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### Topic: Variable 12 voltage remotely (Read 3718 times)previous topic - next topic

#### wvmarle

#15
##### Jan 11, 2019, 06:25 pm
sorry for don't provide the full detail.
It's not too late. You can still do so. We've only just had one page of talk about the wrong solution to the problem.

What is that power used for? You suggest it's for regulating a fan speed, correct?
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### TonyStarkC10

#16
##### Jan 11, 2019, 10:20 pm
It's not too late. You can still do so. We've only just had one page of talk about the wrong solution to the problem.

What is that power used for? You suggest it's for regulating a fan speed, correct?
yes it has Molex connector which is connected to pc PSU but before that, I'm gonna use boost/buck converter and whatever needed to adjust the voltage to the fan controller Molex input

#### outsider

#17
##### Jan 11, 2019, 10:48 pm
Reducing the voltage of a motor with a constant torque load by 50% will reduce the speed about 50%, but a fan is not constant torque, torque varies approximately with the square of speed, suggest testing effect of voltage variation to see what kind of voltage and current needed.

#### TonyStarkC10

#18
##### Jan 12, 2019, 12:06 am
Reducing the voltage of a motor with a constant torque load by 50% will reduce the speed about 50%, but a fan is not constant torque, torque varies approximately with the square of speed, suggest testing effect of voltage variation to see what kind of voltage and current needed.
Thank you, I have been tested it and at the highest speed, it needs about 10W (~0.9A @ 12V) and the fans start spinning at something about 2.5V.

#### wvmarle

#19
##### Jan 12, 2019, 06:31 am
A boost then a buck converter sounds like the wrong solution any day. Not only because there actually are boost/buck type converters which can output the same voltage as on their input, it's also because you would normally control the current through a device directly, not through trying to manipulate its voltage.

Many fans can be controlled just fine using PWM instead. Much easier. All you need is a MOSFET and two resistors. Very easy for an Arduino to produce such a signal.

Some computer fans actually have a speed control signal and have this speed control built in. Even easier. That speed control signal is usually PWM or similar kind of block wave, which again an Arduino can easily produce.

The problem still is that we're 18 posts in and finally at least we know you're trying to control the speed of a fan, but we still don't know exactly what fan (part number).

Indeed, sounds like this is yet another example of an XY problem...
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### GeronimoDK

#20
##### Jan 12, 2019, 01:47 pm
Ahhh, so you actually don't want adjustable voltage!? You just want two speed settings for your fans?

The easiest solution would still be using 1 MOSFET and using PWM on your Arduino!
You will not need any regulators at all, no linear no buck, no boost, nothing, just the MOSFET and your existing 12V supply!
You don't have to make it so that you can adjust it, you could just have two settings like 1 button for 100% and another button for 50%!

#### TonyStarkC10

#21
##### Jan 12, 2019, 05:19 pm
A boost then a buck converter sounds like the wrong solution any day. Not only because there actually are boost/buck type converters which can output the same voltage as on their input, it's also because you would normally control the current through a device directly, not through trying to manipulate its voltage.

Many fans can be controlled just fine using PWM instead. Much easier. All you need is a MOSFET and two resistors. Very easy for an Arduino to produce such a signal.

Some computer fans actually have a speed control signal and have this speed control built in. Even easier. That speed control signal is usually PWM or similar kind of block wave, which again an Arduino can easily produce.

The problem still is that we're 18 posts in and finally at least we know you're trying to control the speed of a fan, but we still don't know exactly what fan (part number).

Indeed, sounds like this is yet another example of an XY problem...
no just look at links below

https://imgur.com/gallery/wZnAXQg

Ahhh, so you actually don't want adjustable voltage!? You just want two speed settings for your fans?

The easiest solution would still be using 1 MOSFET and using PWM on your Arduino!
You will not need any regulators at all, no linear no buck, no boost, nothing, just the MOSFET and your existing 12V supply!
You don't have to make it so that you can adjust it, you could just have two settings like 1 button for 100% and another button for 50%!
it's exactly what controller do right now (50% - 100%) but I want something like (0% 10% 20% 30% and more until 100%)
take a look at the links below you will understand

https://imgur.com/gallery/wZnAXQg

#### wvmarle

#22
##### Jan 12, 2019, 06:08 pm
The MOSFET solution gives you 255 power levels using standard PWM. How you use those levels, and how many of them, is up to you.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### TonyStarkC10

#23
##### Jan 12, 2019, 07:27 pm
The MOSFET solution gives you 255 power levels using standard PWM. How you use those levels, and how many of them, is up to you.
WOW that's awesome. but how I can use it? can you provide me such a schematic for that

#### GeronimoDK

#24
##### Jan 12, 2019, 11:48 pm
https://www.arduino.cc/reference/en/language/functions/analog-io/analogwrite/

https://www.electronics-tutorials.ws/transistor/tran_7.html

It's not really that hard

#### TonyStarkC10

#25
##### Jan 13, 2019, 12:09 amLast Edit: Jan 13, 2019, 12:22 am by TonyStarkC10
Okay new how to use the push-button to increase and then decrease the speed of fans?
and what if we don't want to use an Arduino for that?

#### wvmarle

#26
##### Jan 13, 2019, 02:06 am
Easiest is two buttons. One to increase, one to decrease the speed.
Have a look at button tutorials on how to wire/read buttons. Have your buttons increase/decrease a variable.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### GeronimoDK

#27
##### Jan 14, 2019, 11:09 am
Why would you not want to use an Arduino?

If you don't want to use an Arduino but you do want to use push buttons, you need some other kind of controller, could be something else not-Arduino, like ESP32 or one of the gazillion of other controllers, or simply just a bare microcontroller, like an ATmega328. Maybe you could build some kind of digital control logic also, but it would probably require a whole bunch of IC's and a lot of time.

If you could live with a pot-meter instead of push buttons, maybe you could build some kind of analog variable PWM-generator, it shouldn't be too difficult.

#### Paul__B

#28
##### Jan 14, 2019, 11:22 am
or simply just a bare microcontroller, like an ATmega328.
Now in terms of building something to do a simple task like this, that makes no sense at all.  The smallest practical unit to implement a microprocessor control for something is an Arduino Pro Mini.  It has all the necessary support parts on it, directly wired for programming with a cheaply available USB to serial adaptor.

Yes, there are also some other modules using the ATtiny and such, but frankly, no cheaper than a Pro Mini from China.  However, trying to assemble the parts yourself from scratch - a futile exercise.

#### wvmarle

#29
##### Jan 14, 2019, 11:27 am
Not futile. Building ATtiny projects from scratch is fun, and totally doable.

That said, for OP's project I'd also go for a Pro Mini or maybe a Nano, solder wire up two buttons, PWM output through MOSFET (I still have some IRL540s that would do just great), a bit of programming, and in a few hours all set and done.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

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