My strategy with computer fans evolved to finding insanely powerful fans, and using voltage buckers to speed control them. I will use two potentiometers, one ( the tiny trimpot the buckers some with), inline with a finger twist, to keep it from going below a certain voltage where the fan does not spin.
This minimum voltage ranges from 3 to 7 volts depending on the fan, and voltage required to get impeller spinning is usually 1 to 1.5v over this minimum rpm voltage.
I also employ some 24vdc fans, and use a voltage buck/boost converter to speed control them.
I like Delta brand computer fans, but beware there are clones and counterfeits out there, some of which still work quite well, but I can tell the build quality is less, and the blade balance is worse.
If one does go the computer fan route, their biggest failure point is the solder joints where the wires enter the hub. I recommend peeling up the sticker on the hub and covering these joints with dielectric grease, or something like Amazing goop.
Some of the fans, the wires are routed a bit differently to the hub, and enter the underside, and one needs to remove the impeller with some c clip pliers to access the circuit board.
Most of the fans at minimum speed are well below 0.1 amp, even through a buck boost converter or just a buck converter, and quiet enough that I sleep with them inches from my head.
I would recommend high rpm 120 or 140mm fans. 38mm thick.
Those with stator blades/ hub support keep the fan's flow a narrow dense column, not important for an exhaust fan, but great for interior circulation.
the CFm ratings of fans is misleading, as the cfm figure is not actually measured by the volume of air moved, the speed of the air is measured and the diameter and some math is performed.
Fans with just 4 hub supports usually have 4 'hotspots' of airflow, and the velocity of these hotspots is not representative of the total aperture.
Static pressure ratings is another way to measure fans flow, and is more important when there is a restriction to flow, such as when it is trying to exhaust a closed bathroom or push air into a finned heatsink.
I have achieved much better balance of some fan impellers using an accellerometer app on my smartphone, and some trial and error. These improved balance fans make less noise and can spin faster for the same voltage applied.
My favorite fans a few years back were made by silverstone, as some models would come with a built in fingertwist speed control. the fm 121 and the 181, and the AP182.
The AP182 hated charging voltages though.
n
Of all the fans I run, only one, is run by a PWM motor speed controller.
That one is powering the brushed motor of my vehicles Hvac system. It is 21 kHZ and is rated for 40 amps. I bypass the stock resistor packs, gain much more wide range of fan speeds, and can turn it on with no key in ignition.
I've used it powering powerful computer fans and it works well, but it draws slightly more current than using a voltage controller to control the computer fan speed.
A lot of computer fans are 4 wire PWM fans, and the 4th wire is to be sent a PWM signal from the computer motherboard in order to control fan rpm.
Noctua has a NA-fc-1 speed controller that makes it relatively easy to control such fans, and I used to use it to control Noctua's IPPC NF-f12 3k rpm 120mm fans and their 140 IPPC version too. I had tremendous failure rates of these fans, and Noctua was excellent about warranty replacements, and sending shipping labels for returning the fans so they could investigate failure mode, but ultimately all these fans have failed.
Before this Noctua speed controller came out, I cobbled together a 555 PWM signal generator, and achieved full function, but it was clunky as I had to feed the signal generator 5v, not 12v.
As an experiment I tried to just use the 3 amp voltage bucker( lm2596 based), to speed control the fan, and it worked quite well. No whining at reduced speeds, and could slow the fan even more than when a PWM signal was fed via the fourth wire. comparing the amp draw at similar fan noise/speed/flow, revealed controlling fan speed via voltage bucker was more slightly efficient than a PWM signal generator.
I then tried the voltage bucker as a LED dimmer. It was way better than the cheapo LED dimmers I had been using. absolutely no flickering and would dim the lights much lower, to tiny pinpricks of light at nearly unmeasurable amp draw.
I found there were similarly sized XL 4005 or xl4015 based voltage buckers which are rated at 5 amps.
when fed 12v, the max output voltage of the lm2596 bucker is ~11.35v
when fed 12v the max output voltage of the xl4005 is 11.69v
when fed 12v the max output voltage of the xl4015 is 11.81v.
So ALL my leds are now dimmed by either the xl 4005 or xl4015 buckers. LEDs can whine on PWM motor speed controllers, and they can flicker.
Mine dim to lower levels and never flicker on the voltage buckers.
These buckers require removing the tiny voltage trimpot and adding wires to a larger potentiometer for simple finger twist voltage/speed control.
some of these voltage buckers have two potentiometers, one for voltage one for current. Both work for controlling fan speed, led brightness, but I found voltage control to work better each time I compared. I also found the buckers with current control pots to not only be slightly more expensive but less reliable.
My strategy with computer fans evolved to finding insanely powerful fans, and using voltage buckers to speed control them. I will use two potentiometers, one ( the tiny trimpot the buckers some with), inline with a finger twist, to keep it from going below a certain voltage where the fan does not spin.
This minimum voltage ranges from 3 to 7 volts depending on the fan, and voltage required to get impeller spinning is usually 1 to 1.5v over this minimum rpm voltage.
I also employ some 24vdc fans, and use a voltage buck/boost converter to speed control them.
I like Delta brand computer fans, but beware there are clones and counterfeits out there, some of which still work quite well, but I can tell the build quality is less, and the blade balance is worse.
If one does go the computer fan route, their biggest failure point is the solder joints where the wires enter the hub. I recommend peeling up the sticker on the hub and covering these joints with dielectric grease, or something like Amazing goop.
Some of the fans, the wires are routed a bit differently to the hub, and enter the underside, and one needs to remove the impeller with some c clip pliers to access the circuit board.
Most of the fans at minimum speed are well below 0.1 amp, even through a buck boost converter or just a buck converter, and quiet enough that I sleep with them inches from my head.
I would recommend high rpm 120 or 140mm fans. 38mm thick.
Those with stator blades/ hub support keep the fan's flow a narrow dense column, not important for an exhaust fan, but great for interior circulation.
the CFm ratings of fans is misleading, as the cfm figure is not actually measured by the volume of air moved, the speed of the air is measured and the diameter and some math is performed.
Fans with just 4 hub supports usually have 4 'hotspots' of airflow, and the velocity of these hotspots is not representative of the total aperture.
Static pressure ratings is another way to measure fans flow, and is more important when there is a restriction to flow, such as when it is trying to exhaust a closed bathroom or push air into a finned heatsink.
I have achieved much better balance of some fan impellers using an accellerometer app on my smartphone, and some trial and error. These improved balance fans make less noise and can spin faster for the same voltage applied.
My favorite fans a few years back were made by silverstone, as some models would come with a built in fingertwist speed control. the fm 121 and the 181, and the AP182.
The AP182 hated charging voltages though.
n
