12V/0.163A DC Brushless Fan speed control.

Thread Starter

ashutosh 123

Joined Feb 26, 2017
38
hi,

I need to design a control circuit for No-PWM fan which will be vary the speed of the fan base on supply voltage to the Fan.

Please help me with circuit
 

ArakelTheDragon

Joined Nov 18, 2016
1,362
I think scot did not see its a "non-pwm" fan control.

That is not so hard, you need a transistor on the output. But the understanding of how it works is hard at the start.

You can put the motor in the emitter and a resistor in the collector to limit the current. After that you need to control the base voltage and current with 2 pots.

Like this circuit:
https://www.google.de/url?sa=i&rct=...aw3oBbOTS-Ua3t0yr8-Q9mev&ust=1540273137378922
 

Thread Starter

ashutosh 123

Joined Feb 26, 2017
38
I think scot did not see its a "non-pwm" fan control.

That is not so hard, you need a transistor on the output. But the understanding of how it works is hard at the start.

You can put the motor in the emitter and a resistor in the collector to limit the current. After that you need to control the base voltage and current with 2 pots.

Like this circuit:
https://www.google.de/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwixudX0qpneAhUhsKQKHRIjBzUQjRx6BAgBEAU&url=https://electronics.stackexchange.com/questions/322668/why-do-we-still-use-bipolar-transistors-for-class-a-b-amplifiers&psig=AOvVaw3oBbOTS-Ua3t0yr8-Q9mev&ust=1540273137378922

Hi,

Is it possible that if vary voltage the rpm will automatically change,if i connect fan directly to 12V?
 

ScottWang

Joined Aug 23, 2012
7,397
I think scot did not see its a "non-pwm" fan control.
I have saw that, but what I can't make sure is that the TS doesn't want the PWM control or the fan can't use PWM control, and I also suggested the PWM control, because it can be insert the D(diode) and C(cap) between the 555 and NPN or NMOSFET to converts the pulse to voltage.
 

wayneh

Joined Sep 9, 2010
17,496
hi,

I need to design a control circuit for No-PWM fan which will be vary the speed of the fan base on supply voltage to the Fan.

Please help me with circuit
Just curious: If you want an analog control scheme, why did you post this under "Digital Circuit Design"?

That doesn't matter much, but what I'm really asking is, why do you want to avoid PWM? It's a very good choice, easy to implement, and works well.
 

Reloadron

Joined Jan 15, 2015
7,501
This is a data sheet for your fan. My read is:
Rated Voltage: 12 VDC
Rated Current: 163 mA / Maximum 188 mA
Rated Power Consumption: 1.96 Watts / Maximum 2.26 Watts
Operating Voltage Range: 4.5 to 13.8 VDC
Starting Voltage: 4.5 VDC

I need to design a control circuit for No-PWM fan which will be vary the speed of the fan base on supply voltage to the Fan.
With that in mind I would just place a pot in series with the fan. The fan needs a minimum of 4.5 VDC applied to start. You know your working voltage (supply voltage) and you know how much voltage you want to drop along with the max current so work out the numbers and get a potentiometer and place it in series with the fan and make sure the pot is rated for the power it will dissipate. That or just buy a cheap (inexpensive) fan speed controller as used in home computers.

Ron
 

ScottWang

Joined Aug 23, 2012
7,397
Just curious: If you want an analog control scheme, why did you post this under "Digital Circuit Design"?

That doesn't matter much, but what I'm really asking is, why do you want to avoid PWM? It's a very good choice, easy to implement, and works well.
I think probably the TS saw the Operating Voltage Range: 4.5 to 13.8 VDC, so he think that it can't use PWM to control, but he didn't know when use the PWM and the duty cycle is 50% then the average voltage only 6V and when the duty cycle is 37.5% then the average voltage is 4.5V.
 

Thread Starter

ashutosh 123

Joined Feb 26, 2017
38
i added the circuit.please anyone review it.can you please review and suggest me values for resistors and capacitors?

ash

IMG_20181024_215655_ashutosh 123.jpg
 
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Reloadron

Joined Jan 15, 2015
7,501
I need to design a control circuit for No-PWM fan which will be vary the speed of the fan base on supply voltage to the Fan.
What did you mean by No-PWM? What did you mean by:
vary the speed of the fan base on supply voltage
Your circuit uses a PWM signal. You can remove R1 and R2 unless you plan to use the Tach out signal from the fan in which case R1 can be 10K Ohm. Why is R4 in parallel with your N Channel MOSFET? Replace C1 with a 10K resistor Gate to Ground.If you want a tach out pull up make it 10K.

All you need to PWM a simple computer type fan is like the below:
PWM Fan.png

Diode D1 is just used as a flyback diode. The N Channel MOSFET is a Logic Level type and you could use a much lighter MOSFET as you have a low fan current.

Ron
 

Thread Starter

ashutosh 123

Joined Feb 26, 2017
38
Hi

I used R4 ,so that if I don't want to use own signal I will remove r3 and mount r4.so that fan will run with full capacity.
R1 I need in my circuit as tach pin is open drain configuration.thanks for the diode info. Can u help me with the resistor values?
 

Reloadron

Joined Jan 15, 2015
7,501
I want to believe the tach out on most fans is an open collector NPN and when I used it I just used a 10K resistor to +12 volts. Normally two pulses per revolution. Again, all you need for the fan is what I show in my drawing.

Ron
 
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