This question may reveal my utter newbieness when it comes to fans and fan control, but I've been searching and looking around, and can't really find any threads answering my question, so here goes:
I keep reading about various ways to undervolt a fan to 7V or 5V, thus making it spin slower, but what if I want to make it stop completely? Short of opening the case and unplugging the fan's power connector, or getting one of those big 5.25"-bay fan controllers with on-off toggles, what options do I have?
Ideally, I'd like the fan to stop automatically when the CPU temp is below a certain level. My mobo seems to support various ways of lowering the speed dynamically (both Asus Q-Fan2 and AMD Cool 'n' Quiet). Is there any way I can modify this behavior to make it stop the fan completely? Could I, for instance, insert a resistor that would make it spin very slowly when receiving max power from the mobo and not at all when receiving the lowest setting?
The fan, if it matters, would be a Nexus 120mm Real Silent.
How about stopping a fan completely?
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datapappan
- Posts: 199
- Joined: Wed Nov 10, 2004 1:44 pm
- Location: Sweden
Good question! This way your system will surely be quiet when idling/low loaded.
First, how much modding are you prepared to do? You would probably need a custom resistor fitted in order to take down the voltage @ slow speed below 4V, where many fans stop spinning, let alone start. Don't know the limit for Nexus, it's rated down to 6.8V, but most fans can go lower if they are already spinning.
The mobo output is usually of the PWM sort, meaning 60% speed is actually 12V put out in a square wave with 60% 12V/40% 0V. This means the fan might start when modded to go below say 4V, because it's actually seeing maybe 8V, albeit flickering - enough to kick the fan into stable spin. To overcome this a capacitor/attenuator must be fitted to even out the square wave, and getting the real voltage below your starting limit.
Either that, or build a thermostat with an NTC-resistor and an op-amp for threshold function, see www.cpemma.co.uk or www.7volts.com for more pointers.
/ datapappan
First, how much modding are you prepared to do? You would probably need a custom resistor fitted in order to take down the voltage @ slow speed below 4V, where many fans stop spinning, let alone start. Don't know the limit for Nexus, it's rated down to 6.8V, but most fans can go lower if they are already spinning.
The mobo output is usually of the PWM sort, meaning 60% speed is actually 12V put out in a square wave with 60% 12V/40% 0V. This means the fan might start when modded to go below say 4V, because it's actually seeing maybe 8V, albeit flickering - enough to kick the fan into stable spin. To overcome this a capacitor/attenuator must be fitted to even out the square wave, and getting the real voltage below your starting limit.
Either that, or build a thermostat with an NTC-resistor and an op-amp for threshold function, see www.cpemma.co.uk or www.7volts.com for more pointers.
/ datapappan
Thanks for a very good reply - tells me this is quite a bit more complicated than I was hoping for, the difficult part being the capacitor/attenuator thing you mention. You say "usually" and "might", though, so maybe there's a chance I'll get the desired effect simply with some combination of off-the-shelf resistors or voltage regulators? I'll look into the more technically challenging solution, but it sounds like something I'd need pretty specific instructions for in order to pull off.
Barring that, is there some simple solution that would let me manually toggle a fan on/off by either flicking a switch on the outside of the case, or through software? (Actually, if there was just some way to turn a fan on and off through software, under Linux, I could write the necessary logic for hooking it to the temperature sensors myself.)
Barring that, is there some simple solution that would let me manually toggle a fan on/off by either flicking a switch on the outside of the case, or through software? (Actually, if there was just some way to turn a fan on and off through software, under Linux, I could write the necessary logic for hooking it to the temperature sensors myself.)
If you don't mind doing a bit of minor surgery on your fan wires, why not just snip the red wire, strip the two loose ends and wire an off-the-shelf switch in between? You could buy a suitable switch for 50p in Maplin if you're in the UK, otherwise whatever your local equivalent is. Probably wouldn't even need soldering if you buy the right switch.
Alternatively, if the fan is attached to a header on the motherboard you could use some software like Speedfan to control the fan speed. I think it goes all the way down to zero if you want the fan to stop entirely, and you can set it to ramp up if your CPU/North Bridge/Hard Drives get too hot. Although this may be a windows-only solution, not sure. Might work in the WinE emulator?
Hope this helps,
Al
Alternatively, if the fan is attached to a header on the motherboard you could use some software like Speedfan to control the fan speed. I think it goes all the way down to zero if you want the fan to stop entirely, and you can set it to ramp up if your CPU/North Bridge/Hard Drives get too hot. Although this may be a windows-only solution, not sure. Might work in the WinE emulator?
Hope this helps,
Al
you should be able to do what you want using speedfan, you will need the motherboard headers to support speed control, but this usually works with q-fan asus boards (on at least one fan header). you turn Speed01, say, down to 0% and the fan coupledf to that variable will switch off (actually, with the nexus fan, it will probably stall anywhere <50%). you can also set up automatic fan speed control as function of a temperature using this program.
oops - you mentioned linux in your second post, well i don't know about that! but at least you know it's theoretically possible now...
oops - you mentioned linux in your second post, well i don't know about that! but at least you know it's theoretically possible now...
A Macpower Digital Doc 5+ will start and stop the fans completely in response to temperature readings. Ironically this is usually considered a negative, because what the DD5+ can't do is fan speed (voltage) control. It's on or off only. So maybe if you want to get creative there has to be a way to use it to output a reduced voltage in the end... maybe something as simple as wiring a fan controller inline after the DD5+ but before the fans. (Just my theory!)
I hear very good things about the T-balancer, but I know very little about its use, as it sounds too complicated (and expensive?) for my tastes. I'd prefer devices like this to be more hardware-based. I believe it can stop fans and do whatever else you'd like though.
I hear very good things about the T-balancer, but I know very little about its use, as it sounds too complicated (and expensive?) for my tastes. I'd prefer devices like this to be more hardware-based. I believe it can stop fans and do whatever else you'd like though.
lm_sensors has a shell script called fancontrol. Also, an extract from lm_sensors/pwmconfig:
Cheers,
Jan
Perhaps this would help?It attempts to briefly stop each fan using the PWM controls.
Cheers,
Jan