USB Time Delay Fan Control

[Karaethon]

Hello All, Im trying to builda Time Delay Control for my computers Fan(s). My Computer doesnt get shut down often, but when it does the case temperature has spiked to as high as 60 degree C ( i usualy use F, but my case temp monitor is in C and I cant figure out how to change it) This is definitely NOT a good thing, So I decided to build a circut that will keep the fans spinning for a specific time after system shutdown (unless internal temp is still over a set limit). Now I'm a programmer, my electronics knowledge is a bit rudimentry, so I have no clue what I need to do this. Can anyone help me design this?

Oh, and one more thing, a few requirements.
#1 I dont want this taking up a USB port so I want it to plug into the USB pins on the motherboardand Have pins on it that allow me to plug the USB cable that would plug into the mother board into it.
#2 It must be able to monitor temp in the case, and make decisions based on the current temp
#3 I have to be able to set the Keep-Alive time from software.
#4 it needs to be able to monitor and alter fan speeds.

 

[Jay.slovak]

Why don't you just buy a PSU, that keeps its FAN on after the PC is shut down?(for couple minutes) That's a pretty elegant solution...

 

[akg]

I have to be able to set the Keep-Alive time from software.

this alone will increase the ckt complexity very much.

 

[Jay.slovak]

I have to be able to set the Keep-Alive time from software.

this alone will increase the ckt complexity very much.

Yes, it will. Simple potentiometer would do the job much easier.

 

[eblc1388]

Isn't the high temperature caused by having too much "standby" power drain from the standby 5V rail?

My suggestion is to connect a diode in series to the existing 12V cooling fan +ve wire of the power supply. This would enable the fan to run normally.

You then add another diode from the standby 5V to the fan +ve terminal also. Doing so would enable the fan to continue running at near 5V when the power supply goes into standby mode. Hopefully the slow running of the fan would cool the supply down to acceptable temperature.

A normal 12V fan may not run/start correctly when connected to 5V when idle but I guess it would continue to run once it has started.

 

[Karaethon]

Isn't the high temperature caused by having too much "standby" power drain from the standby 5V rail?

Actually no, when I first noteced this happening, I did a few tests, runt the comp for 12 hours then shutdown, and use a laser thermometer(a very handy devie for an overclocker) to find the source, and I found that the excess heat is from the Heat sinks(almost everything inside my case has em(CPU1&2,VidCard,Memory,HDDs,even the Audio card) and I found that when the fans run the sinks all hold at an "acceptable" temp (28-33 degrees C) but once the fans stop they all jump (i know this is actually a good thing, the heat is being pulled out, but its still bad for other compnents.

My suggestion is to connect a diode in series to the existing 12V cooling fan +ve wire of the power supply. This would enable the fan to run normally.

You then add another diode from the standby 5V to the fan +ve terminal also. Doing so would enable the fan to continue running at near 5V when the power supply goes into standby mode. Hopefully the slow running of the fan would cool the supply down to acceptable temperature.

I had originally thought to do something like this, but the more I thought about it The more I realized that this could actually be a marketable idea for other Modders/Overclockers so I started thinking of how I could add more user control to it.

A normal 12V fan may not run/start correctly when connected to 5V when idle but I guess it would continue to run once it has started.

I'd be inclined to agree with you, although this isnt neccisary as todays Intel P4 Motherboards have a always on 12V source for the P4 Chips.

akg wrote:

I have to be able to set the Keep-Alive time from software.

this alone will increase the ckt complexity very much.

Yes, it will. Simple potentiometer would do the job much easier.

I know that this circut will be fairly complex, But i figure it should be worth it, the ability to use a software "Frontend" with the circut will be a nice step above currently available solutions. there ARE "dumb" setps out there, they go inline with the Powersuppy and Fan and when the comp shuts off they keep supplying power to the fan for a preset amount of time, not much user control, use can choose one of like 3 time limits 3,5,10 mins. I want more.

 

[Someone Electro]

This means that your componets are at VERY high temp when operating but there is heat resistance so the meatsink is kept cold by the fan.This dosent sound good.

Did you check the PCs internal temp probles ? You can get to that whith some software or by going in to BIOS.So you get the temp of the CPUs core and so on

My tini ribs on the CPUs heatsink got once cloged up so not much air gould go trough and the CPU temp got up to 80 °C.Amazingly the PC continued to work normaly.

 

[Dan East]

the meatsink is kept cold by the fan.This dosent sound good.

I've heard of exotic methods of CPU cooling before, like liquid cooled, or even submersing the entire motherboard in oil, but meat is a new one to me.

Dan East

 

[Jay.slovak]

LOL, that's was a good one :lol:

Meatsink.... isn't that inhumane?

 

[akg]

I know that this circut will be fairly complex, But i figure it should be worth it, the ability to use a software "Frontend" with the circut will be a nice step above currently available solutions. there ARE "dumb" setps out there, they go inline with the Powersuppy and Fan and when the comp shuts off they keep supplying power to the fan for a preset amount of time, not much user control, use can choose one of like 3 time limits 3,5,10 mins. I want more.

Adding a s/w adjustable timer controlled using usb.?? is it worth the complexity??
or a potentiometer + comparator combo??

 

[JimB]

Am I being a bit thick and missing the point here, but, if the idea is to keep the fan running when the computer is shut down, why is USB and software being discussed.

Power off = computer not running any more, yes?

The obvious solution is as per Jays suggestion:

Why don't you just buy a PSU, that keeps its FAN on after the PC is shut down?(for couple minutes) That's a pretty elegant solution...

JimB

 

[akg]

Am I being a bit thick and missing the point here, but, if the idea is to keep the fan running when the computer is shut down, why is USB and software being discussed.

