pwm fan

[Neongt]

so i found this board from coralux it does 4 fans by pwm is there any way to get 2 other pwm from the mega so we can control the fan speed ? i know it works off the led pwm i just need all of them for my lights thanks derek

[Rob F]

I'm actually waiting for a new board similar to that one, selling it for the same price. I made one 5cm x 5cm, it'll dim anything 12v DC using a 5v PWM pin. I made it for those LED strip lights, but it'll work with fans, pumps, things like that. It has 4 channels and I've marked it good for 6amps per channel but technically the components are good for 15+ amps per channel. The traces are the weak point. So the nice thing is it should run cool and put out no heat. It doesn't have power on board but I'll probably make a smaller one like this with on board power.

To answer your question there are lots of PWM pins available but you would need to add the code to control them. I'm quite busy with this update and other things so it'll be a while before I can do it. You're the only person to use up all 16 channels, looking forward to seeing how you set them up.

With the new update you'll be able to turn fans on/off via AC outlets using any of the temperature probes expect the air temp.

[Neongt]

i am working hard on this long weekend i have some pictures to load on my build but i am so close i can taste it if its not done this week end it will be in the next few days for sure have all the peaces

[fietsenrex]

how is the PWM mapped out? since the mega only has 13 PWM ports nut robo-tank offers 16..
I'm currently in the process of getting my fans to respond to PWM..
I use a TIP120 to control 6 fans on 24V (2x3 12v fans), they respond but the TIP120 makes a terrible humm..
I've set the PWM frequency to 400Hz in order to get my LDD's to stop humming.

do you have any idea how to get is sorted?
can I set 1 PWM pin to something like 20KHz so it isn't audible any more?

[Rob F]

The controller uses a separate IC for the LED's, not the PWM pins from the Arduino. You can't change the frequency for each channel, only for all. I have mine set at 1600Hz using LDD's and no hum. The new hardware has two IRFZ44N MOSFETS onboard, they don't squeal either. I just connected some LED strip lights again to verify. Maybe its just a bad TIP120, do you have another one to try? I'm sure I used some TIP120 in the past without a problem.

[fietsenrex]

Well that sucks...
My PWM is set to 400 in order to silene the humming of my LDD's

I'll see if I can get a hold on a second tip120

[Rob F]

Are you ok if the fans turned on/off using light temperature? If so what temps would you want it on/off? I could write a simple function you can add to the mega so you can use a pin on the arduino and change the frequency to what works. You wouldn't be able to access settings from display it would just work, to change on/off temps you would do it in the function.

[fietsenrex]

Well, over at tpt O2surplus suggested a arduino nano which boosts the frequency outside the hearing spectrum.
In that way I still can use the lighting schedule and keep the fans at a certain speed to keep the heatsink warmer than the water.
So a set point which is in the software isn't 100% what I'm looking for

[Rob F]

Hopefully you get it, let me know what you did if it works.

[fietsenrex]

got the nano in yesterday and programmed it
it works like a charm and responds properly to the different settings.

[Rob F]

Great, now you can keep things cool and quiet. :)

[fietsenrex]

Yup, pretty happy with that :)
Is one of the 5v spare pins powerfull enough to run the arduino nano?

[Rob F]

Yeah the spare 5v pins are good for at least 1 amp.

[fietsenrex]

Great, thanks

[rott]

fietsenrex can you post a link to the information other people might like to do the same thing you did. It sounds really cool :)

[fietsenrex]

http://www.plantedtank.net/#/topics/1042...&_k=umm167

Hope this works, but the thread sums up all my problems that I had with the lighting
On page 5 and 6 in the mobile view you can read about the fans