Thursday, April 4, 2013

LED Sign Tech & Spec: Check The Power! Electrical Supply and Outdoor Digital Signage

-Scott Hofheins

Is the sign getting the correct power? This is one of the first questions I ask when an LED sign is exhibiting strange or seemingly random issues that normal troubleshooting cannot solve. Nine times out of ten the power is found to be the root cause. Unfortunately (in the past) I had to learn this the hard way, spending hours working on solutions that ultimately would fail due to bad power. This can be extremely frustrating for both the end user and the technician.

I hope to help save some time and effort for people with these issues by providing some common power issues that I've seen occur, and ways to recognize and avoid them altogether. We won’t go to in depth about how power works in general, but my earlier post about voltage and amperage, and Deacon’s post on “the silent killer” have additional information on this topic..

To start with, I have found it’s always good to verify the power immediately in the following situations:
  • If the sign is at a special event using portable power, like 208 VAC.  
  • If the sign is using a generator for power.
  • If the sign is blank, and you cannot communicate to it.
  • If the issues on the sign don’t “make sense” after normal troubleshooting procedures.
  • If the sign is on multiple circuits, and only certain sections of the sign are blank, corresponding to the circuits.
Voltage Drop
Any electrical installation Must take voltage drop into account. Electricity travels through wires (conductors) that have a certain amount of resistance. As the length of the wire increases, the Voltage will decrease. This will cause the sign to be under-powered, and will cause issues with the power supplies and internal components.

  • Long distances between sign, and the main source of power.
  • Sign or sign components reboot at seemingly random times.
  • Components work for a certain amount of time, but repeatedly fail.

System Voltage
Electrical devices are configured to work on certain voltage ranges and phases. Most devices in the US work on either 120 Volts or 230 Volts. Although devices can operate within a 10% range either way (ie 115 Volts or 220 Volts), they must stay within that tolerance or damage will occur. In most cases you cannot run an LED sign on 230 Volts that is setup for 120 Volts without major damage to the components and complete failure of the sign.

  • Sign powers on, but runs erratically.
  • Sign will not boot up after power on.
  • Issues with sign components that cannot be traced to a definite cause.

Wire Size
The wire size is extremely important to provide SAFE and adequate power to the sign. If the wire size is too small for the sign’s power requirements you can cause damage to the sign and the electrical system. Voltage drop will occur, and the amperage levels can cause the wire to overheat and melt.

  • Small extension cords, not meant for commercial or heavy duty use. This usually happens if the sign is hooked up for temporary power, or on mobile LED units.
  • Discolored or semi melted wires or connectors.
  • Significantly lower voltage measured at sign than at the main power source.

Breaker Amperage
LED Signs will pull a certain amount of amps, depending on the sign type and configuration. The breaker sizes need to be sufficient for this amperage, or the breakers will trip when the sign exceeds the breaker’s amperage rating.

Loose Connections
Electrical connections must be tight to function correctly. Loose connections usually occur during the initial installation, or service work done on the system. Temperature changes can affect these connections causing the sign to work in warm weather, but not in cold weather.

  • Power can be measured on the incoming side of the terminal, but no power registers on the sign side.
  • Sign works in warm weather, but not cold.

Main Power Source
Sometimes power can be interrupted from the main source to the sign. This can be caused by a break in the line itself or an issue with the power panel at the building, or sign.

  • Breakers are tripped at the sign or building.
  • Sign is completely blank on both sides and no communication can be established.

208 VAC System
I decided to do a special section on this. A 208 Volt system is NOT the same as a 230 Volt system. In most cases you will have issues with an LED sign that is configured for 230 Volts, on a 208 Volt system. Depending on how the 208 service is connected, your sign may initially work, but start to have a variety of issues in the long run. I've seen systems that were displaying issues that didn’t logically seem to have anything to do with power, but immediately were fixed when the power was corrected to a 230 Volt system.

It’s usually a safe bet that power is the issue when you have an LED sign from a trusted source with issues that you are unable to fix using reasonable troubleshooting methods. Power issues can create a wide variety of symptoms and can be very challenging to recognize immediately. Always keep power in mind as you troubleshoot an LED sign system. If you find yourself saying, “this just doesn't make sense”, it’s time to check the power.


I hope this post has been informative and helpful. As usual, I welcome ALL constructive comments. Please feel free to comment and add anything I’ve missed, or additional tips you may have regarding this topic. Please visit for many other resources, white papers, and of course: Great looking LED Signs!

**All posts/thoughts/writings are strictly the viewpoint of me and me alone and do not reflect nor speak for Vantage LED’s beliefs, attitudes, thoughts, etc. unless specifically stated.

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