Power off = computer not running any more, yes?

JimB

No he needs to adjust the timeout parameter of the 'device' from s/w(prior to shutdown) & the interface using usb.

 

[Someone Electro]

That was an typo! LOL I meant heatsink by that.

But you should check your componets if it gets to 60 °C inside the case then there is most probobly somthing going over 70 °C and thats not good.

 

[Karaethon]

That was an typo! LOL I meant heatsink by that.

But you should check your componets if it gets to 60 °C inside the case then there is most probobly somthing going over 70 °C and thats not good.

Actually, my comp temps are GREAT during run, and thats the prob, My "Meatsinks" keep the CPUs at about 40° C During Power On, but once the fans sotp running the ambient temp insode the case Skyrockets cuz the sinks keep sinking the heat off the CPUs but the fans no longer are running to keep the air inside the case moving over them and out the back. (also, I've been considering Liquid cooling, but when I priced a liquid cooler setup for my specific need it was almost $300, a bit more than I'm willing to spend at the moment)

And yeah I know its a complex design, but i want control, and one thing ive learned is that the more you try to control something the more complex the system becomes, its a trade off, I could just use a POT and 555 but I dont want a "Dumb" circuit, I want something that can think and make decisions.

Also, on the "Meatsink" typo, I once was a Meatsink. I wasnt thinking about what I was doing, I had just replaced an Intel P3 chip and powered the machin eon without replacing the heatsink, I started smelling cooking chip and without thinking I placed my hand on the chip, I had the CPU Code info branded on my palm for a few weeks. damn things get HOT FAST! (if only my girl was like that...)

I've been thinking about the whole project, and I think I need to break it down into sections.
The questions I need answers to are:
What chip do I use to for the "brain"?
How Do I interface with this chip and USB?
How Do I count the pulses from the fans to determine the RPM speed, Pulses Per Minute or Milliseconds Between Pulses?(Pros and Cons of each?)
How do I alter Fan speed, Should I Regulate Fan Voltage, or Should I Modulate the 12v Feed?
How do I monitor ambient temp, I want to use 2 themocouples one for case ambient temp, and one for the exaust temp at the back of the case, I know I need an a/d converter but how do I use it?

 

[Jay.slovak]

I suppose you shouldn't play with "pure USB" as a beginner. Try serial or paralel port, or if you really want USB, try FTDI USB to serial transciever. Any PIC can handle what you need, the more FANs you want to control, the bigger PIC is needed (16F88 - 18pin 16F877 - 40pin 18Fxxxx -more_than_that). All new PICs have ADC onchip, this simplifies things a lot.

What are your experiences in PIC programming? I assume you can/want to use PIC

 

[Karaethon]

I suppose you shouldn't play with "pure USB" as a beginner. Try serial or paralel port, or if you really want USB, try FTDI USB to serial transciever. Any PIC can handle what you need, the more FANs you want to control, the bigger PIC is needed (16F88 - 18pin 16F877 - 40pin 18Fxxxx -more_than_that). All new PICs have ADC onchip, this simplifies things a lot.

What are your experiences in PIC programming? I assume you can/want to use PIC

well Im not completely new to USB, just never built my own USB devices before, and I was lookig at this one PIC, part PUC16F87X i think it was, came in a 44pin PLCC package, which I thought would be good. may not need all of it, but the PLCC makes it easy to swap out if it were to fail.(plus with all the old comps around my house I probably have a 44pin PLCC socket somewhere...(ahhh memories of 286 chips resurface...).
I gues PIC is what I need, like I said I'm a little light on this side of electronics, ive never really done anything with programable chips before. (well i did play with BASIC stamps in school but that was a while back and a bit Hazy now... )

But I am a fast learner, so learning how to do it shouldnt be a prob.

 

[Jay.slovak]

PUC16F877 is a good choice, make sure to read Nigel Goodwins tutorials as they use 16F877. Read the Sticky for more info.

 

[theinfamousbob]

Meatsink - the other way to prepare steaks.

Step One: Unwrap frozen meat product.

Step Two: Place on any computer component that would normally require a 'heatsink.'

Step Three: Monitor meat temperature until intended internal temperature is reached. Power down computer, pull off meat product, and enjoy!

For even more computational cooking, try our CPU Julienning machine! Puts the world-renowned Salad-Shooter to shame!

I couldn't resist. :lol:

 

[Someone Electro]

You are not geting it.

If the case temp goes to 60 °C than there must be somthing in there that is well above 60 °C (Not good).If evrything in the case is bwlow 40 °C the case temp should NEVER get above 40 °C.Unles you have an heat pump inthere to suck the heat off the components unteil they freze.

Heat wont flow from cold to hot!

 

[Karaethon]

You are not geting it.

If the case temp goes to 60 °C than there must be somthing in there that is well above 60 °C (Not good).If evrything in the case is bwlow 40 °C the case temp should NEVER get above 40 °C.Unles you have an heat pump inthere to suck the heat off the components unteil they freze.

Heat wont flow from cold to hot!

I do undertsand, if there is no airflow across the heatsink then the temp is high, I was using software, something called EVEREST, and it reports my CPU's temps as 51°C each, and that is with the fans on, when I shut the fans off it began climbing, i turned them back on when it hit 65 and didnt seem to be stopping, when the came up to speed the temp dropped fast. this is what i've been trying to say, when the system shuts offand the fans stop the latent heat in the CPU keeps being pulled out by the heatsinks but without the airflow the heat lingers inside the case instead of being pulled out the exhaust port in the back. I dont have replacement CPUs (they arnt cheap) so I dont want to find out their max operating temp, but im positive that withot thefans they would run well above 60°C( I woner if they would hit 100°C and still run or die before then.)