A simple circuit to test PWM fans

[Spork Schivago]

Hello,

I'm looking to build a simple circuit that I can use to test fans that use Pulse Width Modulation. I currently have a three wired fan and if I provide 12V to it, it just spins for a second and then stops. I'm pretty certain the fan is good. I'd ultimately like to have something where I can easily test 3 and 4 wired fans. Does anyone have any schematics for something that would allow me to do this? I just want to be able to use something like a pot to change the speed of the fan. I have a variable power supply now so I can just set it to whatever voltage the fan takes and hook it to the wire.

[stj]

Re: A simple circuit to test PWM fans

you can probably find circuits based on a 555 timer chip.
or use a microcontroller.

[Spork Schivago]

Re: A simple circuit to test PWM fans

you can probably find circuits based on a 555 timer chip.
or use a microcontroller.

I like the 555 timer idea. I've never used a microcontroller before. I'm not against using one, I just have no idea how they work and I know nothing about them except that they're in a lot of different things. I saw some simple circuits using a 555 but it said stuff like it can only do 10% duty cycle and 90%.

[stj]

Re: A simple circuit to test PWM fans

isnt 10-90% enough for testing?

[Spork Schivago]

Re: A simple circuit to test PWM fans

My understanding wasn't 10% - 90%. It was 10% or 90%. Maybe I misunderstood it. I will try to find the schematics again for it. It was really poorly written. The person was 15 years old they said and the schematics didn't match the breadboard. For example, the breadboard had a cap but the schematics didn't. Some people some how got it work just fine, other people said it burned out a 555 timer. I was hoping for something better. If it can do 10% through 90%, that's more than fine. I mean, I guess 10% or 90% would be fine for testing too. I just thought it'd be nice to be able to adjust the speed to whatever via a pot or something.

[budm]

Re: A simple circuit to test PWM fans

http://www.dprg.org/tutorials/2005-11a/
But the fan you are trying to drive has the PWM control pin or any spec of the fan you are trying tot drive?

[Spork Schivago]

Re: A simple circuit to test PWM fans

Right now, the fan I am trying to drive is a 3-wire Nidec G10C12MS1AH-56J14 12VDC 1.38A fan, however, I'd like to make something that I could use to test various 3 and possibly even 4-wire fans in the feature, just not this fan.

[budm]

Re: A simple circuit to test PWM fans

NIDEC simple PWM control.

http://www.nidec.net/apps.htm
http://www.overclockers.com/pwm-fan-controller/

[sam_sam_sam]

Re: A simple circuit to test PWM fans

NIDEC simple PWM control.

http://www.nidec.net/apps.htm
http://www.overclockers.com/pwm-fan-controller/

Thank you for posting that link I have need a pwm controller using a 556 timer IC chip

[Spork Schivago]

Re: A simple circuit to test PWM fans

Are these schematics good for my fan? The fan I'm currently interested in testing requires 12V it says...these schematics make it look like it only provides 5V.

[budm]

Re: A simple circuit to test PWM fans

The PWM Controll pin requires 5V PWM signal, the Power Voltage for the fan to spin is 12Vdc, do not get confused between the Control signal (low current) circuit and the Power Voltage for the Fan drive circuit (high current).
You need to look up the fan spec to find out what the electrical requirements are.

[tom66]

Re: A simple circuit to test PWM fans

Note 4 wire fans use a fast PWM signal @ 25kHz. Slow PWM fans, ones controlled by switching the 12V supply, work at a much lower frequency, usually less than 100Hz.

The reason for moving to the high PWM frequency is the motor driver on the fan can control the current modulation more precisely for a specific speed. Whereas low frequency modulation usually results in the fan accelerating and slowing down rapidly at the PWM frequency, causing increased noise.

[Spork Schivago]

Re: A simple circuit to test PWM fans

Thanks guys! I would of built this buy now but I needed to earn some money so I've been busy working on other stuff. I'm all caught up for a bit now so I think maybe tomorrow or the next I'll start working on building this and learning more about creating my own hardware. Just need to take a little break first.

[Spork Schivago]

Re: A simple circuit to test PWM fans

Note 4 wire fans use a fast PWM signal @ 25kHz. Slow PWM fans, ones controlled by switching the 12V supply, work at a much lower frequency, usually less than 100Hz.

The reason for moving to the high PWM frequency is the motor driver on the fan can control the current modulation more precisely for a specific speed. Whereas low frequency modulation usually results in the fan accelerating and slowing down rapidly at the PWM frequency, causing increased noise.

I know it's been awhile since I last visited this topic but I had a question. The schematics Budm posted seem to use the fast PWM signal you talked about here Tom66, roughly 25KHz. Would I still be able to use this with the slower PWM fans? There wouldn't be any trouble, right? It'd just run at full speed, right?