Hello everyone,
I have a 12V/0.22A cooler and I am guessing if I can power it through my arduino 5v pin. I believe that if I do so, the cooler will only spin slower than if I power it with a 12v external power source.
Is it right?
Thank you
If by "cooler" you mean a fan, then yes.
// Per.
Yes! Sorry
It is really a fan.
Just one more thing, the fan has three wires: black,yellow and red.
I am thinking about connecting them this way:
red wire - power pin - 5v arduino
black wire - gnd arduino
yellow wire - control pin - digital 7 arduino
Any suggestions?
Thank you very much
The three wire fans have no control pin. It's a tacho pin from which you can tell the speed, not control it!
Om 5V the fan will not turn hard at all. If you want more speed you need 12V. And if you want to control it as well you need a transistor.
Btw, I would not power the fan from the Arduino 5V if the Arduino isn't USB power. If you power the Arduino from 9V or 12V you load the voltage regulator pretty hard.
What is it that you're trying to achieve? do you just want the fan to spin or do you want to control it's speed or you want to activate it using arduino?
How are you planning to power your arduino? with USB or 12v adapter?
btw have you tried powering the fan with 5v? did it work?
septillion:
It's a tacho pin from which you can tell the speed, not control it!
Yepp
It is a simple project for school.
I am using a temperature sensor (LM35) to monitor the temperature and if it is higher than 30 degrees celsius I want to turn on the fan.
The problem is that i only have a 12v fan and no external power source, that is why I asked here.
Speed control is irrelevant, I only want to turn it on and off.
I am thinking about using a relay shield maybe
I am powering my arduino via USB
I have just powered the fan with the 5v from the arduino and it spins well, with a low but satisfatory speed
Thank you
arthuki:
I have just powered the fan with the 5v from the arduino and it spins well, with a low but satisfatory speed
Thank you
So the problem is solved, right?
arthuki:
Speed control is irrelevant, I only want to turn it on and off.
Those two statements are contradictory... If you want to turn it on/off you control the speed. You only have two speeds but you do control the speed 
But if 5V works for the application just add a transistor and a resistor to the mix and you're done. On the BJT side a BC547 (if its under 100mA, measure!) or a S8050 or any other NPN you can get your hand on. Or a n channel logic mosfet. Will switch with less loss but are more expensive.
Noobian:
So the problem is solved, right?
Unfortunatelly it is not.
I now know I can power the fan through the arduino 5v pin but I need to control when the fan is turned on and off. In my project, when the temperature is higher than 30 degrees celsius the fan is turned on, but I do not how to do this. I am studying and searching but I'm a bit lost with all this information.
On which part are you lost? The hardware? Tried this?
Is there a way for me to use the fan without a transistor?
Please understand that I live in a small town and eletronic componentes are really hard to get.
Thank You
Basically, no. Even if you want a relay to control the fan you need a transistor to drive the relay. The Arduino can't supply the current needed to drive a fan from its IO. If you buy one of those Arduino relay modules it already has a transistor on it. But if you can buy a relay module you can differently buy a transistor. It doesn't really matter which (as long as it's big enough for the current and voltage) so it's a really basic component.
arthuki:
but I need to control when the fan is turned on and off. In my project, when the temperature is higher than 30 degrees celsius the fan is turned on, but I do not how to do this.
So you need a circuit or you need the code? or both?
Note: You can salvage transistors from old electronic junk. and when I say old I mean "old", because the new ones use SMD transistors which are a bit tricky for beginners.
You mentioned a relay shield, you could switch the 5 volts from Arduino with that.
If you have one, could you post a link or picture?
My relay shield is this one:
http://arduino.computer-parts-store.com/Sun_Founder_2_Channel_5V_Relay_Shield.html
I have tried using the relay shield in this way:
Red wire of the fan into relay shield.
Relay shield into arduino 5v pin.
Black wire of the fan into arduino GND.
Left the yellow wire of the fan untouched.
With this configuration, The fan needed a little push to star spining, like it didn't have the strength to spin by its own.
That's not all the connections....
Vcc to arduino 5V
GND to Arduino 5V
Fan black to Arduino 5V
Fan red to NO contact of relay
Common contact of relay to Arduino 5V
And yeah, it might need a push. 5V is a but low for a 12V fan and now you have to power the relay as well. If you power it from a PC that can give you a significant voltage drop. Measure the 5V when the relay/fan is off and when it's on and see.
arthuki:
With this configuration, The fan needed a little push to star spining, like it didn't have the strength to spin by its own.
Because it's not getting enough current. The fans stall current is much higher than it's operating current, so it's needs more current to start.
It finally worked! I was so stupid no to consider the voltage drop over the relay shield. I got a 9V/1A external power source and powered the fan through it and used the relay shield to control the fan's turning on and off.
Thank you guys for all the help.
I've learned a lot in this topic
arthuki:
I was so stupid no to consider the voltage drop over the relay shield.
No you're not... The relay shield will have NO noticeable voltage drop at all...
Problem is, the relay also uses power causing the voltage on the whole Arduino to drop 