Ken Jancef, Here is a writeup I did for controlling the fan using an Arduino and PWM

[G+_David Peach]

Ken Jancef, Here is a writeup I did for controlling the fan using an Arduino and PWM. Hopefully that will get you started. I was away from home and all my toys last week when we were talking about this, but after getting home yesterday I had to jump in and solve the problem even if just for myself.

 

Forgive any schematic errors, they didn't teach us this stuff in Bible college.

 

http://www.mythoughtspot.com/2017/06/20/controlling-a-fan-using-pwm-and-arduino/

http://www.mythoughtspot.com/2017/06/20/controlling-a-fan-using-pwm-and-arduino/

[G+_Shooter_FPV (Shooter_FP]

Thank you so much... this was very kind of you. I will most definitely check this out. I asked this before, but not sure if it was you that answered... the fan is 12V, but the Arduino is 9V. Will I be able to run the fan to its full power? Or should I read your post first? :)

[G+_David Peach]

Read the post first. I wrote it with the 12V issue in mind. I was actually running the fan in the video from 9V.

 

Your biggest concern is pushing too much amperage through the Arduino. You can power the Arduino from 12V and just use 1 power supply for everything, but having a separate power supply isn't that hard and eliminates the possibility of cooking the Arduino.

 

However, if someone wants to jump in and give us the safe numbers for powering the fan and Arduino (and the process for doing so) from a single 12V supply, I am all for it.

[G+_Shooter_FPV (Shooter_FP]

I did read it, albeit a little quick since it's getting late. It's starting to make sense, but I have no knowledge whatsoever about wiring electronics and reading schematics. Your post is making it clear. I'll read it in detail at work tomorrow. I know I will want to add the temp sensor, but this is an awesome start!!

[G+_David Peach]

The Instructable and Adafruit links will shed even more light on it all. When I did a similar project a few months ago (controlling 12V RGB LED strips with PWM), I finally started understanding transistors as switches.

 

Play with it and it might finally make sense.

[G+_Shooter_FPV (Shooter_FP]

David Peach I never thought about powering the fan and Arduino separately. That might work. Or at least I would think it would. Because the wire on the fan that matters is the PWM, correct?

[G+_David Peach]

PWM on the Arduino pin triggers the transistor to allow 12V to pass to the fan. So the Arduino is flipping the switch (transistor) on and off really fast (via PWM). That switch is controlling the 12V on and off really fast.

[G+_Shooter_FPV (Shooter_FP]

David Peach Ahh... yea, that makes sense....

[G+_Shooter_FPV (Shooter_FP]

David Peach I was going to try this project... would I still be able to power the fan separately, like your example?

 

electrosome.com - Temperature Controlled Fan using Arduino - Hobby Project

[G+_David Peach]

Yes you can, and must, power it separately in the linked project. That is what he is doing too. He shows a 9V battery powering his fan in the Fritzing sketch. In his video it looks like he is only using 7.2 V which is why he had to give it a little push to get it started.

 

The IC takes the place of my transistor, resistor, diode setup. But it is working in the same manner.

 

Good luck on this. It is nice that he has given a way to control based on temperature. It is your situation exactly.

[G+_Shooter_FPV (Shooter_FP]

Oh, ok. So I can feed the Arduino the power it needs (9V I think..), and feed 12V to the board for the fan..? Going to order the parts tomorrow. I'll let you know how I make out...

 

By the way... even though I like to have a wiring diagram to look at, I still like to learn about where things go and why... your post was the ONLY one I read that made me understand it. Much appreciated... :)

[G+_David Peach]

You're welcome. Glad it was helpful.

 

You can see in the video that he is using two power sources. He has the battery which is only powering the fan. The Arduino is plugged into USB and getting it's power that way. He doesn't show the Arduino's power source in the wiring diagram picture, but it is not using the 9V battery. Only the fan is getting power from the battery. His video makes that clearer.

 

As far as the power requirements for the Arduino Uno, it takes either power from USB (which is 5V), or it will take power through the barrel jack. The barrel jack can take anything from 5V up to 20V (I think), but ideally it is recommended 7V to 12V.

[G+_Shooter_FPV (Shooter_FP]

Thanks for the reply. Makes total sense. One of the "recommended" accessories to the Arduino on Amazon is a 9V power adapter, which I will get. And then relace his 9V battery with 12V for the fan. It's all making sense now... slowly... :)

[G+_Jason Marsh]

David Peach About your schematic.. is that an NPN or PNP transistor, and what's with D1. I'm accustomed to seeing diodes for draining induced current when de-energizing a relay, but on a low-current circuit like for your fan, I don't see the point. What am I missing?

 

Yes, one can infer transistor type from the schematic. For the n00bs, y'all. Everyone else can fend for themselves.

[G+_David Peach]

Jason Marsh, you are correct, I did not say whether it was an NPN or PNP. It is an NPN Darlington transistor. You can find out more about it by searching for "datasheet TIP122."

