Alternating Current & Direct Current - Comparison

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The Basics

Low voltage lighting (with the exception of solar lighting) requires a transformer to convert the power from an electrical source to just 12 volts (down from the original 120 volts). The current that then flows from the transformer to the light fixtures will be either Alternating or Direct.

transformer photoeye tapped transformer on off switch transformer on off switch

Alternating Current (AC)

Alternating Current (AC) has a cycle of changing flow and voltage. The current will continually change between positive and negative.

Direct Current (DC)

On the other hand, Direct Current (DC), has a consistent, uniform flow of energy in both voltage and direction.

The wiring needed for low voltage lighting has two strands. In two-strand burial-grade low voltage cable, one strand remains positive at all times and one strand remains negative at all times. When wiring DC-powered lights, it is important to keep the positive connections consistent and the negative connections consistent in the entire lighting layout. This consistency is not necessary on an AC system because the current flowing through both strands will continuously alternating between positive and negative.


An AC Transformer is always recommended to power low voltage incandescent bulbs (Non-LED). It can also be used to power LED lights that are equipped with an AC Adapter Driver. 
DC transformer is typically recommended for low voltage LED fixtures (that does not have an AC Adapter Driver included).

Please Note: 
If lighting that is meant to go on a DC transformer is used with an AC transformer, the lights in the fixture will burn out within a short period of time, sometimes in just a few weeks. Please make sure to double check the “Product Specifications” section on the product page of the light you’re purchasing to determine the proper transformer type.

If you have any additional questions about AC or DC Transformers, please don’t hesitate to call us at 1-888-842-5316 or e-mail support@decksdirect.com.

3900 50th Ave N #100 Minneapolis, MN 55429
1-888-824-5316 sales@DecksDirect.com

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