Using 3.3V for fan operation
Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee
Using 3.3V for fan operation
Well just looking around and I think I will try to use the 3.3V output on the Aux Power Connecter (6 socket in line connector) and see if that will drive a fan. Sounds good if I can get them to turn, if they don't turn I will manually switch between 12 and 3.3.
Anyone else tried using the 3.3V?
Anyone else tried using the 3.3V?
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Oh I think I got one of those Aux connectors too. Which pins are for 3.3v?
3.3v is extremely low, but I think it would be useful for 120mm fans, where 5v is just a little noisy.
Many fans don't start @ 3.3v. Shame there is no easy way of getting it to start at 12v for a few seconds and then turn down to 3.3v. That would be perfect!
3.3v is extremely low, but I think it would be useful for 120mm fans, where 5v is just a little noisy.
Many fans don't start @ 3.3v. Shame there is no easy way of getting it to start at 12v for a few seconds and then turn down to 3.3v. That would be perfect!
getting fans to start
this is what i posted a msg about recently. i want to make a circuit to start a fan at a higher voltage and then bring it down to a set level.
i.e. with a 120mm fan there's no way you can start it at 3.3v, it'll need at least 5-6v initially, but once it's spinning you can bring it down.
any ideas how to do this??
i.e. with a 120mm fan there's no way you can start it at 3.3v, it'll need at least 5-6v initially, but once it's spinning you can bring it down.
any ideas how to do this??
capacitor/diode circuit
that sounds promising. i'll see if i can find the page you mentioned.
cheers
cheers
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The decay of a RC circuit is very well defined. This page describing 555 timers may help http://www.uoguelph.ca/~antoon/gadgets/555/555.html
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Something like this should* work:
/* edit - this is a simpler version that does the same thing */
Select C1 and R4 to get the time you like. t ~= .7(R4)(C1).
Note that by making R4 a pot you can adjust the timing.
so for example pick R4 = 50k to keep current low,
time = 2 seconds, then C1 = 58uF.
Making R2 larger will allow the use of a smaller C1. For exampe,
if R2 was 50k C1 would be 22uF.
R5 is optional; it allows adjusment of voltage (like a rheobus).
*by that I mean someone should check my work. I'm not that
smart. I look forward to people pointing out my errors.
/* edit - this is a simpler version that does the same thing */
Select C1 and R4 to get the time you like. t ~= .7(R4)(C1).
Note that by making R4 a pot you can adjust the timing.
so for example pick R4 = 50k to keep current low,
time = 2 seconds, then C1 = 58uF.
Making R2 larger will allow the use of a smaller C1. For exampe,
if R2 was 50k C1 would be 22uF.
R5 is optional; it allows adjusment of voltage (like a rheobus).
*by that I mean someone should check my work. I'm not that
smart. I look forward to people pointing out my errors.