hey there,
just a very quick question here: Can i control a 12v PWM fan directly via the Arduinos 5v PWM output, or do I need to use a 12v signal?
I am talking about 12v, 4pin fans used in computers. There is quite a lot of projects online talking about using this, but I would like to get this information confirmed before turning my Arduino into blue smoke.
No. the Arduino only puts-out 5V at 40mA or less.
You need 12V plus a [u]driver circuit[/u] to "boost" the voltage and current.
The motor might run slowly at 5V but the Arduino can't put-out enough current to drive a motor so the voltage would drop, the Arduino would over-heat and it might burn-up!
1 Like
javamaster10000:
Can i control a 12v PWM fan directly via the Arduinos 5v PWM output
really? did you read what you're writing?
javamaster10000:
Can i control a 12v PWM fan directly via the Arduinos 5v PWM output, or do I need to use a 12v signal?
I am talking about 12v, 4pin fans used in computers.
There is a good chance that you can. To know for sure, you'd need a data sheet to your fan.
Your 4 pins are most likely: Positive supply, GND supply, PWM control, RPM sense.
If so, the control wire does not power the fan.
Wikipedia article on Computer fan control says:
A PWM-capable fan is usually connected to a 4-pin connector (pinout: Ground, +12 V, sense, control). The sense pin is used to relay the rotation speed of the fan and the control pin is an open-drain or open-collector output, which requires a pull-up to 5 V or 3.3 V in the fan.
(It also mentions a typical frequency of 25kHz. I don't know how critical that it, but it might be critical. This is not what you normally get from an analogWrite() on a PWM pin, so you may have to do some timer-1 magic.)
Try to find a data sheet if your fan has any markings on it.
You can use a logic Mosfet to driver your fan, but do not forget to install a protection diode in reverse as well (on the drain)
wolframore:
really? did you read what you're writing?
Not talking about supplying the fan with 5v but using a 5v pwm signal.
Jobi-Wan:
There is a good chance that you can. To know for sure, you'd need a data sheet to your fan.
Your 4 pins are most likely: Positive supply, GND supply, PWM control, RPM sense.
If so, the control wire does not power the fan.Wikipedia article on Computer fan control says: (It also mentions a typical frequency of 25kHz. I don't know how critical that it, but it might be critical. This is not what you normally get from an analogWrite() on a PWM pin, so you may have to do some timer-1 magic.)
Try to find a data sheet if your fan has any markings on it.
Thank you, jep, have read about the frequency thing too, but it seems to be quite simple to adjust the pwm frequency. I just need to find out which pin to use as they use diefferent base frequency's.
That’s why circuit drawing would be helpful. Half the time I’m guessing at what people are asking. Direct control implies a direct connection which wouldn’t work. If you want to control a switching device with the Arduino PWM you are controlling the power switch which in turn controls the motor.