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Variable fan speed circuit

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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Topic: Variable fan speed circuit
    Posted: 14 July 2017 at 9:43am
Anyone have some schematic for a simple variable fan control that can be fitted to amplifier that does not have any fan cooling?

Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713
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APW View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote APW Quote  Post ReplyReply Direct Link To This Post Posted: 14 July 2017 at 10:29am
I have something from a piece of equipment I designed about 10 years ago... It uses a L200 voltage regulator and a 1K@25C ntc thermistor. I seem to remember the maximum input voltage being 28Vdc and the fan voltage is 24V.
Here is the schematic if its any good.


The circuit was designed for a specific industrial application so probably not optimised for your application, the incoming supply was rectified but not smoothed hence C4 being largish, if your supply is smoothed you could probably do away with C4 and make C1 much smaller (10s of uF), R3 & C5 acts as a soft start and R2 sets the current limit.

R9 and D1 are just for a visual indication of the equipment’s Temperature and can be removed.


Smile


Edited by APW - 14 July 2017 at 4:46pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ceharden Quote  Post ReplyReply Direct Link To This Post Posted: 14 July 2017 at 2:56pm
Might be worth checking out the one on the Crest CA series schematics.

Depends what kind of temperature sensor you want to use, thermistor vs pre-linearised sensor IC.  Slow PWM (tens of Hz) works quite well for brushless motor control.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 15 July 2017 at 12:01am
you could do what HH did and use a Papst variable speed fan. Comes with the correct thermistor n everything
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sajti Quote  Post ReplyReply Direct Link To This Post Posted: 16 July 2017 at 7:44am
Bulletproof version, based on Crest PROX200 fan driver.
V2 is LM35 thermal sensor. LT1086 can be LM317.

Sajti
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Greg32 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greg32 Quote  Post ReplyReply Direct Link To This Post Posted: 31 July 2017 at 3:56am
I have used this one successfully on two different amplifiers. the 12v fan will start as the temperature  of the heatsink rises until full speed at your predetermined temperature. Greg
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Post Options Post Options   Thanks (0) Thanks(0)   Quote service dept Steve Quote  Post ReplyReply Direct Link To This Post Posted: 31 July 2017 at 8:19am
I'm wondering if this is the level of "simple" that was asked for, maybe a bi-metalic switch bypassed by a suitable sized resistor (for a low voltage dc fan) or a capacitor (for higher voltage ac) would provide a usable two speed set up?
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radi View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote radi Quote  Post ReplyReply Direct Link To This Post Posted: 14 August 2017 at 1:39am
Altec 9444 fan circuit.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 40Hz Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2017 at 3:06pm
Would it be cheating to put in a temperature controlled PC case fan and place the thermistor wherever yields the right result?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote radi Quote  Post ReplyReply Direct Link To This Post Posted: 12 September 2017 at 12:20am
^ Nice just add a 12 volt wall wart or bodge in a CheepChyneez® buck converter module and you're done! Some things to note- "quiet" (low rpm) fans spec about half the CFM of higher rpm models. Ball bearing fans are more reliable than fluid (sleeve) bearings, IMO

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