Using PWM fans to cool a Media Cabinet

[rikg09]

Hi I just thought I'd start this by saying that I'm an absolute beginner to electronics, and the furthest I've really done is build my own gaming PC. But I'm willing to learn and try everything

 

So the problem I have is that my parents bought this really fancy media cabinet and in it we have our XBOX, TV Box, DVD Player and our AV Receiver. The issue is that it boils in there, and sometimes the box's stop working and need to be cooled down. Right now we just leave the doors open at the front, and usually this is fine, but I want to make some holes at the back and fit some PWM fans for intake and exhaust to try and get some of the hot air out of there.

 

I've got 2 Corsair PWM fans that came with a pc component that I didn't need, and I'm planning to buy 2 more if I can figure out how to do this. I want to be able to vary the fan speed so I can have it at low noise most of the time, and then ramp it up if it gets really hot. 

 

I have a raspberry pi, and I tried searching online to find guides and such, but all of it seemed beyond me and the terminology left me more confused when I started.

 

I'm really hoping any of you can point me in the right direction and help me out.

 

Thanks in advance, and sorry if i've put this post in the wrong place, or if I'm missing something incredibly obvious. 

[almondhive]

 

Actually Linus did a couple of videos dealing with a very similar problem. I'll leave you the links or you can search for Linus tech tips - Entertainment Center Cooling Mod on yotube. Hope it helps.

 

 

 

[rikg09]

9 minutes ago, almondhive said:

 

Actually Linus did a couple of videos dealing with a very similar problem. I'll leave you the links or you can search for Linus tech tips - Entertainment Center Cooling Mod on yotube. Hope it helps.

 

 

 

 

Hi thanks for the reply

 

Yeah I saw this, and that's where I originally got the idea. The issue is that I don't have a full proper computer there to manage the PWM fans. I could use a the Raspberry Pi for it, but I have no idea how. 

 

[almondhive]

Oh ok, well i don't have a lot of experience on PWM fans but this are some ideas that come to my mind.

 

1) I've seen somewhere (I will search where) someone made a PWM fan controller with an Arduino, some PWM fans and a temperature sensor. I've never programmed an Arduino and I don't know how difficult it is but maybe its a solution. You also mentioned you have a raspberry Pi, i think it is also possible to control the fans with it but i've never done it. 

 

2) Another idea is to build a manual PWM controller like the one here: http://www.overclockers.com/pwm-fan-controller/ and use it to control your fan manually.
If you don't want the hassle of building it from scratch like on that guide i would search for it on ebay for a PWM fan controller, maybe there is one already made with temperature sensor and free shipping from china :0 .

 

3) Once I had a noisy fan on my case and it wasn't a PWM fan so I couldnt control the speed from my motherboard, so I built a low noise adapter with a resistor to lower the voltage from 12V to 7ish Volts. My point is: maybe you could wire a fan like in this guide i found http://www.silentpcreview.com/article6-page1.html and then connect the fan to an external 12 V power supply that plugs directly into the wall. You won't have a temperature controlled fan but you can have a simple switch controlling your fan from 12v, 5v or off depending on your needs of cooling and noise.

Now I see some shortcomings that must be solved in order for this idea to work: First of all I don't know what's the effect of changing the input voltage of a PWM fan, i've only tried it with non-pwm controlled fans and I suspect there must be some problem with doing that with pwm. Second, the silentpc guide I linked earlier assumes you are connecting to a molex power connector so you have 12V, ground, ground, 5V in the pins. In order for this to work with only a 12v wall plugged power supply we need to somehow with a switch and some resistors to lower the voltage. 

 

Hope it helps, sounds like a fun project.

Daniel F.

[GnuHandel]

If you're interested in learning how to set up PWM controls from a raspberry Pi, Adafruit has a set of tutorials which you should check out here (and remember, a fan is just a motor whose load is the air it pushes). Keep in mind though, you're going to need more than just PWM to make this project work.

 

You're also going to need a protection/step up circuit and a 12V source of power for the fan (since the RPi doesn't supply enough voltage to run the fan, and you don't want the fan to wreck your board) as well as a sensor and circuit that will allow you to record whatever is going on in your case that you want the fans to respond to (temperature, power going through a cable, etc.)

 

You'll end up modifying the Adafruit codes to create a basic program that reads from the sensor, selects a duty cycle for the fan based on how you want the fan to run, and sends that duty cycle to the protection circuit, which will run the fan.

 

This is a great project to get you started with sensors and coding in python, but if it seems like a bit much, you can always just pick up a 12V PWM PC fan speed controller and a 12V power bar  for $5-20USD on ebay.

 

Hope this helps! If you go the PWM route and want some help with terms, feel free to message me.

 

[Huntsman]

I get your idea but honestly do you really have to use the rpi? To me this is the sort of problems that can be solved easily without spending that much.

 

Assuming that what you're trying to do is just to control fan speed with respect to temperature, something like this would have worked and everything would cost a few bucks at most.

 

Or if you're itching for a challenge, you could learn a some microcontroller codings and whip up a solution with more bells and whistles than there are grass in a field.

 

OR you could do it the lazy way and plug the fan directly to your motherboard FAN headers... set the fan to "track" ambient temperature..

[rikg09]

17 hours ago, almondhive said:

Oh ok, well i don't have a lot of experience on PWM fans but this are some ideas that come to my mind.

 

1) I've seen somewhere (I will search where) someone made a PWM fan controller with an Arduino, some PWM fans and a temperature sensor. I've never programmed an Arduino and I don't know how difficult it is but maybe its a solution. You also mentioned you have a raspberry Pi, i think it is also possible to control the fans with it but i've never done it. 

