need help with making a fan (electrical question) (1 Viewer)

[ryan_m]

I want to use a computer fan to cool my receiver. I have a 12v DC fan and an old power cord (from a lamp). What do I need to be able to plug the fan into the wall outlet? I'm assuming there is some part I can get at Radio Shack that will go between the fan and the cord?
Also, I have a Outlaw 1050 with a 12v trigger on the back that supposedly could power a fan. If I wanted to use that would I need the same setup as above (with a different cord of course)?
I'm currently just using a big fan sitting in front of my receiver to cool it. That's kind of annoying.
Thanks a lot,
Ryan

 

[Gordon Moore]

Ryan, most people have used a DC adaptor (AC input DC output), that way you can regulate the voltage of the fan (and the speed)...I guess you could get away without one but your fan will be spinning at top speed and might wind up being unnecessarily loud. You would have to cut the adaptor multi end and splice the wires together with the fan. The other advantage of going with an adaptor is that you can change the direction of the fan by using the polarity switch, however you can simply reverse the connection of the wires to acheive the same effect.

 

[Dan_D]

if you wire a 12V DC computer fan to a 110V AC circuit, that fan will be toast in seconds.
I once tried a similar thing. I measued a 36V source inside one of my old recievers that kept overheating and i wired 3 12V fans in series to it. Occording to Ohm's Law that would have given 12V to each fan. However i neglected the fact that fans are inductors not resistors they they fried right up

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[Bob McElfresh]

Ryan: please be careful.
For about $15 you can get a small 3" or 4" muffin fan that runs off of 120 volts AC instead of 12 volts DC.
If you want to stick with the 12 volt fan, go to radio shack and find one of those replacement power transformers. The ones with multiple tips and a switch to go from 3 volts - 12 volts. Buy the one that handles the most current. With this you can run the fan at slower speed by simply sending it 9 volts (to reduce the fan noise).
Do NOT try to drive a fan off of a 12 volt trigger. I dont believe this is designed to provide power. It is just a trigger.
Often times, a small clip-on fan sold at drug stores is the easiest, safest, quickest thing to get and attach. Put the small fan at the back of the rack and position it to blow across the top of the receiver, not directly into it (or you will also be injecting dust into the unit).

 

[ryan_m]

Bob,
Go to a store and buy a cheap fan already put together? That makes too much sense, what fun is that? My girlfriend was wondering why I didn't just do that too. ha
I did read somewhere that you could power a fan with the 12v trigger but who knows. I have another receiver that is powering a sub which has 2 outlets on the back so I was just going to plug the fan into that.
Thanks for the suggestions.
-Ryan

 

[Bob McElfresh]

Wireing your own interconnects is fine.
Playing with speaker & sub positions is fine.
Wiring up bass-shakers is fine.
I love playing arround with HT equipment and encourage you to do the same.
But it's hard for any of the above to kill you, or start a fire like 120 volts AC. This is why I urge you to buy a store-bought fan. Preferably with the "UL" symbol somewhere on the box.
(Note: I am an electrical engineer and I am confident in many of my skills. But when it comes to AC or power wiring, I hire an electrictian who does this stuff for a living.)

 

[John GB]

Just out of curiosity, what are you trying to cool? Most consumer grade receivers will run fine without any external cooling sources (provided you give them a little room to breath). I used to have to cool my system down because I mistakenly placed the receiver in the middle of the rack. The heat generated by the receiver affected the components sitting above it. This caused my VCR to malfunction. I used a RatShack muffin fan that runs on 120 VAC. plugged into the switched outlet on the receiver. It did make a bit of noise however. Once I wised up and moved my receiver to the top of the rack, all problems related to overheating went away. I no longer use an external cooling fan.
Good luck

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[patrick miller]

the fan will not work with the ac current. ac current alternates, so the fan would be switching directions constantly.

 

[ryan_m]

Bob I totally hear what you're saying. I will probably just end up doing what you're suggesting. One question though, if I did use an AC/DC converter (like suggested) the amount of power coming out of the converter (3-12Vs it looks like) isn't going to do much damage to me right? It looks like those converters are almost as expensive as a store bought fan. I am concerned that the fan will be too noisy though.
quote: Just out of curiosity, what are you trying to cool? [/quote]
I'm trying to keep my Outlaw 1050 cool. It gets very hot. I put a thermometer on top of it (one that would be used in a lizards cage or something) and it gets up to like 115-120 degrees and is very hot to the touch. The shelving system it's currently in isn't the best for it but I don't think it's THAT bad. It's open in the front/back and has about 3" of space on top and 1" on the sides. My room is like the hottest room in my apt though. I will be building a Flexy rack soon though and plan to give my receiver LOTS of space on that. I now just have an oscillating fan sitting in front of it which just clutters up my already very cluttered up room (I live in 2 bedroom apt and the one room is my ht/computer/bed room, so it's a bit crowded).
[Edited last by ryan_m on July 12, 2001 at 03:33 PM]

 

[John GB]

I'd consider contacting Outlaw to see if the 115-120 degrees is a problem for the unit. I bet not. You may just want to forget the fan to keep things nice and quiet.
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[Bob McElfresh]

Ryan: the little "battery eliminator" with selectable voltage is a very low-power device. One of the nice things is you can send 10/8 volts to the fan instead of 12 which will slow it down so you dont hear the noise.
Another option: find a good hardware store that might have a "dimmer" feature attached to a extension cord. Buy this and the small 120 v AC electric fan and use the "dimmer" to slow it down so you dont hear it.
And I have to tell you, 3" of space above your Outlaw is NOT enough room.
You can skip the fan if you take the Outlaw out of the rack and put it on top of your cabinent.

 

[Mike Bushroe]

I have recently had a similar problem with a yamaha receiver. Too little ventilation and the receiver went into thermal overload shut down when playing ID4 at too loud a level. So, I punched a few holes in the back and added a couple of 4 inch 120V AC muffin fans, plugged into the auxilairy power outlets on the back of the receiver.
The receiver is fine, nice and cool, but the noise is considerable. The package calimed 70 cubic feet per minute air flow (and they do generate a a good breeze), 11-13 watts, and 30 DB of noise. But they sound a lot louder than that. Even after I had pushed the equipment cabinet back up against the wall (with 32 inch TV still on top, back hurts

) and, my rat shack SPL says 55-60 DB. ANd the noise is VERY obviuos. It has cut the whole bottom end of my dynamic range. When the receiver starts up, there is a pause of about 10 seconds before the music sounds, and I can hear the fan spooling up like a jet engine turbine. And I only have 1 of the two fans powered up. The total cost per fan for fan, cover grill and plug in power cord was about $30.
So, i would suggest 'auditioning' fans before installing, and maybe before buying.
Mike