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Author Topic: Slow Increase Fan startup (Fade in?)  (Read 7642 times)

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Ceyarrecks

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Slow Increase Fan startup (Fade in?)
« on: April 18, 2011, 06:37:41 AM »
Good evening PCBHF;

I have an idea I want to implement in a new system I will be putting together soon that will have many 120mm fans.
my personal expertise in electronics is everything just short of ICs.

I have already looked through a few of the projects and circuits displayed here, and am not quite sure how one would adapt them for my idea. I would hope I may receive the guidance on how to construct a circuit to perform in the way I expect.

my idea is on the lines of "fade-in" dimmers but for the higher voltage (12v DC) of CPU fans.
yet I would want this:
1. be self-contained and fade-in automatically.
2. (this i think will be harder to implement) have a delay set to where fan1 spins up to maximum, then fan2 would begin its spin up, once reaching maximum rpm, fan3 would start, etc, etc.

where need I start in order to begin constructing a circuit that can handle up to 4 fans (or more)

Thank you kindly for the input and guidance.

CAH
_

kam

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Re: Slow Increase Fan startup (Fade in?)
« Reply #1 on: April 18, 2011, 08:32:32 AM »
i think i get the feel of your idea.  8) Yes i do! For i have already 4 120mm fans for my PC and i had once something similar, but i doped it. Anyway, in case that you do not want to use a microcontroller, which would make your life extremely simple. First you need something to perform a fade-in. You ca do it either with PWM, or with a linear circuit. PWM would be too complicated for this, and taking into account that the fans will eventually run at full rpm, a PWM circuit would be overkill. PWM over linear circuit has great advantages only if the fan runs at slower rpm than maximum. Therefore, i suggest you avoid this.

So, you will use a very very simple and basic linear circuit, like this:
Linear fan controller

Then, you need to change the resistor net R1-R2-R3 and the capacitor C1 with something that creates a linear voltage ramp from 0 volts to maximum 12 volts. The slower the ramp increases, the slower the fan will reach maximum rpm. You can make a ramp if you follow the same guidelines with this:
LED Fade In-Fade Out dimmer

You can use circuit #1, but it will have a great delay to start the fan. The problem is that the fan will start rotating from 7 volts and above. But circuit #1 will make a ramp from 0 to 12. Circuit 2 on the other hand will be better, because it creates a ramp from a pre-defined voltage level which is set through potentiometer R2. Moreover circuit #2 is simpler to adjust the fade in delay and fade out delay.

You will also use the BC327 as explained in last paragraph ("Need more current?") and there you have your fade in fan controller.

And then, you need something to check the rpm of the first fan, and when the fan goes to full rpm, the second will start and so on. I have some issues for this.  If for example fan 1 fails, then what? No other fan will start?
Anyway, there is a very simple solution for this.

PC Fan Failure Alarm
This circuit utilizes the yellow wire of a PC fan. When the rpm of the fan goes above a threshold level, then it changes the state of a relay. So, you will connect the output of the relay from the first fan,to the power supply of the circuit for the second fan and so on.

Ceyarrecks

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Re: Slow Increase Fan startup (Fade in?)
« Reply #2 on: April 18, 2011, 22:15:43 PM »
Kam:

thank you kindly for the direction and encouragement! ;D

I will begin collecting parts immediately,...

I just hope my limited IC knowledge will not be a, hmm, limiting factor. ???


Ceyarrecks

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Re: Slow Increase Fan startup (Fade in?)
« Reply #3 on: April 18, 2011, 22:44:24 PM »
uuumm,.. Kam,...

how would my life become more simple were I to use an IC?


kam

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Re: Slow Increase Fan startup (Fade in?)
« Reply #4 on: April 19, 2011, 08:05:56 AM »
a microcontroller, not any IC. With a microcontroller the whole circuit would be limited to... the microcontroller.... And of course a couple more parts like capacitors and resistors. With the microcontroller you can do the job with software and control the fans (4-wire fans) with PWM

Ceyarrecks

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Re: Slow Increase Fan startup (Fade in?)
« Reply #5 on: April 22, 2011, 22:54:22 PM »
Indeed, that does sound easier per se.
less pieces anyhow.

so now an obvious question from my point of view, while your statement I am sure makes perfect sense with your experience, where need I start to be able to construct this project intelligibly? Either by the micro-controller, or the pieced-together method?

