The following factors determine the length of tape you can run:
- Voltage: Be aware of Voltage Drop. Though this does not limit the length of tape you can run, it will lower the intensity of the LEDs furthest away from the Pixel Controller. You can also inject more power into the tape, which will resolve the voltage drop’s effect on the LED units.
- Watts: LED tape has a total Watt draw for when all LEDs are at full intensity per meter. Total Watt Draw per Meter / the Power Supplies capabilities = Maximum Length. You can also inject more power into the unit further down the LED tape.
- Data: Depending on the number of channels you can control from the Pixel Controller. Channels Per Meter / Pixel Controllers max channel = Length (in meters) that can be controlled. This is the only defining factor that cannot be extended.
Number of DMX channels required
Unlike standard RGB tape or fixture, each pixel has its own chip which enables it to be controlled to respond individually. Allowing each LED to be a different color or intensity across a length of Pixel Tape or fixture.
Each pixel normally takes up 3 (RGB) or 4 (RGBW) channels per chip, though in some cases this can be a lot higher especially if the pixel supports 16-bit dimming.
It's always helpful to remember this quick reference to how many pixels can be in a single DMX universe based on the colors in the tape:
- 170 RGB Pixels = 510 DMX Channels = 1 DMX Universe
- 128 RGBW Pixels = 512 DMX Channels = 1 DMX Universe
Pixel controllers are often measured by Universe (512 Channels).
We take a pixel controller’s output universe count, for example, 4, and times that by 512 (2,048).
We then divide that number (2,048) by the number of channels per Pixel (3 – RGB) which is 682. This is how much pixels we can control from that single output.
If the pixels are on a pixel strip with 60 pixels per meter, we can take the number (682) and divide it by the number of pixels per meter (60). This means that from that output we can control 11.3 meters of pixel strip.
Fuses:
Pixels and pixel controller’s connectors can only handle a certain amount of current (A), it is therefore recommended to break down pixels runs into smaller sections, and add protection to each element in the form of in-line fuses. Refer to the pixels and pixel controller’s datasheets for their maximum current rating.
Voltage Drop
Voltage drop occurs when there is not enough voltage running through the pixels to adequately power them. As voltage travels down the cable from the controller to the first pixel and between each pixel, due to electrical resistance, the voltage constantly decreases. Eventually, it reaches a point where the voltage is no longer sufficient to power the pixel to operate normally. - This is especially noticeable when the pixels are driven to white (all channels at full). Compare the pixels datasheet to understand the voltage range required with reading from a voltage meter to ensure that the correct Voltage is maintained. Additional power injections can be introduced down the line to reinject the correct voltage or consider reducing cable runs/using thicker cabling to reduce the effects of voltage drop (more on these below).
Analogy: Imagine a clothesline that you want to dry some laundry on. First of all, you tie one end of it to your balcony railing on your house. Then you get your nearby neighbour to let you do the same on their house at the same height (this represents the power injection at the start and end of your pixel run, where the voltage is at its optimum). The clothesline is now level at 5m off the ground (this represents the 5v tape we are using, one meter for every volt). Now add some wet towels to the line, this will cause a drop in the middle of the line (representing our voltage drop). If we can prop the middle of the line up back to 5m this will significantly reduce the drop (this prop represents a power injection). If the drop is still too low, we could either add more props (power injections) or get a stronger rope (use thicker cable).
We recommend using a voltage drop calculator and carrying out real-life tests to check your installation for voltage drop prior to carrying out the full installation.
Reinject power
Power injection is required when the voltage on LED pixel tape becomes too low. Low voltage can cause various issues with LED tape including colour shift and drop in brightness the further away from the power source. Power injection is a method of ensuring a sufficient voltage reaches all parts of the strip to ensure optimum performance.
Recommendations for when to inject power for each of ENTTEC’s pixel strips is referred to in ENTTEC’s tape installation guide. Figures stated within this guide for both single and dual power injection are based upon real-world testing, where recommendations have determined factoring in a length of cable 3 meters or shorter between the power supply and the first pixel on the strip. If you require run lengths of pixel tape more than the recommended single power injection method the dual Injection method should be used as described in the pixel tape installation guide. If you are running longer lengths of tape that extend beyond the recommend dual power injection method (injecting at the beginning and end of a continuous length of LED tape). ENTTEC recommends integrating a second power supply.
If a higher length of cable is required between the PSU and re-injection point than:
- 5v at a maximum of 4 meters
or - 12v at a maximum of 8 meters
It is recommended that a second PSU is integrated into the system.
ENTTEC recommends cable length is minimized wherever possible to reduce the impact of voltage drop before reaching your tape.
1.5mm / AWG 14 size stranded cable is the minimum recommended for all PSU -> tape connections.