 

2) Another idea is to build a manual PWM controller like the one here: http://www.overclockers.com/pwm-fan-controller/ and use it to control your fan manually.
If you don't want the hassle of building it from scratch like on that guide i would search for it on ebay for a PWM fan controller, maybe there is one already made with temperature sensor and free shipping from china :0 .

 

3) Once I had a noisy fan on my case and it wasn't a PWM fan so I couldnt control the speed from my motherboard, so I built a low noise adapter with a resistor to lower the voltage from 12V to 7ish Volts. My point is: maybe you could wire a fan like in this guide i found http://www.silentpcreview.com/article6-page1.html and then connect the fan to an external 12 V power supply that plugs directly into the wall. You won't have a temperature controlled fan but you can have a simple switch controlling your fan from 12v, 5v or off depending on your needs of cooling and noise.

Now I see some shortcomings that must be solved in order for this idea to work: First of all I don't know what's the effect of changing the input voltage of a PWM fan, i've only tried it with non-pwm controlled fans and I suspect there must be some problem with doing that with pwm. Second, the silentpc guide I linked earlier assumes you are connecting to a molex power connector so you have 12V, ground, ground, 5V in the pins. In order for this to work with only a 12v wall plugged power supply we need to somehow with a switch and some resistors to lower the voltage. 

 

Hope it helps, sounds like a fun project.

Daniel F.

Thanks for the reply.

 

What you've said is a lot of help. I think I'm going to look into the Arduino and see what I can find

 

[rikg09]

17 hours ago, GnuHandel said:

If you're interested in learning how to set up PWM controls from a raspberry Pi, Adafruit has a set of tutorials which you should check out here (and remember, a fan is just a motor whose load is the air it pushes). Keep in mind though, you're going to need more than just PWM to make this project work.

 

You're also going to need a protection/step up circuit and a 12V source of power for the fan (since the RPi doesn't supply enough voltage to run the fan, and you don't want the fan to wreck your board) as well as a sensor and circuit that will allow you to record whatever is going on in your case that you want the fans to respond to (temperature, power going through a cable, etc.)

 

You'll end up modifying the Adafruit codes to create a basic program that reads from the sensor, selects a duty cycle for the fan based on how you want the fan to run, and sends that duty cycle to the protection circuit, which will run the fan.

 

This is a great project to get you started with sensors and coding in python, but if it seems like a bit much, you can always just pick up a 12V PWM PC fan speed controller and a 12V power bar  for $5-20USD on ebay.

 

Hope this helps! If you go the PWM route and want some help with terms, feel free to message me.

 

Thanks for the help, I do want to learn about sensors and start coding in python so I think I'll take a look into the Adafruit tutorials. Thanks for pointing me in the right direction.

[rikg09]

1 hour ago, Huntsman said:

I get your idea but honestly do you really have to use the rpi? To me this is the sort of problems that can be solved easily without spending that much.

 

Assuming that what you're trying to do is just to control fan speed with respect to temperature, something like this would have worked and everything would cost a few bucks at most.

 

Or if you're itching for a challenge, you could learn a some microcontroller codings and whip up a solution with more bells and whistles than there are grass in a field.

 

OR you could do it the lazy way and plug the fan directly to your motherboard FAN headers... set the fan to "track" ambient temperature..

Thanks for the reply. I only mentioned the Pi because I already have one that I was using for a NAS. I don't really use it anymore, and I just thought it would help if I mentioned it. 

I don't have a motherboard where the Media Cabinet is, and I don't really want to put anything bulky there. Hence why I was thinking about the RPi

[Huntsman]

4 hours ago, rikg09 said:

Thanks for the reply. I only mentioned the Pi because I already have one that I was using for a NAS. I don't really use it anymore, and I just thought it would help if I mentioned it. 

I don't have a motherboard where the Media Cabinet is, and I don't really want to put anything bulky there. Hence why I was thinking about the RPi

Then just a 555 circuit would do fine.. If you're good with soldering, the entire thing can be the size of a dime.

[DragonTamer1]

I just finished a fan controler circuit for my computer case that I can post. I was planning on making a new thread for it after I had sourced all the parts to simplify things.

 

 

As it's shown in this schematic it can only drive a single fan for the time being. Some parts will need to be modified depending on your fan. It can be expanded to accommodate more fans but I don't have the schematic prepared for that yet.

[rhyseyness]

On 8/13/2016 at 7:21 PM, DragonTamer1 said:

I just finished a fan controler circuit for my computer case that I can post. I was planning on making a new thread for it after I had sourced all the parts to simplify things.

 

 

As it's shown in this schematic it can only drive a single fan for the time being. Some parts will need to be modified depending on your fan. It can be expanded to accommodate more fans but I don't have the schematic prepared for that yet.

You could literally just add more fans in parallel with the existing one and adjust R9 accordingly.

Guessing U3 determines how "on" the FET is and thus controls the fan speed?

Not a bad design at all.

[DragonTamer1]

5 hours ago, rhyseyness said:

You could literally just add more fans in parallel with the existing one and adjust R9 accordingly.

Guessing U3 determines how "on" the FET is and thus controls the fan speed?

Not a bad design at all.

The problem with adding more fans in parallel is that U3 measures their speed with their current usage. Unless all the fans are perfectly synced then it will give false readings and could possibly trigger a fault state. R9 would also continue to get outrageously small (into the miliohm range) and sine I don't have anything that small lying around I have no idea how accurate it would be. I was able to successfully duplicate the M1, Q1 and R8 portion of the circuit to increase it's output. Unfortunately sense feedback is still needed, I was unable to bypass this as I thought it wasn't necessary for a computer case fan that could be subject to interference from the user.

 

U3 creates a 30Hz signal that is sent to Q1. Based on the input from U2 it controls the duty cycle of the output to modify how long Q1 stays open.