While, yes, it would be easier to ask: “how to,...” and have all the answers provided, I would prefer to learn the process and such,… just I do not know what I do not know,... so where do I start?

Thank you in advance.

CAH

_pike

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Re: Slow Increase Fan startup (Fade in?)
« Reply #6 on: April 23, 2011, 00:39:34 AM »
If your intentions are ment to be the construction of this particular project,then you should avoid mcu....If you like and want to learn about programming mcu's, then you can start by a book provided by kam here...  http://pcbheaven.com/picpages/
VERY USEFUL!!!

kam

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Re: Slow Increase Fan startup (Fade in?)
« Reply #7 on: April 23, 2011, 13:07:56 PM »
IMO you should go with the analog design. MCUs are impressive and powerful, but analog are the ultimate solution -when possible-

Ceyarrecks

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Re: Slow Increase Fan startup (Fade in?)
« Reply #8 on: April 24, 2011, 22:37:36 PM »
Thank you for the inputs.

I can basically understand each of the individual circuit designs to be able to construct them.
so I can agree with the analog solutions, not ready for programming yet, heh.

and yes, I really do want this to be the crowning of the new system I will be building.

what I lack is the understanding of how to meld each of the circuits together to allow for combined functionality:

the stepped fade in circuit (though I would take an all-together solution if easier), and the fan fail alarm.

also, how do I automate the fade in? as I just want a fade in, no fade outs, and would prefer to have the circuit fade in on its own, as opposed to using a potentiometer (as noted in the circuit)

thank you kindly again for the guildance.

CAH

Ceyarrecks

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Re: Slow Increase Fan startup (Fade in?)
« Reply #9 on: April 29, 2011, 22:36:48 PM »
As I lack complete understanding beyond the basics, could someone verify the picture schematic attached as being correct in combining each of the functions desired...

Thank you

CAH

kam

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Re: Slow Increase Fan startup (Fade in?)
« Reply #10 on: April 30, 2011, 19:47:04 PM »
this is exactly what i would design myself. You can test it on a breadboard. Post the results so we know ;)

Ceyarrecks

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Re: Slow Increase Fan startup (Fade in?)
« Reply #11 on: April 30, 2011, 21:55:24 PM »
in regards to the two transistors, in perusing mouser.com's extensive inventory, it seems that BC548 from the LED Dimmer circuit can not dissipate much power, the power requirements of up to four (4) CPU fans would draw more current than the 548 can handle.
would SS8050 be a higher power transistor in this case?
(http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/SS8050CBU/?qs=sGAEpiMZZMvTzqKFuy68GNH4PSEz6QKkkg6nEeRj9xU%3d


kam

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Re: Slow Increase Fan startup (Fade in?)
« Reply #12 on: May 01, 2011, 09:56:56 AM »
The BC548 will only amplify the current for the capacitor's charging voltage and will dissipate very low power. R2=33KOhm @ 12v, so maximum current would be 0.36mA, and if it had to dissipate all power it would be 4.32 mW.  Nothing. It is the BD243 which will do the hard job, but if you see the specs, it is a badass transistor. You will certainly need a heatsink for this

Ceyarrecks

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Re: Slow Increase Fan startup (Fade in?)
« Reply #13 on: May 01, 2011, 23:15:48 PM »
sweet!
thanks, I have the heatsink in mind.

just waiting for the items to be delivered now ;)

will reply back upon completion.

CAH