 

From the article about why to use the diode: "Between the collector and emitter we also insert a diode. This prevents the spinning of the fan (or DC motor) from pushing power back through the transistor and blowing up the Arduino. A DC motor (which a fan is) generates electricity when spinning but does not have outside power pushing it. So when the Arduino stops sending a signal to the fan the fan will spin down and in the process create a small DC voltage. In this case it is probably not enough to matter, but it is a good habit to put a diode in place to stop the newly created voltage from traveling backwards into the Arduino. As you probably know, a diode only allows the electricity to travel one direction. We want power to travel from the Arduino to the fan but not the other direction."

 

So, it is probably not necessary, but a nice habit when working with motors. (So I have been told. I am not a trained professional.)

[G+_Shooter_FPV (Shooter_FP]

David Peach So I got all the parts in for the build I linked to, and pretty effortlessly got it working, without the fan, only because it's not clear where the + or - goes, it just says "one terminal on the motor..." but fan, in my case. I would think it would matter, but maybe not???

[G+_David Peach]

If it is a two wire fan, then no, it probably doesn't matter. Like any DC motor, switching the positive and negative just makes it spin the other way.

 

You got those parts fast! Congratulations.

[G+_Shooter_FPV (Shooter_FP]

David Peach It's actually a 4-wire fan, but since it will be connected to all of this I wouldn't need the other 2 wires anyway.

 

Got the parts fast thanks to Amazon... lol... now I just need to figure out how I'm going to mount this to my enclosure...

[G+_David Peach]

Ken Jancef??, I think this will require some testing. Since your fan already has PWM brains built in, it may or may not work with this setup. To control yours with the built in PWM abilities, from what I have read, you will need a 25 kHz signal on the fan's PWM line. The Arduino does not provide that. You will have to use a library or write some special timing function to make it work.

 

What I would do is try your fan as if it were a two-wire fan. If using my circuit: hook your positive straight to the 12 V + power supply and the ground to the collector. If using the other circuit: connect the ground and + of your fan (you should be able to Google the pinout of your fan) into pins 3 and 6 of the IC. Should not matter which is which, but your fan may soon backwards. See it works.

 

Or, get a simpler fan. I have a dozen or two sitting in a junk box that I rip out of old computers people can't seem to stop giving me.

[G+_Shooter_FPV (Shooter_FP]

David Peach Ok... another question on this... so I got it all wired up and in my enclosure, but the problem I'm having is that when the temp gets to 30c, the fan is supposed to spin at 30%. But the fan doesn't start spinning. If I flick the blades with my finger it starts. It seems the fan may not be getting enough power? I'm feeding 12v to that breadboard. And the fan is a 4-wire fan... could that be the issue, as you said earlier there might be? The + is in Pin 6, the - is Pin 3. I tested it putting a soldering iron near the temp sensor. If I flip the + - it doesn't work at all...

[G+_David Peach]

Ken Jancef, try this: add spinning the fan up to 100% for 1 second and then let it drop down to 30%. That should get it started and then the PWM pulses after that should work as expected.

 

You may have to do a quick spin up for anything below a certain % to get it started. I would think anything above 75% should start OK on its own. You can test and see how low you can go to get it started or just add the 1 second (maybe less) of full power at the beginning of any percentage < 75 when starting from 0%.

 

(This is fun, me theorizing and having someone else put in the effort to see if my theories work.)

[G+_Shooter_FPV (Shooter_FP]

David Peach Its actually fun for me too... never coded before, especially with Arduino, so I'll find code that lets the fan spin up. Great suggestion...

[G+_Shooter_FPV (Shooter_FP]

In this example, "Enable" is Pin 5 on the Arduino, going into Pin 1 on the L293D chip

 

So here is a snippet of the code... could I do an addition of:

 

"analogWrite(Enable, 255)"

 

before the line "analogWrite(Enable, 77)" in the below example? Will the fan speed drop from the 255 (full power) to 77 (30% power)?

 

 

if(temp <30 ) { // If the temperature less than 30

analogWrite(Enable,0); // 0% PWM duty cycle

lcd.print("Fan OFF ");

delay(100);

}

else if(temp>=30 & temp<32) { // If the temperature is between 30 & 32

analogWrite(Enable, 77); // 30% of maximum duty cycle value (255).

lcd.print("Fan Speed: 30% ");

delay(100);

 

and on and on....

[G+_David Peach]

I am not an expert on this, but I would try (starting at your else if):

else if(temp>=30 & temp<32) {

analogWrite(Enable, 255);

delay(1000);

analogWrite(Enable, 77);

lcd.print("Fan Speed: 30% ");

delay(100);

 

I think that should spin your fan up to 100% for 1 second (you may not need that long) before it goes back to checking the temperature every 1/10 th of a second.

[G+_Shooter_FPV (Shooter_FP]

+David Peach That is SO funny... that is the exact code I put in... lol... but I am running a print right now, so I'll upload the code in the morning (the setup is at work). Does that mean I am ACTUALLY learning this?? Lol...