So I want to put a fan on my modem...

Nordic · Dec 18, 2013

... not because I need it, but because I want it.

The modem is a Motorola sb6121. I want to mount in externally, and it has an exact hole the size of an 80mm fan. What I need to know though is how to power the fan. I have read people have soldered the fan directly to the pcb, but I am not educated enough to know where this is. I also read others also used a more powerful psu cable.

Just so no one mentions it, the modem is mine, not the cable companies.

BazookaJoe · Dec 18, 2013

Well one far safer & simpler way to do this is to simply use an external variable power supply to power the fan that you can gently glue with hot glue to one side of the device - I see it has sort of a ventilated mesh on each side.

The main reason I would go this way first is because it is a lot easier - its a lot less risky, and should you ever want to sell the device you haven't altered its guts in any way and you can just pop the fan off again as hot glue holds well but can also be removed rather easily.

Beyond this a variable power supply is a lot easier to control - you really don't want the fan on full power all the time, too much airflow can be as bad as not enough - as over time it can pull dust and mess into the modem blocking it up and depending on your environment even land up filling that dust and gunk with humidity that can corrode the guts of the modem.

Anything like one of these AC/DC power supplies is fine - any size - even an old cellphone charger (usually 5v) will do just fine.

With a variable adapter you can drop the voltage as low as possible ( Many 12v 8cm fans can run on as little as 3v although a few may battle to start on less than 5v )- this will keep the fan QUIET and make sure its only just creating a gentle breeze through the device to help it cool rather than using its guts like a vacuum cleaner bag and packing the modem full of junk.

OR if you have an unused cellphone charger even better - almost all of these put out around 5v now which is usually more than enough to run a standard PC fan nice and slow and quiet.

Its not quite as convenient as running it all off one power supply but its all pretty much just going to sit in a corner somewhere anyway

However if you 100% want a self contained solution get me some better pictures of this :

The ratings on the power brick, and the back panel where the power plugs into the modem and i can help you from there.

We can even do a DIY variable fan speed control if you like.

pr0n Inspector · Dec 18, 2013

looks like that modem runs on 12v. you have to find a really slow fan or figure out a way to drop/control the voltage.

Personally I don't think modems and routers in general need active cooling. Put them closer to ground for cooler air if you want.

SaiZo · Dec 18, 2013

pr0n Inspector said:
looks like that modem runs on 12v. you have to find a really slow fan or figure out a way to drop/control the voltage.

Personally I don't think modems and routers in general need active cooling. Put them closer to ground for cooler air if you want.

Uhm, why does it need a "really slow fan"? Most fans either run 5v or 12v. Were you thinking of using a more silent fan, as the 5v types makes less noise? Or a discrete one inside the modem??
But otherwise, both my Motorola modem aswell as the Netgear modem used to run hot - but they did not take any damage from the heat.
Ofcourse the lifespan would be greater with active cooling, since heat is not a good friend directly.

Just a thought, why not also use a heatsink and adhesive thermal pad (or glue if there is any)?
Want to be able to turn the fan on/off? Get a small switch and solder it to the fan. And as BazookaJoe said - external power supply. That's a good option, I run my chassie fans on their own power source.

v12dock · Dec 18, 2013

Hot glue to the power input of the device, I have done this several times

rtwjunkie · Dec 18, 2013

Don't most modems have vents on the bottom? The solution I used was to take small rubber feet, like on a tower (even smaller diameter rubber washers will do), and glue to each of the four corners underneath. This raises it up, and with a ceiling fan that I have, enough air is circulated in the room that there is air movement underneath the router. I don't have exact temps, but the hand touch from before and consistently afterwards differs from almost hot to the touch on top to just alittle warm.

de.das.dude · Dec 18, 2013

get 50mm fans that are specifically made for this. ball bearing low sound ones will work great!

xvi · Dec 18, 2013

Was going to say that the power supplies for most modems are somewhere around the normal voltage for a fan. I wouldn't trust my word alone (read: wait for a second opinion), but I believe most DC 12v fans technically can operate up to ~24 volts without completely blowing up. I wouldn't trust one myself more than 15v without extensive testing, but it's an option if you find it's actually a 20v supply or something.

Nordic · Dec 18, 2013

pr0n Inspector said:
Personally I don't think modems and routers in general need active cooling. Put them closer to ground for cooler air if you want.

I want to put a fan on my modem not because I need it, but because I want it. I am not doing this because the modem runs warm, which does not bother me. I am doing for fun. I have this uber slow running 80mm fan that is useless to me for almost every application, but would work just fine for cooling a modem. I saw that someone put a fan on their modem once and I wanted to do that for fun. I do plan on putting a heatsink in there also, not because it needs it but for fun.

