In the last article, we looked at various options for USB risers to assemble mining rigs. In most of them, at this moment, you can find various connector options for organizing additional power on the 12V line. The most widely used connectors are PATA Power Connect (4 pins per line), SATA Power Connect (15 pins in two lines) and PCIe Power Connect (6 pins in 2 lines). Moreover, in recent models of USB risers, several connectors for additional power supply are installed at once, or only one 6-pin PCIe. In addition to all this, the Sata Power Connect to PATA (PCIe) adapters are bundled with the risers, or vice versa, depending on the add-on connector installed on the riser. power supply. If, when assembling your mining riga, you plan to use or already use Sata Power connectors from your power supply, then you have a great chance to remain without equipment as a result of a short circuit or even the entire room where mining mining is located. Why this happens and how to avoid it, read on.
For a better understanding of how these or other connectors look, let's take a picture of them:
Parallel ATA (PATA) Power Connect or more popular name MOLEX 8981
According to the specifications, such a connection allows the transmission of electric current of no more than 6.5 amperes. Since there is only one 12V transmission line (yellow wire), therefore the maximum transmitted power to a USB riser through this connector will be no more than 78 watts.
Serial ATA (SATA) Power Connect
3 pins are used to transmit 12V at 1.5A each, i.e. maximum 4.5 amperes or 54 watts Molex connector specifications can be viewed at this link
PCIe 6 pin Power Connect
In this connector, all lines are used only for 12V and the maximum transmitted power is 75W.
And so we found out that the SATA Power connector is slightly inferior in its characteristics to other variants (54 W instead of 75 W). We will try to determine whether this is important.
Let's open the Wikipedia page dedicated to the PCI Express standard, where it is indicated that electrical devices installed in the PCI Express X16 slot can count on 5.5 A via a 12-volt line or 66 watts. It turns out any graphics card at the request of the designers can fully utilize this power through its PCI Express connector and the more powerful the video card, the greater the chance that this limit will be used to its fullest.
With the maximum possible load on the riser at 66 W for additional power, the Serial ATA Power Connect connector has the potential to overheat and melt in 24/7 operation mode, since according to the technical characteristics, the maximum transmitted power of such a connector is only 54W.
It turns out only at this stage of comparison of the technical characteristics of the connectors, we get the potential danger of burning all expensive equipment only because we use the adapter from the USB riser kit, on which the SATA Power connector is unsoldered or connect the power supply connectors directly to the riser if the SATA connector is unsoldered Power.
In addition to electrical parameters, the connectors also have mechanical ones, which tell us that the maximum number of connection cycles for all types of connectors does not exceed 50. That is, manufacturers guarantee the technical characteristics of their connectors, provided that the number of assembly and disassembly cycles does not exceed 50 times. It should be noted that the figure 50 is indicated for well-known companies (MOLEX, Tyco, etc.) which use special contact coatings to increase the resource. For unknown Chinese connectors, which are usually equipped with risers, this figure can be easily divided into two or three.
It turns out that even suitable connectors on the characteristics (PATA, PCIe) can melt and lead to sad consequences if they are often used, for example, in test benches.
Now we have considered only one important part affecting security. The second and no less important is the wire. And their main characteristic is the thickness of the core, which is specified in units of AWG. The larger the AWG parameter number, the thinner the wire, and not vice versa, as one might think. For example, it is recommended to use AWG18 wires for PATA Power Connect connectors; in our case, this wire is 1.19 mm in diameter. The maximum current load for such a copper wire does not exceed 16 amps. It would seem that the use of such a thick wire is redundant with a current limit of 6.5 amps in the connector, but you should not forget that the wire and the connector must also be connected. This is precisely the important stage at which everything can be “screwed up”. When stripping a wire from insulation, part of the current-carrying core is often cut off along with the insulation. Further, at the stage of crimping or soldering the wire to the connector connector, the contact between the residential wire and the connector is rarely called ideal, because of which the contact area of the surfaces is almost always less than the calculated one. To eliminate all these factors directly affecting the quality of the final product, wires with a margin were initially laid.
Compliance with the diameter of the wire and the possible current load on it.
Now we take any real riser and look at the complete adapter, in 90% of cases the wire will be of smaller diameter than AWG18 and this is only at first glance, since the cunning Chinese learned how to make thick insulation under which the wire is even smaller than we expected to see, appreciating only the appearance. The use of thin wires reduces the cost of the adapter by 2 kopecks, but adds the potential to melt the connector or wire insulation, which will immediately lead to a short circuit.
From this we can conclude that the use of SATA Power Connect connectors in combination with thin wires of poor-quality assembly (soldering) when creating mining rigs can be compared with throwing matches into a powder keg with predictable consequences and the more powerful the video card is, the more obvious the risk becomes.
This might look like a SATA-SATA connection between the riser and the power supply.
Less fortunate miners can see such a picture.
In the most neglected cases, this option is not excluded.
Conclusion:
The most popular now USB riser version 006 uses a PCIe connector for additional power, because These connectors are always in demand for connecting the video cards themselves, so almost always complete adapters from SATA to PCIe are used. We categorically do not recommend doing this, especially to owners of video cards with power consumption of more than 200W, since in this case, you will get the maximum risk of being left without equipment as a result of the melted insulation of wires and connectors and the subsequent short circuit. To connect the risers to the additional power, try to use the direct connection of the power supply connectors to the riser without adapters, use only PCIe and PATA connectors as the connection. For cases where the use of SATA Power connectors on the power supply cannot be dispensed with, you must buy an adapter with two SATA connectors on Aliexpress, which, by distributing the load, will significantly reduce all the negative consequences of using adapters to risers.
Также стоит знать один нюанс с блоками питания - производители вешают 4 или даже 8 разъемов SATA параллельно на одну линию электропередачи, к которым есть естественное желание подключить больше USB-концентраторов. В этом случае проводка самого источника питания может уже сдаться, поскольку изначально он не был предназначен для подключения таких энергоемких устройств, как несколько видеокарт одновременно. Поэтому не подключайте более двух стояков к одной линии электропитания с разъемами SATA, особенно если у вас есть недорогие блоки питания.
