Amplifier cooling, Dx variable speed fan blower

[destroyer X]

I found fan blower noisy, and sometimes needed, and i have faced that need once again while working with a high power prototype.... the solution was the use of blowers because heatsinks not big enougth.

But listening low volume, the blower noises was there... buzzing...bothering.... even when not needed... even when i was playing 1 watt peak.... and the blower was operating with smaller voltage than it's normal rated voltage... i tried 8 volts...also have tried 6 volts...no way!

Then i decided to make something simple... using the audio output as an energy generator to drive the motor.... when our amplifier has too much power, or exagerated power...much more than we need..then we can have some of this power to be used for auxiliary circuits.

A rectifier was used... very simple and nice.... well... simple and cheap is always interesting to my eyes, heart and soul.... audio is rectified and filtered..and then i can power the fan with that energy... a resistance in series is there not to affect power amplifier performance..fourier show me that was unnafected..also AC graphics was fine too.... we have just lost 200 miliamps..when the amplifier can put out 20 to 40 amperes.... so, this is not something to worry about as waste of power.

The video show schematic, also the "thing" operating...simple..no chips..no logic circuit..not triggers, switches, delays, memories.... simple..the way it can be and the way it is working.

I have not used the voltage regulator..but for sure will operate fine...have only to use high voltage transistor and dissipation there may reach 11 watts...so a good heatsink should be used to the series pass transistor...but average power there will be very small..not too much heat there to worry about too....current is around 200 miliamperes to drive motor full speed...and average voltage will not be so big to home use...less than 400 miliwatts will be what you gonna have listening at home..even when driving hard your speakers... 11 watts may be while pumping full power... and more than 50 volts rms audio output...not very often to home use.

When low volume...low AC in the output... low rectified and filtered DC voltage will result...voltage will be smaller than zener voltage (select the zener according your needs and decisions about..your motor voltage is the reference to decide about)..so.... will feed blower with very small speed...it may be even stopped.... but this will happens when you do not need cooling..also "while you do not need, or want, noise from fan blower"... the speed will be "modulated" by the audio power...more power represents more speed and more noise...but that noise will be keep hidden by the high volume of sound....so...the circuit does the job...and it is very clever inside it's own stupidity.

Video explains (or try to) the whole thing:

YouTube - ‪Dx variable speed blower for audio amp. cooling‬‏

Enjoy the new series of " Dx Corporation Gadgets for our enjoyment and fun"...subscrive to uncle charlie channel please:

YouTube - ‪destroyersoueu's Channel‬‏

regards,

Carlos

[bogdan_borko]

What a brilliant idea, you should apply for a patent!

[destroyer X]

because i am not an engineer...this way i can do these things.

Enginners may need to produce sophisticated things... using microprocessors, comparators, op amps, switches and so on.... a huge circuit they can make.. but this is expensive, reason why we are not having these things, much often, in amplifiers around.

Simple solutions are funny.... i agree.... people have laughed about Darlington and others too...they laugh about Einstein too...why not to laugh about uncle charlie?.... you are welcome.

300 guys already watched the video..if 1 percent use the idea i will be already very happy.

Be confortable to laugh...but in secret you can build and use..... ahahahahaha!

regards,

Carlos

[wahab]

Originally Posted by bogdan_borko

What a brilliant idea, you should apply for a patent!

Generaly, i dont see any valuable contribution coming from
you , apart perhaps some discutable entertainment directed
sentences like this one....


More on topic, using the output level as signal to command
a fan is common practice, but it s way better to put a little
circuit comprising a serialy connected resistor with a diode
as rectifier , a filtering cap, and then a darlington as switch
for the fan.

Using the darlington as emitter follower, the vout max can be
settled with a zener at its base to ground while max current
can be settled with a resistor in serial with the fan or with
the darlington emitter , the latter case transfering the thermal
dissipation to the darlington rather than to the resistor.

The cap size will provide a welcomed hysteresis, i.e, if the
amp output power is brutally reduced to 0 , the fan will
very slowly reducing its speed such that the stll warmed
amp will continue to be fan cooled for a few dozen second
to two minutes , depending of the cap s value...

[destroyer X]

i am glad you like uncle charlie ideas and contribute to make them better.

I do think your contribution was nice and valuable.

regards,

Carlos

[wahab]

Hi ,Carlos...

Well, this version is better since it allow use of a low value cap
to settle the falling time.
With 10uF , it should be about 50/60sec..
Thingy is very easy to experiment, anyway..

[currentflow]

An interesting idea Carlos. Not a criticism, but do you not think that the constant acceleration and deceleration of the fan with audio content may shorten its life?

Seeing as your design doesn't measure the actual heatsink temperature, the fan will need to run on somewhat longer after the dissipation peaks have passed. The amount of delay being dependent on the heatsink size and the amount of energy being dissipated and the air flow. Perhaps a variable resistor to adjust the delay time might be an idea. This would allow the design to deal with different heatsink and fan sizes.

Regards,

currentflow

[destroyer X]

A simple idea only... as i told clearly, a gadget..something to play, to have fun, to enjoy...nothing too much serious..but cheap (now cheaper because of Wahab) and interesting.

Yes Wahab, you made much better... we can install two fasn in series because of voltage present there in the colector... higher than 12 and lower than 50.....the supply you pointed ( i will look your schematic once more ) looks to be a 50 volts supply...maybe that supply is mine rectifier and filter input section ... or maybe an auxiliary supply... can be also voltage from the power amplifier main power supply..from supply rail.... well...anyway, it is nice and very interesting to play..... i may give a try on that...nice darlington design... people laughed about Darlington...the man died poor and abandoned... he have not registered his idea.... bell laboratories (i think) had his idea for themselves.

thank you,

regards,

Carlos

[wahab]

Hi , Carlos

The darlington along with the emitter resistor and the zener will
act as a current generator of about 200mA , thus you can put either
one, two of even three fan in serial , provided the supply is high enough
to take account of about 36V drop voltage with three 12V 200mA fans
plus the 14V or so that will remain at the darligton collector.

The more the fans in serial, the less the darlington will dissipate.
With a single 12V/200mA fan and 50V PS , the darlington will dissipate
about 8W , while with two serial fans, this will be reduced to 5W ,
and 3W for three serialy connected fans.
so it must be mounted preferably on the main heatsink and use of
two or three fans is recommended.

With lower supply voltages, TDP will be less, of course, as well as
fan number capability , two with 35V PS.

Have FUN!

[Bigun]

I like this idea, definitely worth trying. I agree, simple is good and within the spirit of DIY. Now one caution, maybe best to see with experiments, but a colleague of mine threw out his home theatre amplifier because it had a fan that changed speed with power. He found he could hear the darn thing accelerate when the music got louder and although this wasn't very noticeable at first, after a longer time his brain became aware of it, and the more time passed the more his brain became irritated and in the end it was infuriating. You may have a quieter fan.