Infrabasse

Hi,

I'd like to know if 18AWG wire would be sufficient for a 7 hardrive chain.
I'm building a rather big HDD cage and this is what the plans look like so far:


Molex come in 4 connector chains on most PSUs and I'm just hoping 3 more drives won't end up draining too much power for the cables to sustain.
Any thoughts on this?

I'm planning to use these molex connectors and I'm not even sure I'd be able to crimp thicker wire in them anyway ...

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typoknig

I think you would be ok with 18 gauge wire, but if you are building it from scratch then why not step it up a bit just to be safe. I think I would go with a 14 gauge instead.

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Infrabasse

The thing is 14 gauge may not fit the crimp connectors which I suppose are designed for 18 awg.
I could do it with 2 chains of connectors but it wouldn't look as nice.

If numbers help, I'll be looking @ 35W and 14 Amps according to Samsung F1's specs.

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G|F.E.A.D|Killa

i would at least go 16 if you can.

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Infrabasse

I just used this wire calculator
For 3 feet long which is exagerated on purpose and at max current draw (drive spinup) I'll be looking at a 0.27v voltage drop which I would say is acceptable.
The PSU sitting right below the drive, It'd more likely be around 0.1V considering the short cables.

Is this the only data I should worry about or is there other factors to take into consideration?

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shinji2k

How do you get 35W and 14A? Assuming that is 14A of 12V (which is about right for 7 drives at spinup, normal operation would be closer to ~7A) that would be 168W. You will also have ~1A of 5V for each drive. 14A for a 18AWG is a bit high but fine for short bursts. The real problem is that molex pins are only rated for ~8.5A each. Even if you are closer to 7A during normal usage, it's too high for my tastes. It would be much wiser to distribute it over two wires or else you risk burning up your molex pins.

edit: According to this, the F1 draws 22W at spin up but then 6-8W for everything else. Apart from spin-up, normal operation should be fine since you'll only hit ~50W on the 12V wire for seven drives. If you could do staggered spin up to reduce the power draw it would be perfectly fine with one 18AWG wire.

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typoknig

Just snip a couple of strands of the wires off at the connectors, that way you have minimal voltage drop up to each connection, or you could do a staggered spin up like was suggested... I think either would work, but I personally like to build heavy duty, bigger wire may help you in the future for one thing or the other

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Infrabasse

I actually got the 35W wrong, I picked my data from the wrong drive
Here's the drive

So 2.4A per drive and 8.4W read/write
So that 16.8A max (but I can use staggered spin up)
and 58.8W in normal operation
P=U.I so I=P/U
58.8/12=4.9A
58.8/5=11.76A
not sure where most of the power is coming from

Pins will crimp around the cable and lead to individual drives, I wouldn't have thought I needed to be concerned at all about these since to me they'll only be affected by their respective drive power requirements.



EDIT: looks like you thought of the staggerred spinup too
would MDPC sleeve fit 16AWG?

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shinji2k

Heh for some reason I was thinking it was a modular cable with it all going through one pin .

2.4A on the 12V is awfully high for even spin-up. Everything I've seen says the F3 are more efficient than the F1 so 2.4A is way too much compared to the 1.85A for the F1. Also, their read/write power consumption figures are probably combined 5V and 12V. Each drive will draw 2-3W on the 5V for most situations. Add on another 5-6W for the 12V power consumption and their numbers seem just fine.

So yeah as long as you do staggered spin up, 18AWG can handle 50-60W no problems.

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Pearl in the Rough (My on going case mod comp project that I couldn't finish on time)
Actual Power Consumption of a few components I own

Please forgive me, I have SIWOTI syndrome.

A still more glorious dawn awaits. Not a sunrise, but a galaxy rise. A morning filled with 400 billion suns. The rising of the Milky Way.

Infrabasse

I'll be doing this on a Corsair TX850
The molex cables are about 40CM long before their 1st connector and I think I can actually get away without even needing to replace or extend the wire since I only need a very short distance

Thanks for your help guys

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