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Where can I draw 5V for a fan ?

PostPosted: Sat Mar 22, 2014 10:01 pm
by mgt6910
I have a fan to cool the board as per Gen0 advice. Where can I take 5V from the board?
My power supply supplies 4A 5V, and the fan needs 0.03A.

Re: Where can I draw 5V for a fan ?

PostPosted: Sun Mar 23, 2014 6:31 pm
by 9600
If you solder a link into J15 that will connect the adjacent mounting hole pad to the 5v rail, and you can pick up ground from any of the other 3 mounting hole pads.

Cheers,

Andrew

Re: Where can I draw 5V for a fan ?

PostPosted: Tue Mar 25, 2014 4:35 am
by hsauro
I didn't quite understand your description of hooking a fan up to 5v. On the board J15 has two holes, a square and a round one, are they both connected to 5v? Are you also saying that the mounting pad next to it is ground? Looking at the board itself I don't see the mounting pad going to ground.

Any advice appreciated.

Herbert

Re: Where can I draw 5V for a fan ?

PostPosted: Tue Mar 25, 2014 9:49 am
by 9600
If you solder a very short piece of wire to connect the two pads of J15, this will route 5V to the mounting hole pad next to it. The other 3 mounting hole pads are permanently connected to ground. So you can then power a fan by picking up 5V and GND from mounting hole pads. I did this by putting M3 solder tags on the ends of the fan wires, and then placing these onto the pads, with hex nylon spacers on top and M3 nylon screws coming up from underneath.

I will be getting some pictures of this setup to make it easier for people to replicate!

Cheers,

Andrew

Re: Where can I draw 5V for a fan ?

PostPosted: Tue Mar 25, 2014 6:47 pm
by Calle
Is this safe to do if you stack several Parallellas on top of each other with the supplied stand-off legs?

Re: Where can I draw 5V for a fan ?

PostPosted: Tue Mar 25, 2014 7:11 pm
by 9600
Calle wrote:Is this safe to do if you stack several Parallellas on top of each other with the supplied stand-off legs?


If you're powering each board via the barrel jack and separate PSUs, and using metal stand-offs between boards, I'm not sure it would be a good idea to fit J15 on them!

I'll leave it to aolofsson to comment further.

Cheers,

Andrew

Re: Where can I draw 5V for a fan ?

PostPosted: Fri Mar 28, 2014 6:16 pm
by FHuettig
I would agree with Andrew that it's not a good idea to power multiple boards with individual power supplies and then short all those supplies together via metal standoffs. It might work but it's not clear if the supplies would play together well especially if they might not be powered at the same time or if one fails. I can suggest four alternatives:

  • Use the metal standoffs, but only bridge J15 on one of the boards. This will keep the power isolated between the boards but allow you to pull fan power from that standoff. Just don't forget and use multiple boards with J15 bridged, AND be sure not to accidentally short the power by mounting the standoffs to a metal plate.
  • Use metal standoffs all around, tie the two pads of J15 together on all boards, and use one beefy 5V supply for all boards. Attach the supply to the standoffs rather than trying to supply N boards through one barrel connector, and again make sure the standoffs are not shorted by a metal enclosure, e.g.
  • Use nylon standoffs as Andrew said, even if you only use nylon for the one location that has power (near J15). Then the power is isolated between the boards and you can pull fan power from any one board as long as J15 is bridged on that board.
  • Rather than using the mounting holes, you can pull power from wires soldered into TP15 (+5v) and TP14 or TP12 (both GND). TP15 is located between the ethernet connector and the adjacent mounting hole, next to the serial header, the silkscreen is cut off so it's not obvious. TP12 and TP14 are on the opposite side of the board and clearly marked. This has the advantage that it doesn't force you either way regarding mounting-hole power, but it does mean you end up with wires soidered directly to the board. You can always place a small connector between the board and the fan if you want/need to disconnect the fan.

-Fred

ETA: New first option.

Re: Where can I draw 5V for a fan ?

PostPosted: Sat Mar 29, 2014 3:23 pm
by mgt6910
Many thanks Andrew, I will try this as soon as the fan arrives (1 month back-order......)

Re: Where can I draw 5V for a fan ?

PostPosted: Tue Apr 08, 2014 12:01 pm
by mgt6910
I'm all ready to go assembling the Parallella with fan into the case. I guess the name "mounting hole" should
have prepared me for a problem fitting a solder-tag using a plastic bolt to a hole required for mounting purposes ! The second picture of Step 3 of the assembly guide shows a mounting nub occupying the 5V hole.

I'll try the solder plus connector suggestion from FHuettig.

As a Gen0 owner,might I suggest that the phrase "we do recommend using some kind of fan" in the Quick Start Guide should be backed up with a practical implementation proposal?

Re: Where can I draw 5V for a fan ?

PostPosted: Tue Apr 08, 2014 8:25 pm
by pgater
There is no way I will risk damaging my board, when it is delivered, by trying to solder on a connection for a fan. :mrgreen:
I am however intending to buy a powered USB hub for keyboard, mouse and fan by modifying a spare USB cable as demonstrated in this link :-

http://www.instructables.com/id/USB-Fan ... puter-Fan/

I intend to fit proper connecters to the wires and may use an old fan from a P1 system or buy a new fan, depending on what fits the case I have ordered. :D I note GCeline has also travelled down this route in this post, but appears to have used a soldering iron :-

viewtopic.php?f=12&t=1038&p=6587&hilit=fan#p6587

I hope that this is a workable alternative for customers like myself who are loathe to use a soldering iron on their board immediately after delivery! :D

Regards,

Paul