Tempesta Posted March 28, 2005 Posted March 28, 2005 I did a search and found a few older topics about reversing polarity to case fans. Here's my situation and why I want to do this. I have a Tt Tsunami Dream case. I have a Sunon 92mm side intake fan, a 120mm blue LED Tt smart fan that's setup as rear exhaust, and a 120mm Aspire red LED front intake fan. I made some case and fan cage mods to maximize airflow, and I achieve 32C idle temps and ~42C load. The way the front of this case is designed, the front fan doesn't really do too much but provide red light for the case. It's quite noisy, mostly due to the restrictions in trying to pull in air. So I came across a new Cooler Master red LED 120mm fan. Super-bright LEDs, low fan RPM, and low noise. Bought one and plugged it up outside the case. Looks great (and the LEDs really are bright), but I noticed a problem. The LEDs are 'facing' one way.... you really have to mount the fan in one direction to get the maximum amount of light. Mounting the fan like that would mean that it turns this fan into an exhaust fan, not an intake. So I thought about reversing the positive and negative to the fan motor so it will reverse the fan rotation. I fly model airplanes and we run DC motors backwards all the time when they are attached to a gearbox. The fans are obviously DC but I saw several people state that they have a diode and will not run backwards with reverse polarity. My other concern is, will the LEDs light up if the polarity is reversed? Or are LEDs not polarity-specific? Or will they burn up? Should I just mount the fan as an exhaust and be done with it, since it's not doing much anyway? Thanks, as always, for the help! Share this post Link to post Share on other sites More sharing options...
Uber Posted March 28, 2005 Posted March 28, 2005 In theory the fan will spin backwards, but the LEDS will nto light up as they are a type of diode (Light Emitting Diode) they are polarity specific. might be worth a try though, depends how the fan is designed, you might be abel to get creative with a soldering iron and solder leads onto the LEDs, for another power source. Share this post Link to post Share on other sites More sharing options...
Varry Posted March 28, 2005 Posted March 28, 2005 also the fins on the fan's rotor are oriented in a certain way to maximize airmovement. Flying RC planes, you should know how sensitive fin orientation is. Making the fan spin backwards will result in almost no airmovement whatsoever Share this post Link to post Share on other sites More sharing options...
slayer2cool Posted March 28, 2005 Posted March 28, 2005 but the LEDS will nto light up as they are a type of diode (Light Emitting Diode) agreed.. Diode only allow for electrical current to flow in 1 direction only... so if it can flow from left to right, it cant flow from right to left.. soo yeah most probably it wont work Share this post Link to post Share on other sites More sharing options...
Varry Posted March 28, 2005 Posted March 28, 2005 as for the leds, once you reversed polarity on the fan, you could re-reverse the polarity of the leds through altering the wiring on the fan itself... of course you still won't have could airflow because of what i mentioned before Share this post Link to post Share on other sites More sharing options...
Tempesta Posted March 28, 2005 Posted March 28, 2005 also the fins on the fan's rotor are oriented in a certain way to maximize airmovement. Flying RC planes, you should know how sensitive fin orientation is. Making the fan spin backwards will result in almost no airmovement whatsoever 451866[/snapback] Yeah, I know that the fan blades are curved and oriented to provide maximum airflow, unlike the paddles of a ceiling fan, for example. I'm not too worried about the airflow since I don't think the existing fan does much of anything anyway. I've helped plane newbies with a poorly-flying plane to find out the prop is mounted backwards. Thanks for the info about the LEDs; I have no electrical experience with them so I didn't know if they were polarity-specific or not. I figured they were since they are DC but I wanted to double-check. That's a whole lot of soldering.... it's probably just easier to mount that fan as an exhaust rather than an intake. I'll check my temps and see if it makes a difference or not. That front fan was blowing across my Raptor but I guess it doesn't really get that hot after all. Thanks for the help as always! Share this post Link to post Share on other sites More sharing options...
exeter_acres Posted March 28, 2005 Posted March 28, 2005 off topic... What kind of planes?? I fly Glow and electric ...3Dfoamy style... Zagi flying wing with Brushless. etc. etc.. I think the issue with the fan would be the LED, and YEs, they are polarity specific... The fan would be OK, (I reverse brushed and brushless for airplanes too) but the LED would be the problem...unless as mentioned, you unsolder the wire/motor connectors and then resoldered them.... Share this post Link to post Share on other sites More sharing options...
Tempesta Posted March 28, 2005 Posted March 28, 2005 Sweet! A fellow flyer! I fly glow and electric. At last count, including my combat plane and an indoor electric chopper, I have 14. They range from 80" wingspan Big Boy to my 60.5" Ultimate Bipe to my Funny Park foamie. I have a Freedom 3D with a Mega brushless motor (my only one, as the others are all brushed) and that's my 'biggest' electric at 48" span. I think the ESC can tell the BL motors to run backwards, but I'm not sure, as the BL motors are essentially modified AC motors. All the brushed motors in my small foamies are neutrally timed, so they run just as well backwards as they do forwards. But anyways, yes, I have two expensive hobbies... computers and R/C planes. I'm looking at the fan now and that's a whole lot of small wires to be re-soldering. Don't know if it's going to be worth all that trouble. Share this post Link to post Share on other sites More sharing options...
CrackHead Posted March 30, 2005 Posted March 30, 2005 (edited) Off Topic but I use to go buy the starter flying airplane kits and then after becoming bored with them me and my friends would strap them with a small amount of black powder and watch them explode in mid flight...hella cool Edited March 30, 2005 by CrackHead Share this post Link to post Share on other sites More sharing options...
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