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John (John K.)
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March 20, 2012, 04:28:13 PM
 #41

I assume this is a special processing unit built for Bitcoin mining? You just plug it into a USB port and you are good to go?
Huh
I suggest you do some more reading before posting.

Maybe newbies jail should be extended from 5 to 10 posts...
Actually, he is quite correct. It is a FPGA(google that term), built specifically for SHA256-hashing, or Bitcoin mining in this case.

Of course he's "quite correct".

Are we in the mode of stating the obvious now?!
That's _much_ more annoying than simply stating "subscribe".


Then you haven't see the worst questions yet IMHO. He is quite reasonable in his questions already, given that this is the newbies' thread.

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wogaut
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March 20, 2012, 04:42:01 PM
 #42

You realize that this is the newbie board right? I reserve the right to act like an idiot.

 Grin Grin Grin
You just brightened up my day right now, seriously.
Yes, you totally have the full right to ask your question here.
Absolutely right. I should have taken a look at the top of the page and notice the board.
I'll go and get a cup of coffee now, seems I need it.

John's right too, it could be worse...


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March 20, 2012, 05:25:49 PM
 #43

Are we in the mode of stating the obvious now?!
That's _much_ more annoying than simply stating "subscribe".

Bitcoins are not actually coins.

Oh and subscribed.
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March 31, 2012, 03:13:32 AM
 #44

Has there been any change to the power supply unit in Rev3 singles?  Has anyone come up with a way to power multiple units vs using the included PSU for each single?  If you had 10, 20 or 30+ units, you would need to have 10, 20 or 30+ outlets.

Thanks in advance,

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March 31, 2012, 03:51:41 AM
 #45

Has there been any change to the power supply unit in Rev3 singles?  Has anyone come up with a way to power multiple units vs using the included PSU for each single?  If you had 10, 20 or 30+ units, you would need to have 10, 20 or 30+ outlets.

Power bars are cheap. No, the PSU of the Rev 3 Singles is identical to the Rev 2.

Alternately you could use a standard ATX power supply. Each of its 12V lines could power one Single. For example, you could take a PSU that had 4 6-pin (or 8-pin) PCIe connectors and use it to power 12 Singles (each Single takes 12V @ 6A, or 72W. Each PCIe connector has 3 12V lines).

A good 850W or higher supply would work well. You'd have to wire up the barrel connectors (5.5mm x 2.5mm x 13mm) and ground the 'power good' line to get the PSU to turn on without a motherboard, but other than that you'd be good to go. Use at least 16ga wire (not 18ga) to reduce power loss in the cable runs; 6A is a lot of current to run in small wires for more than a few feet.

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March 31, 2012, 07:25:55 PM
 #46

Do you think that this table here is bogus then?

http://www.rbeelectronics.com/wtable.htm

They seem to say that for 12 amps on 12v circuit you could do 18AWG up to 10'.  That just doesn't seem right.   Huh

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March 31, 2012, 08:15:47 PM
 #47

Do you think that this table here is bogus then?

http://www.rbeelectronics.com/wtable.htm

They seem to say that for 12 amps on 12v circuit you could do 18AWG up to 10'.  That just doesn't seem right.   Huh

That table isn't bogus, but is oversimplified. One thing to keep in mind is that the 'length' is actually the return trip length; an electrical circuit is always a loop round-trip, never one-way. If you want a 6' cable going from your PC to your Single, its 'length' is actually 12' (6' to the Single, 6' back to the PC). The other thing to keep in mind is that cable has a resistance, and that resistance depends on (a) the wire gauge and (b) the wire length.

So for that 12' run of 18ga wire carrying 6A, you will lose 0.95V at the load end. That gives you 11V at the Single, not 12V. That's fine in and of itself, but it represents a power loss of 0.95V x 6A or almost 6W just in the wire.

For fun let's take the same run but use 16ga wire instead of 18ga. For 16ga wire, the voltage drop will be only 0.6V giving you a loss of 0.6V x 6A or only 3.6W. It is still significant, but clearly much better than the 18ga case.

So if you want to lose ~6W per Single by using 18ga wire (assuming a 6' cable), no one is stopping you. Use the handy calculator at the bottom of the following link if you want to play with various scenarios:

http://www.powerstream.com/Wire_Size.htm

I think the thing to take away from all this is (a) use the heaviest gauge wire that's practical (I'd say 16ga is the smallest you want to go, regardless of how short your run is), and (b) make the run as short as possible (i.e. if your Single is going to be 3' from your PC, don't make a 6' cable for it).

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April 01, 2012, 01:40:25 PM
 #48

That table isn't bogus, but is oversimplified. One thing to keep in mind is that the 'length' is actually the return trip length; an electrical circuit is always a loop round-trip, never one-way. If you want a 6' cable going from your PC to your Single, its 'length' is actually 12' (6' to the Single, 6' back to the PC). The other thing to keep in mind is that cable has a resistance, and that resistance depends on (a) the wire gauge and (b) the wire length.

So for that 12' run of 18ga wire carrying 6A, you will lose 0.95V at the load end. That gives you 11V at the Single, not 12V. That's fine in and of itself, but it represents a power loss of 0.95V x 6A or almost 6W just in the wire.

For fun let's take the same run but use 16ga wire instead of 18ga. For 16ga wire, the voltage drop will be only 0.6V giving you a loss of 0.6V x 6A or only 3.6W. It is still significant, but clearly much better than the 18ga case.

