Hey all,
I was looking at using 3 pin XLR cables to power and control LED strips, using it to run from the arduino and 5V PSU to the LEDs. The cable and connectors need to support 10A at 5V. A lot of cheap cables don't mention the current rating. How do you know if they're going to be safe to use?
From wikipedia it says the connectors are rated at 15A which sounded ideal to use. The connectors look ideal for my project too.
Thanks,
MeatPlatter
If the cable spec mentions wire gauge, you can use that for a guide as to current capacity (look for ampacity tables).
Tyipcally these cables are used for audio signals of microwatts or milliwatts (and micro & milliamps) so nobody cares about the current rating. If you find the wire gauge spec for a cable that might be your best guide. Some manufactures/vendors will specify the gauge and others will not.
Or, you might need to build our own so you can use a large wire and you'll know the gauge.
P.S.
[u]Monoprice[/u] has 16AWG XLR cables. That should be hefty enough for 10A as long as your cable run isn't too long.
MeatPlatter:
... 3 pin XLR cables ... need to support 10A at 5V.
The referenced Wikipedia article says that XLR connectors can support a connection to #14 wire, American Wire Gauge, about 1.6 mm2. The National Electrical Code (NEC), where "National" means "USA," lists #14 copper as able to carry 15 amps at a conductor temperature of 60 degrees C in an ambient of 30 degrees C, enclosed in conduit. In free air, individual conductors, #14 is rated at 25 amps. For #16, about 1.3mm2the corresponding ratings aren't described, but for a 90 degree C conductor temperature, they're described at 18 and 24 amps, respectively. So, if your insulation is rated at least 60 degrees C, you use #14/1.6 mm2, it's not too hot in the vicinity, and your only concern is that the assembly doesn't combust, you're OK.
Switchcraft describes at least some of its three-pin XLR connectors as good for 15 amps, and suitable for #12 solid wire: http://www.switchcraft.com/Specification.aspx?Parent=460.
The Wikipedia also claims that wheelchair chargers often use three-pin XLR cables to carry 2 to 10 amps. If that's true, it certainly argues that at least some XLR connectors are safe at that current. It would be a cruel thing indeed to set a wheelchair afire just when its owner needs it for something really important, like escaping from a fire.
The NEC is a fire code. Its primary purpose is to ensure that electrical installations are generally safe, and specifically, that they don't start fires. It's less concerned with whether or not those circuits work the way you want them to work.
To maintain the voltage at 95% of a nominal 5V - 4.75V - the conductors can only drop 0.25V. At 10 amps, that means that the resistance can be no more than 25 milliohms. #14/1.6mm2 has a resistance of 8-10 milliohms per meter, so the conductors can't be more than about three meters. For #16/1.3mm2, that resistance is 13-17 milliohms per meter, for a maximum length of just under two meters.
You might want to consider whether Speakon connectors would suit you. #12 AWG cables are readily available, also at Monoprice: http://www.monoprice.com/Search/Index?keyword=speakon
For the high end of resistance per unit length for American Wire Gauge sizes, see the NEC, Table 8, here - NEC 2011: Chapter 9 Table 8 - or here - http://records.jonesboro.org/Technical%20Codes/Electrical%20Code/Chap_9.pdf. For values on the low end, caculated straight from the resistivity of copper, try here - Electrical Wire Gauges.
Thanks, that's really helpful!