how to choose correct power supply for led strip


The power supply also named as a transformer or driver, is one of the most important components of an LED system. Using the wrong type of power supply can not only damage your LED product but can also be a very dangerous fire hazard. It is also important to know your input AC Voltage and be certain that it coheres with the products requirements. Determining the right power supply is fairly simple when you follow these few steps.

1. Choose the correct voltage:

The DC voltage of your LED product is a key element in determining the correct power supply that you need to purchase. Longjann tech offer constant 5VDC, 12VDC, and 24VDC power supply for LEDs, and 24VDC. Normally, Most LED display screen are require 5VDC, LED Strip Lighting as well as most of LED Modules require 12VDC with some new 24VDC strip light additions, and most of Wall Washer LED products require 24VDC.

2. What type of constant voltage power we need?

The common constant voltage power for led strip in the market are: waterproof power supply, industrial power supply, plastic case power supply (AC/DC adapter).
You should be clear that where will the strip be placed before you purchase the led strip lights? Indoor or outdoor, dry, splash or wet areas is determine by the IP rating of the strip.
Industrial power supplies are Non-waterproof IP20 (popular) – perfect for indoor use and in areas without humidity and dust but if there is fan on the power. It should be a little noise in an indoor environment. Plastic case power supply is perfect for indoor use (quiet) but the cost will be much high if the output power is big. We have a variety of Plastic case power supply (wall plug style & desktop style) in 5VDC, 12VDC and 24VDC, intended for indoor use.

3. Calculate the total Power Consumption

This can be calculated by using the wattage per meter or ft information for each flexible LED Strip light. Simply multiply that variable by the products wattage spec and then add an additional 15% to 20% on top of that in order to not overdrive the power supply. (i.e. a 100 watt led driver should only be loaded with LED strip lights with a wattage draw of 85 watts at the most).
Example: Total wattage of 5 meters of 60 LEDs per meter SMD LED 3528 is as follows:
4.8 watts per meter x 5 meter = 24 watts so a 30 watt led driver will be sufficient. (Kindly note, you don’t need a super higher power, such as 45 watt for 24 watt, the price will be higher for 45 watt one.)

4. Voltage drop

Normally, SMD 3528 LED strip lights, its connection distance up to 20 meters, however, SMD 5050 one can work with a maximum connection distance of 15 meters. Why? Besides LEDs, there also has resistance/ dynatron on the PCBs. The most important things to consider when connect LED Strip lights is the effect of what is called “Voltage Drop”

Voltage drop describes how the supplied energy of a voltage source is reduced as electric current moves through the passive elements (elements that do not supply voltage) of an electrical circuit. Whenever a current is flowing, the current will meet dynatron, which will impede its flow, the amount of voltage loss through the entirety of a circuit, or even a part is voltage drop. In low voltage lighting systems such as LED strip lights, voltage drops occur because the input voltage from the power supply gradually decreases over the length of the strip.

The longer the flexible led strip light is, the more resistance the current has to overcome; hence it loses voltage along the way. If the flexible LED strip light runs off a 12-volt power supply, then you have 12 volts going into the strip light system at the start but the other end will not have 12 volts due to the voltage drop.

Voltage drop is a function of wire length, wire thickness, and the total watts of power used by the flexible LED strip lights. A reduction of brightness and color accuracy in longer flexible LED strip lights is due to excessive voltage drop. The excessive voltage drop may result in unsatisfactory operation of, and damage to, electrical outlets and the flexible LED strip tape lights. The distance from the power source to the desired end distance of the flexible LED strip tape is called a run.
Shorter and/or thicker wires will raise the brightness and color consistency to the strip lights’ full potential.

Solution to voltage drop

One solution to a voltage drop issue is to run the LED strip lights in parallel. Kindly note, if you need connect long led strip lights, we recommend 24V DC working voltage, its voltage drop less than the 12V DC one. Below connection drawing for your reference:

connection of led strip lights in parallel.jpg

Not only parallel connection, but also connect each end of strip light to the power supply

led strip parallel connect.jpg

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