Power Over Ethernet

Wiring_POE_Pixel_Extender.PNG

This method allows you to use one cable for both power and control lines. The power over Ethernet specifications is written for use with 48Vdc and 56Vdc power supplies at 600mA maximum current. The higher the voltage, the longer you can make the cables with out any issues. Using pixels extenders is preferable but not required.

I do not recommend this method for use with 5V or 12V pixels without a local DC-DC converter. The wire size and connector pins are too small to support enough current. Also, using 5V pixels is recommended, since it reduces the required power versus 12V pixels.

This is really best used with two power supplies, a high voltage power supply at the controller and a small DC to DC converter at each string. The high voltage on the cable minimizes the current required to drive the lights. For example, if you have a string of 50 – 5Vdc pixels, the current at the string is 3 amperes maximum (power = voltage x current) or 15 watts. The amount of current varies with the voltage as shown below:

12V = 1.25 amperes
24V = 0.625 amperes
36V = 0.417 amperes
48V = 0.313 amperes

The Ethernet jacks are rated at 1.5 amperes, and normally two pins are used. Nominally for commercial equipment the connectors are derated by 15 percent to 3.0 x 0.85 = 2.5 amperes. This would be the peak current through the cable.

When choosing a DC to DC converter make sure that the module can support 3 amperes of continuous current. The LM2596 is a good example of what not to buy, it supports 3 amperes peak, with 1 ampere of continuous current.

The differential receivers are not DC isolated from the power in the cable, like Ethernet signals. I lost a couple drivers/receivers last year during hookup, but they functioned fine for the whole season. I suspect that the pins in the connector sometimes connect to adjacent pins. So for next year I leaving pins 3/6 unconnected on either side of the high voltage pins (4/5).

Pros:

  1. One Ethernet cable to each display, tested mine setup to 50 feet.

Cons:

  1. Additional cost for DC to DC converters.
  2. Additional cost for pixel extenders if used.
  3. Receivers are not isolated from DC power.
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