2020-10-02 11:17:30 -04:00

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RGB LEDs can draw a lot of current (amps). While most people usually worry about the dangers from high voltage, low voltage + high amperage can be dangerous too, as it can easily become a fire hazard in certain circumstances. Depending on your setup size (the number of LEDs you want to drive), use these tips to help guide your wiring.

There are plenty of guides out there to help with power supply selection, which is out of scope of this page. Size your power supply to your installation, so you don't introduce unnecessary risk. It's better to power 30 LEDs from a 10W (2A @5V) power supply than a 200W power supply, as you don't need to worry about the potential for as much energy flowing through small wires.

As you increase the number of LEDs, you increase the amps your power supply will need to be able to provide. The more amps you're working with, the more you need to be cautious about your wiring and fusing.

For example, if you want to power your installation off a sealed lead acid battery (e.g. a car battery), you need to be very careful about amps. These kinds of batteries can supply hundreds of amps, so you need to ensure that you use fuses and voltage regulators along the way. If you're using USB pocket chargers on the other hand, they tend to be current limited (most provide only 1-2A max) already so you can worry less about fusing there.

Small Setups (< 30 RGB LEDs)

WLED has a great built-in automatic current-limiting feature, set to 850mA by default. If you have a very small setup (< 30 LEDs), you can use this feature to help simplify your wiring and keep things safe. Note: it does this by limiting the brightness, so don't try to bypass it by turning up the brightness.

In most circumstances, it's best to power your LED strip directly from the power supply and wire power to your WLED control board in parallel.

{insert diagram here}

With the current limiting feature turned on and for small setups, you can power the LED strip directly through the USB port of D1 mini or similar board. That is, power comes in to the control board through the USB port and out to a 5V pin. Each board will be a little different, so it may be wise to look around for advice about a specific board. You want to ensure that there are no voltage regulators, diodes, or other components between the 5V pin and the USB port input. You also want to ensure that any PCB traces are big enough that they don't heat up with increased current. Never try to draw more than 1A through a board's USB port like this; the boards really aren't designed for large amounts of current to flow through them.

Medium Setups (30-300 RGB LEDs)

For a medium-sized setup of 30-300 LEDs, you should find a power supply that can provide enough current (see the link above) and make sure to power the strip directly. For setups with more than 150 LEDs, you should consider power injection. Power injection is where you connect multiple wires from your power supply to the strip in multiple places, usually once at the beginning and once at the end. This is needed because the LED strips can only pass a small amount of current through them and you need to ensure that all your LEDs get fed enough power. If your LEDs are dim at one end of the strip or you're losing your blues, you should add power injection.

Power injection

When doing power injection, make sure your wires are rated for the amperage you wish to send over them. You should also check the voltage drop if you're doing a particularly long run. As a rough guide, you should never use anything thinner than 24AWG wire for power injection.

For medium-sized setups, fuses can be smart if your power supply is over 100W. Considering an inline fuse on each power injection line. Place the fuse right after the power supply. That will cause the fuse to blow if the power injection line shorts or if the strip shorts.

Inline Fuses

Inline fuse

You should place the fuse as close to the power supply as possible, on the positive lead. Buy a fuse that's rated just over what you expect your LED strip to draw. For example, if you calculate that your LEDs will draw at most 4.5A, buy a 5A fuse.

First match your power injection wire size with the inline fuse's wire. If the inline fuse comes with 16AWG wire (it's usually printed on the wire itself in small type), you should use 16AWG or thicker wire for your power injection wire. If you use thinner wire, you weaken the utility of the inline fuse and risk your power injection wire heating up in the case of a failure.

To wire in an inline fuse, trim back the positive wire (not ground) of your power injection line enough to allow the inline fuse to be spliced in. Place a cut of heat-shrink tubing over the wire so that the cable can be insulated once your solder joint is complete. Strip and bend both wires of your splice so that they create hooks to mechanically reinforce the joint, then solder. Cover with the heat-shrink tubing and you're done! Now you have a beautiful, professional-looking fused power injection line.

Larger Setups (300+ RGB LEDs)

The more power you're working with, the more you need to be careful about your wiring. If you're using a 150W or higher power supply or multiple power supplies, check out these tips:

  • if using stranded wire and screw terminals, all your wire → terminal connections should be terminated with a wire ferrule. This is because stranded wires can splay and lose tension over time, creating a weaker connection that could lead to sparking. The same is true for tinned stranded wires: the solder can deform and cause a weaker connection. The ferrule will also prevent stray strands from getting loose and causing a short.
  • Always check wire gauge + amp ratings and make sure to overcompensate by 2-3×
  • more, lower-current wires are better than fewer, higher-current wires
  • Ensure that all strips are fused just above their max current. Fuses should be located as close to the power supply as possible.
  • Make sure all distribution wires are neat, tidy, and mounted to a structure. If it needs to be loose to bridge an air gap, minimize the amount of dangling wire as much as possible. This ensures that if you were to have a wire become disconnected, it'll be easy to see where it is.
  • When doing power injection with multiple power supplies never mix two power supplies on the same LED strip. The "why" of this rule is exceptionally complicated, unfortunately: this is because multiple power supplies could have different positive voltages (e.g. 12.1V and 12.3V) or even different ground planes, and mixing the two could cause power to flow in ways that could be dangerous to your equipment. Power supplies generally don't like to be directly connected to other power supplies unless they are explicitly designed for that purpose.
  • Did you add fuses? Add fuses. Seriously.