Brett, you're smart to be thinking about voltage drop over such long runs. Here's a breakdown of the factors involved and how to approach this

1. Understanding Voltage Drop:
LED strips require a specific voltage (typically 12V or 24V DC). Over long distances, the resistance of the copper traces within the LED strip itself causes the voltage to drop. If the voltage drops too low, the LEDs at the far end of the strip will be noticeably dimmer, change color slightly, or even fail to light up.2. Factors Affecting Voltage Drop



LED Strip Voltage (12V vs. 24V)

24V systems have significantly lower current for the same wattage, resulting in much less voltage drop.

Prioritize using 24V strips if possible, especially for long runs. LED Density (LEDs per meter/foot)

More LEDs mean higher current draw, which increases voltage drop.

LED Strip Wattage (Watts per meter/foot)

Higher wattage also means higher current and greater voltage drop.

Copper Trace Thickness (Width of the Copper)

Some higher-quality LED strips have thicker copper traces designed for longer runs. Check the manufacturer's specifications. This is often a key factor.

Power Supply Voltage Tolerance

Most power supplies can be adjusted slightly. You might be able to bump up the voltage a bit (within safe limits) to compensate, but that's just a band-aid.

Ambient Temperature

Higher temperatures increase the resistance of the copper, exacerbating voltage drop. While probably not a huge factor in this application, consider it generally.

3. Approaching the 75' Run Fed from the Center



Effective Run Length

Feeding from the center effectively creates two 37.5' runs.

Calculate Potential Voltage Drop

You MUST calculate the voltage drop. Don't guess. You need:

The exact model of LED strip you plan to use. Get the datasheet! The wattage per meter/foot (or total wattage for the 75' run). This is critical. The voltage of the strip (12V or 24V). Information about the copper trace thickness (ideally). Use a Voltage Drop Calculator

Search online for "LED strip voltage drop calculator." Many are available. Plug in the parameters.

Acceptable Voltage Drop

Generally, you want to keep voltage drop below 10%. Ideally, less than 5%. Some manufacturers will specify a maximum voltage drop for optimal performance.

4. Solutions if Voltage Drop is Too High



Use 24V Strips

This is the best solution, if possible.

Power Injection

This is the most likely solution. "Power Injection" means providing additional power feeds along the LED strip run. Instead of one feed in the center, you might need feeds every 15-20 feet, or even more frequently. You'll need to run additional wires (typically 18-22 AWG, depending on the current) to these injection points. This is the standard practice for long LED strip runs.



Use Higher Quality LED Strips

Strips with thicker copper traces will have less voltage drop. These are more expensive, but worth it for long runs.

Use a More Powerful Power Supply

This is usually not the solution to voltage drop. A bigger power supply won't fix the resistance of the wire. It will simply allow you to power more LEDs, but the far end will still be dim. You will need a suitably sized power supply to handle the total wattage of all the strips plus a safety margin (20% is a good rule of thumb).

Run Parallel Strips

Instead of one long strip, run multiple shorter strips in parallel, each powered from the same power supply. This divides the current. This may or may not be aesthetically acceptable depending on the application.

5. Practical Advice and Examples



Example 1 (Good)

You're using a 24V, low-density (e.g., 60 LEDs/meter), low-wattage (e.g., 7W/meter) strip with decent copper traces. A voltage drop calculator might show a voltage drop of only 4% over the 37.5' half-length. In this case, feeding from the center might be okay.

Example 2 (Bad)

You're using a 12V, high-density (e.g., 120 LEDs/meter), high-wattage (e.g., 15W/meter) strip. The voltage drop calculator might show a voltage drop of 30% over the 37.5' half-length. This will be very noticeable and unacceptable. Power injection is REQUIRED.

6. Dealing with the 25' Run

The 25' run will likely be less of a problem, but you should still calculate the voltage drop to confirm. You may still need to power inject this one.

7. Important Safety Considerations



Waterproofing

Ensure the LED strips and connections are properly waterproofed (IP65 or higher rating) for outdoor use. Pay special attention to the power injection points.

Low Voltage Wiring

Use appropriate low voltage wiring (e.g., CL2 rated) and connectors rated for outdoor use.

Overcurrent Protection

The power supply should have built-in overcurrent protection.

Professional Installation

Consider hiring a qualified electrician, especially for complex power injection setups. Electrical codes vary by location.

Power Supply Location

Keep the power supply in a weather proof enclosure.

In summary, calculate the voltage drop for your specific LED strip and power injection is highly likely for the 75' run. Also calculate voltage drop for the 25' run. Do not proceed without knowing the specific model of LED strip and its power requirements. Flag for review