I recently found a big 12 volt PC fan in someone’s garbage (along with a fifteen-year-old mouse) that looks like it has a PWM cable. There’s a black wire, a red wire, and a yellow wire. I hooked up the black and red wire to a 9v
battery and it spun very quickly, but didn’t blow much. I’ll show a picture later. Do I need a relay? How do I wire it to a relay? What can I use the fan for?
Thanks!
PS. The fan has mounting holes!
You connected a standard 9-Volt Battery?? The amount of Current needed to run the fan at its full capacity was most likely not enough.
You would need a 12 Volt Source and either a Relay or a Combination of two of Quazar’s Circuits,
How to drive a small DC load via Digital Out and Secondary Motor Circuit.
What is the end result that you want to achieve with the 12 Volt PC fan??
Its not PWM, the third yellow cable just feeds speed information to the motherboard inside the computer.
Most of these fans barely pull 1 amp so the battery is not the problem, they don’t really push much air. They do require 12 volts to work well, but don’t use anymore they like releasing magic smoke.
Oh by the way you can pick these fans up for dirt cheap on www.newegg.com. There are new ones that are PWM controlled, they have 4 wires (one for PWM and other for speed).
Thanks! I’ll try Quazar’s circuit. I just used a 9v battery to test the fan. Here’s some pics. The fan makes a decent amount of air with a 9v.
I had a thread on this a while back. You could probably just hook it up to a motor controller if you want to be able to control the speed, but otherwise just give it power. Also, I happen to have that exact same fan sitting here next to me, it’s from a Win98 Gateway (teh suck!) You can run them directly through a motor port with out any major power loss.
You’re right, it doesn’t push much air, only around the edges.
The Fan’s requirements should be located in the center of the Blades. You might find the Current requirements here as well as the Voltage requirements.
I just mounted it to The Flexx to cool the battery.(possibly batteries because I want more battery life so the Flexx can go on long missions) I made it so you can manually turn it on and off. I’m just using a 9v battery. It works geat!:DYAY!!!
I read your thread and that’s where I got the idea to put the fan over the batteries. Thanks!
with all the robots i have made the batteries never seemed to gain enough heat that i need a fan…how many motors do you have running at the same time?
My idea was to have The Flexx AIR run for a long time, so I thought that the batteries might become hot. I might use to parralel batteries to make the robot run for a long time, plus I’m getting a vexplorer receiver which will run on 6 motors, plus the microcontroller (I don’t think it will heat up very much).
I’ve had my motors get hot, but no batteries. the fans draw very little current though, so no huge load from them. These LEDs make good headlights and also draw very little power
The fan is also for looks too.
I have found a use for it. It’s really there just in case something gets hot, but it’s good to use when my microcontroller shorts. (I found out why it shorts. It’s because I wired the vexplorer cam badly)
what do you mean? how did you wire it? and is the vexplorer cam really worth the $70 USD?
I’s worth it, my problem was just that I made an arm for my robot and it bent the prongs. when I tried to bend them back, they broke off. I fixed it, but I didn’t have electrical tape, so it shorts every once in a while.
dude i have like 20 rolls of electrical tape…and let’s see, about 300 feet of 20 gauge wire…tons of other stuff… and all because my dad’s an industrial engineer. resourceful, huh?
I would head down to the local Radio Shack and get some Heat Shrink Tubing and maybe Electrical Tape (or Electrical Tape from Lowe’s or Home Depot). re: Radio Shack Heat Shrink Tubing.
I had the benefit of growing up with a Grandfather who was an Industrial Electrician, an Uncle who is an Electrical Engineer and a Generally Mechanically Inclined and Problem Solving family. I learned how to Solder at 6 or 7 years old. 
Used Electrician’s Tape before that, and though that Heat Shrink Tubing was the greatest thing, when I discovered it in 1987.
I’ve already fixed it. Thanks for showing me the heat shrink tubing! I might find it helpful some time.