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LED strip wiring

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  1. Mar 23, 2017 #1
    Hi, I want to buy 5 meter 60 LEDs/m LED strip here and this is the recommended circuit. The strip needs 5V. In their description they say 60 LED is 18W so I need 20A DC power supply.

    Can I send 20A 5V DC directly in the strip? Will it fry the strip? Also, for the ground wiring, is this where the electrons come back in the power supply with 0V? If so I suppose I don't need a big AWG wire? How to calculate how big AWG I need for ground wire?
     
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  3. Mar 23, 2017 #2

    Baluncore

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    Input voltage: DC5v; 60 leds/m; dissipates 18 watt/meter; 5 metre * 18W = 90 watt; 90W/5V = 18 amp

    The LED strip will take what current it needs from the fixed 5V supply. That will be about 18 amps, it will vary with temperature.
    You will connect the 0V and the +5V to the LED strip with two wires of the same gauge. A 20 amp low voltage circuit will need two wires, each with a cross section of 4mm2.

    The 0V side of the 5V circuit will be connected to the local earth or ground at the power supply. The ground and control wires from the controller to the LED strip can be much thinner than the power supply cables.
     
  4. Mar 24, 2017 #3
    I think it's a 'no'.
    I admit it's just a googled knowledge, but the strip connectors I could find are only for a few A current. There was one for 5A, and that was already 'high current support'.

    Some more digging will be required I think. What kind of connectors/wires does those strips has and what is the maximal current for them?
    Then you will have to limit the strip length for one connector accordingly.
     
  5. Mar 24, 2017 #4
    But the isn't the included connector just for convenience? I could just solder my bigger AWG wire that supports 20A directly on the first LED?
     
  6. Mar 24, 2017 #5
    The track width on the flexi PCB of the LED strip is also designed with some kind of maximal current in mind.
    Which is most likely something similar like the actual wires and connectors.
    I would not try to hack this. Not at 5A <-> 20A disparity.
     
  7. Mar 24, 2017 #6

    anorlunda

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    Are you sure that is 18w/m, or 18w for all 5m?
     
  8. Mar 24, 2017 #7
    18w / 60 LEDs

    Also I read the adafruit section on powering their neopixels and all they say about high amps is that I may have discoloration at the end of the strip, nothing on anything frying...
     
  9. Mar 24, 2017 #8

    anorlunda

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    One of one on the customer comments on the link you provided said that 144 LEDs drew about 2a. That is close to 18w/300 LEDs.

    Besides, pushing 20a up that strip doesn't sound reasonable.
     
  10. Mar 24, 2017 #9

    Baluncore

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    It is important to note that the circuit diagram shows each long LED strip being fed from both ends. That will halve the current through the connectors to 9 amp.

    The power cable from the power supply will need to carry and distribute the full current.
     
  11. Mar 25, 2017 #10
    But do I really need to connect both ends to ground and 5V for a single 5m strip?
     
  12. Mar 25, 2017 #11

    Baluncore

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    That will depend on the current rating of the replicated strip and the current rating of the connectors you use. It will still work if you drive it from one end, but the connectors to, and the conductors on the strip will run hot, so the reliability and efficiency will be less when driven from only one end.
    Remember that the digital data stream addresses the individual current controllers on each RGB LED, so the data must be linked along the strips in series.
     
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