The terms “positive” and “negative” wires can be confusing in electrical work. Their meaning depends on whether you’re dealing with Alternating Current (AC) or Direct Current (DC) circuits. This article clarifies the difference and explains why it matters, especially with the increasing popularity of LED lighting.
In standard household AC wiring (110-120 volts), the black wire is “hot” carrying the current, while the white wire is “neutral,” providing a return path. A third, bare copper wire serves as a safety ground. While not technically positive and negative, in AC, black is often associated with positive and white with negative. This is a simplification, as AC current alternates direction, but it’s a useful analogy for basic understanding. These color codes are commonly found in BX and Romex/NMD90 cables.
DC circuits, commonly found in electronics and low-voltage lighting like LEDs, operate differently. Here, the red wire consistently carries the positive voltage, marked with a “+” symbol, and the black wire represents the negative or ground, often marked with a “-” symbol. This convention is widely accepted in DC electronics.
The confusion arises when connecting LED lights, which are DC devices, to AC power sources. LED lighting often uses external power supplies/drivers. On the AC input side of the power supply, the black wire connects to the hot AC lead. However, on the low-voltage DC output side (typically 12-24V), the black wire correctly represents negative, and the red wire represents positive. Incorrectly connecting the black wire to the positive terminal on the DC side will prevent the LED from functioning and might even cause damage.
Unfortunately, a concerning trend has emerged where some LED products, primarily from certain overseas manufacturers, use black and white wires but reverse the standard DC convention, making the black wire positive. This deviation creates significant confusion and potential for miswiring.
This likely stems from misinterpreting online resources about AC wiring and applying those principles to DC circuits. While black is associated with the hot lead in AC, this doesn’t translate to DC electronics. In DC applications, red should always indicate positive and black negative.
To avoid confusion and ensure proper functionality, always adhere to the established DC wiring convention: red for positive (+) and black for negative (-) when working with LED lighting and other DC electronics. This practice prevents damage to sensitive components and guarantees correct circuit operation. Remember to consult the manufacturer’s instructions for specific wiring guidance for your LED product.