So if you want to lose ~6W per Single by using 18ga wire (assuming a 6' cable), no one is stopping you. Use the handy calculator at the bottom of the following link if you want to play with various scenarios:

http://www.powerstream.com/Wire_Size.htm

I think the thing to take away from all this is (a) use the heaviest gauge wire that's practical (I'd say 16ga is the smallest you want to go, regardless of how short your run is), and (b) make the run as short as possible (i.e. if your Single is going to be 3' from your PC, don't make a 6' cable for it).


That is good to know.  I had been to the powerstream site before but the max amps for chassis wiring vs. power transmission listings were a little confusing.

This also brought a question to mind.  The wall warts that are supplied with said units really are not giving the BFL a solid 12v then are they?  I understand that these devices have a range of input voltage that it can take but I just assumed that the supplied materials were much more suited to the power design.  The wall warts are usually around 5ft and maybe 18AWG so the BFL really doesn't see a 12v load during normal usage correct?  How will this affect the power transmission wire releasing all this wasted wattage as heat?

I guess I am just trying to understand the details of DC power transmission.  I'll send you a tip Epoch,  Thanks.

Tired of substandard power distribution in your ASIC setup???   Chris' Custom Cablez will get you sorted out right!  No job too hard so PM me for a quote
Check my products or ask a question here: https://bitcointalk.org/index.php?topic=74397.0
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April 01, 2012, 11:57:49 PM
 #49

This also brought a question to mind.  The wall warts that are supplied with said units really are not giving the BFL a solid 12v then are they?  I understand that these devices have a range of input voltage that it can take but I just assumed that the supplied materials were much more suited to the power design.  The wall warts are usually around 5ft and maybe 18AWG so the BFL really doesn't see a 12v load during normal usage correct?  How will this affect the power transmission wire releasing all this wasted wattage as heat?

I guess I am just trying to understand the details of DC power transmission.  I'll send you a tip Epoch,  Thanks.

Thanks for generous tip, Cablez. Completely unnecessary, but certainly appreciated.

Regarding the BFL wall warts: I don't have one to dissect, but I've seen detailed photos. The 12V line from the power brick is no more than 2.5'-3' long, and the cable itself looks pretty beefy ... I'd guess it is heavier than 18 gauge. So there probably isn't much loss in that short cable.

BFL has stated elsewhere that the Singles themselves take 70W DC but, due to the inefficiency of the supplied wall wart, it pulls 85W at the wall. That's an efficiency of 82%. If you were making your own multi-drop supply, the ATX 80+ Gold has efficiencies approaching 90%. So at most you'd be saving 8% power, or 7-8W per Single. I'm not sure the expense of a $100 ATX power supply is worth it. Say it will power 12 Singles (740W DC, 825W at the wall). Your power savings over 12 stock wall warts would be about 12x8W or 96W. Daily that's 24x96=2.3kWh. Assuming the North American average of $0.11/kWh, that's $0.25/day. Or $92 savings per year.

So it seems that in the long term (1+ years) it could pay off. But that's assuming you are powering 12 Singles. If you are powering less than that, your savings would be proportionally less and your ATX PSU would take longer to pay back. The ATX PSU does have the advantage of having less clutter (you only need 1 power plug total, not 1 per Single).

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April 02, 2012, 12:06:51 AM
 #50

Not to mention that most miners probably have 1 or 2 spare or underutilized PSUs anyway, if they are looking at FPGAs, so that cost most likely becomes moot.  Cheesy

For me, when I see setups like xiangfu's Icarus haven, I look at all the cables and go batty.  Undecided    I would much rather utilize my ATX PSUs and keep it as clean as I can.

Also, don't fret about the tip,  Bitcoin is meant to be spent.  Grin


Tired of substandard power distribution in your ASIC setup???   Chris' Custom Cablez will get you sorted out right!  No job too hard so PM me for a quote
Check my products or ask a question here: https://bitcointalk.org/index.php?topic=74397.0
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April 07, 2012, 01:52:47 AM
 #51

I will be running my miners on solar. The plan is to run them pure DC, not dc to inveter to psu back to DC.
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April 07, 2012, 03:52:39 AM
 #52

I expect delivery in about a month, yes, that leaves ~8 months... and power cost is 0, since they will most likely be housed in my DC.  But even factoring in power, depending on what BTC prices do, it may be paid off sooner (or later if the fall is dramatic)  I based my calculations on $4/btc.

Hmmm, my calculation on $4 per BTC and 0 electricity puts it at 282 days ROI?

How are you doing yours? Maybe I oversimplified mine?
1. Network Ghash/s    11242
2. value per coin            $4.00
3. coins per reward    50
4. rewards / day            144
5. reward / Mhash/s    0.00256 ((4*3*2)/(1*1000))
6. elect rate $ / kWh    $0.00
7. rate                        832 Mhash
------------------------------------
 $2.13 per day = 282 days which also assumes the network rate does not increase. I am really thinking I should revise all my projections now with all the FPGAs coming online.

I'm not questioning your numbers, just checking that my reasoning is not drastically off somehow and trying to become enlightened before my CFO (wife) takes a look at my business plan (crazy idea to buy a minirig or 2).

Not mining since 6-26-2012
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April 07, 2012, 11:53:31 AM
 #53

I have ordered one Single for myself to UK, but with the mini rig now out and using second generations chips, I am considering canceling the order and getting the mini rig instead.
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