At bazooka, I don't want to have two powercables coming from the modem. I also am uninterested in on off capabilities. I will get a better picture of that power supply area today.

JunkBear · Dec 18, 2013

Make it simple. Look at the output power rate on the power supply of the modem. So take double the resistance and you will basically get 6volts. Here's the formula for that: 12V / Input Amps = Resistance in Ohms. Double that ohms and you get a resistance at electronic store rated 12V and that resistance. Solder a wire on the Positive of the power connector then the resistance with a wire going to a 12V fan then the negative side of the fan wired to the negative of the power plug on the modem inside. You will get a 12V fan turning at lower rpm because of the 6V.

Nordic · Dec 18, 2013

This fan is so slow I wouldn't want it going any slower.

JunkBear · Dec 18, 2013

You need a power supply fan from a cheap power supply. To see the speed of the fan at full just plug it on car battery or car battery charger at 12v .. if its fast and Noisy thats the one you use to lower at 6v.

Nordic · Dec 18, 2013

I have a specific fan I want to use because I already have it, and it is almost useless to me. Its 80mm which the modem just so happens to have a nice ventilation area 80x80mm.

Norton · Dec 18, 2013

You could scavenge a fan from a stock AMD cpu cooler and run it off of the 5v from a USB cable. I did a similar thing a while back when I pulled the fans out of a busted laptop cooling pad...

Nordic · Dec 18, 2013

So you guys are saying the fan in the picture I showed wont work?

pr0n Inspector · Dec 19, 2013

I'm pretty sure any 12v fan will work if noise is not an issue. 80mm fans draw very little current, especially yours since it is slow. Just don't put a Delta on it those things eat more power tha nyour modem!

xvi · Dec 19, 2013

james888 said:
So you guys are saying the fan in the picture I showed wont work?

Oh, it'll work just fine if you wire it in to the power adapter, but I'd plug the fan in to a computer first to make sure it's not going to make too much noise. It might require some soldering to get reliable. Might consider a resistor in-line just to bring the amperage (and noise) down.

Nordic · Dec 19, 2013

xvi said:
Oh, it'll work just fine if you wire it in to the power adapter, but I'd plug the fan in to a computer first to make sure it's not going to make too much noise. It might require some soldering to get reliable. Might consider a resistor in-line just to bring the amperage (and noise) down.

I know it is quiet. It is such a slow fan it has no use for cooling computer parts.

As soon as my camera's batteries are charged I will get photos of the power area.

micropage7 · Dec 19, 2013

why you dont put bigger heatsink on that, its easier
fan would attract more dust inside of it

Arjai · Dec 19, 2013

Just do it! Use a little duct tape and electrical tape. Be sure to do a few shots of Whisky, First. Then, go online and up your fire insurance, sit back and enjoy another Whisky while enjoying the small sparkly show!!

P.S. crack a window, the smoke smells bad.

segalaw19800 · Dec 19, 2013

why not use chip set heatsinks like

segalaw19800 · Dec 19, 2013

by the way my motorola modem is SB6121 and my fan is mounted on the side and wire to pcb it was e-z to wire thay way..... Dust is e-z to blow off from in side, out

Nordic · Dec 19, 2013

micropage7 said:
why you dont put bigger heatsink on that, its easier
fan would attract more dust inside of it

I will be doing that too. Not because I need it but because I want to.

Nordic · Dec 19, 2013

segalaw19800 said:
why not use chip set heatsinks like

I have some heatsinks like this. I have even stated I plan on using a heatsink several time snow.

segalaw19800 said:
by the way my motorola modem is SB6121 and my fan is mounted on the side and wire to pcb it was e-z to wire thay way..... Dust is e-z to blow off from in side, out

That is exactly how I plan on doing. I just need to know where to "wire it too." It looks like you can help.

segalaw19800 · Dec 19, 2013

Have fun

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So I want to put a fan on my modem...

Nordic

BazookaJoe

pr0n Inspector

SaiZo

v12dock

Block Caption of Rainey Street

rtwjunkie

PC Gaming Enthusiast

de.das.dude

Pro Indian Modder

xvi

Nordic

JunkBear

Nordic

JunkBear

Nordic

Norton

Moderator - Returning from the Darkness

Nordic

pr0n Inspector

xvi

Nordic

micropage7

Arjai

segalaw19800

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Nordic

Nordic

segalaw19800

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