ok, first of all im a member on several moding forums and this one appears to be the best one thus far, im not a noob to modding or hardware but i am to electronics second of all i have 5 80mm fans in a string (each using the last ones molex connecter) and i want to use a fan controler for when i go to bed and have to leave the pc on to download something. my question is this : if i use a rheostat infront of the first fan to control the speed will it affect all the fans or just some? part 2 : will the rheostat be shorted out because its pulling alot of power? thanks, i look forward to hearing about this
If you wire it properly you should have no problems. And 5 fans should not cause any problem worries at all unless you are using something like a 100watt powersupply. Of all the fan buses I have built the only problems I have had was with the first 12v/off/7v I made. In that case I wired the switches and leds all in series instead of parallel so so the leds each got dimmer then the one before it and the 12v line indicator leds would not lite if any of the 7v indicator leds were on. Even with these led problems it didn't affect the power going to the fans at all, or at least not noticbly seeing as they all register at all most the same rpms. BTW that was with 6 80mm fans and the 3 leds per fan built into the fans (they were antec blues) powered off of one power line on one bus. I realize these are different buses but unless you mess up the circuit bad or get the wrong components 5 fans should be no problem. -Nesbit
is a home made rheobus easy to do? for someone who has no knowledge of electronics and only a cursory skill at soldering?
its easy enuf but i would have thought that 5 fans would be a lot of power on one rheostat and would probably burn it out but if u just use a switch it will probably be ok
Sorry delphia, I'm just jumping on your post. I want to pick nebit37 brain. I've got four antec blue leded fans, I'm going to run the led's of a seperate molex. I just want to know what pot I would need to run say 2 fans fans off a baybus and 4 fans off it. Not sure if i'm going to run 4 fans or 2 of 1 controller. I hope that is clear? I know a little but not enough. Well very little..........
1st note yes 5 fans on 1 rheostat would probally kill it, but not 5 fans distributed across the whole bus. 2nd Cyberbob I am a little unclear on your plans. I get what your saying about running the leds seperate from the fans but do you mean 2 fans per rheostat on a bus of X rheostats? If you can keep it to 1 fan per rheostat that is ideal but if one of them has an extra fan hooked to it it shouldn't kill it. A word of warning tho, if built improperly or overloaded a rheo-bus can kill your system so do your research well. For your first one I recommend you use Nox|Silicone's unfriable Rheobus . It is generally safe as far as not frying your whole system if you overload it. If you are underconfident in your electronic skills you should either buy one or make either an on/off bus or a 7v/12v bus before moving onto the rheo bus, electro bus or the PWM Fan Controller. Whichever one you decide to try out make sure that you test it using just a fan(s) and a powersupply in case something did go horribly wrong, but they are generally pretty safe as long as you take your time and carefully follow any of the plans you are using and ask for help if you get stuck. Also rheostats can be quite expensive, like £8 and up each. If you don't want to take chances and are trying to save money by doing it yourself you may want to buy one of the many kits/pre built rheo buses out there like this one. Hope this all helps! -Nesbit
To be specific, Multiple parallel fans will draw too much current through your rheostat. This will make it hot. Enough of that will make it fail (and then you got no fans, bad mojo). Agreed that voltage regulators are a big improvement in that regard. You get the current handling capability you want at a much lower cost. Our esttemed moderator has made a couple tweaks to the regulator-bus idea which are worthy of serious consideration. Dig it. There's also the transistor approach, which has some benefits, but is not protected against short-circuiting the output the way the regulators are. All in all, the regulator-bus is the best approach for you given all info available to me right now.
Thanks for the plugs, linear To get even more specific and hopefully answer cyberbob, check the maths for your fans; Say it's a 120mA fan - resistance is 12/.12 = 100R. Ideal rheostat is the same value, which will give a 6-12v range. Power needed is I*I*R = 1.44W. (R is the rheostat resistance, not the fan) Now with two fans parallelled, the effective resistance is 50R and the max current 240mA. If you stick with the 100R rheostat, you'll need a 5.76W unit, or changing to a more sensible 50R model, a 2.88W will be OK. At 4 fans, effective resistance 25R, max current 480mA. So a 100R rheostat would need to be 23W, a 50R 11.5W and the ideal 25R model 5.76W. These are conservative figures, and a 25R 5W rheostat would run 4 modest fans no problem, but you'll see that a "general-purpose" 50R or 100R rheostat needs to be high-wattage if you add extra fans to it.
Thanks for all your answers guys..... I think that has answered my question nicely.... All I have to do now is to put it into practice.......
