Lasse Langwadt Christensen
sÃ¸ndag den 16. januar 2022 kl. 22.39.02 UTC+1 skrev jla...@highlandsniptechnology.com:
On Sun, 16 Jan 2022 20:50:15 -0000 (UTC), Cydrome Leader
On Fri, 14 Jan 2022 01:34:35 -0000 (UTC), Cydrome Leader
Has anyone run bldc fans in series? I want to run three 12v fans from
a 48v supply, with a resistor or something in series
I guess I could be cautious and put a cap and a 12v TVS across each
fan. Hmmm, 3 fans and 4 TVSs might work.
Worst case, I can make a 48 to 12 switcher.
Here\'s the idea:
Don\'t do it. They will not share voltage and the losers will burn out on
the first start. Been there, done that. Find 48 volt telecom fans or 24
volts ones and use individual series resistors. Fans are mechanical so
don\'t increase your failure rate by using any sort of chain.
The 35mm fans I want to use seem to only come in 5v and 12v. And the
supply is 48.
I suppose I can make a 48-to-12 switcher on this board. Still, a
series string with shunt zeners ought to work.
If you can go for a larger diameter fan, even mounted at an angle. They
run slower, make less noise and can last longer. This also opens up the
ability to get telecom fans. Fancy options allow for analog or PWM speed
control as well.
If reliability is key, run two fans in series (air flow wise). There is no
major performance difference otherwise. You can even get counterrotating
double thick fan modules as used in servers. The major brand ones like
Nidec are actually extremely reliable at high temps and speed, even with
ball bearings. They really figured figured these things out.
I considered all sorts of ways to use one big fan, horizontal or
angled, and couldn\'t make it work. It would need some sort of ducting,
and the next board is 1.6\" away so there\'s no way to get the air into
and out of a big fan. We do want to shoot the hot air out the rear of
the box, not stir it around inside, another constraint.
We\'re building a mockup for thermal testing. I have no analytical or
simulation tools for a thing like this, and my instincts for air flow
are all mediocre guesses.