LED Sign Tech & Spec: Providing Correct Power Voltage to LED Signs and Why 120 VAC and 240 VAC are Both Important

- Scott Hofheins

Since we're on the subject of power (see Deacons Post), I thought I would write a little bit about Voltage, Amperage, how they affect LED signs, and why it’s important to supply the correct voltage. I will try not to get too technical, but stay clear and straightforward. 


What is Voltage and Amperage?
To keep it simple, I’ll explain power by using a water system filled with sand particles as an analogy.

• Voltage: How strong the “water pump” is pushing the electricity through the system. The water pump is consistent, and it’s pushing force doesn't change much (+/- 10%). If you capped the end of the “pipe” (flip the switch off) the voltage level would never go above the strength of the “water pump”. Typical outlets here in the U.S. supply 120 Volts and large appliance outlets (clothes dryer) supply 240 Volts.

• Amperage (Electrical Current): How fast the water is being pulled through the system. This “flow rate” is measured in Amps and will vary depending on the devices connected to the system. Signs can pull 20 -100+ Amps, and your smart-phone charger usually pulls only .5 - 2.1 Amps. Most residential outlets are rated for 10-15 Amps.

• Wire Size: How big the water line is. The sand in the water will cause friction, generating heat. The faster the “flow rate” the the larger the wire size needs to be to protect the line from overheating.

• Electrical Breakers: These are like emergency shut off valves. If the line does overheat, these valves immediately break the connection completely. They do this at specific Amperage levels depending on the breaker. The main breaker for your home is typically 100 amps, broken down into smaller breakers like 20, 30 or 40 Amps that connected to specific areas of a house.

How do these items affect LED signs?
LED signs are usually configured for 120 Volts AC (Alternating Current) or 240 Volts AC. These are standard voltages for most commercial and residential systems.The lower the voltage the faster the device has to “pull” the power. A sign configured for 120 Volts will pull about double the amperage when compared to the same sign at 240 Volts.

Smaller LED signs are usually configured for 120 VAC. This is because 120 VAC is more common, and is usually already supplied at an existing sign site. The larger amperage draw isn’t usually enough to justify pulling a new 240 VAC circuit to the site. Most signs in this category will pull 10 - 40 Amps, depending on the size.

As they get bigger, LED signs will start to pull more Amperage becoming less efficient. More amperage means a larger electric bill. So rather than using a 120 VAC sign that pulls 80 Amps per side, you will use a 240 VAC system that only pulls 40 Amps per side.

Why not just connect 240 VAC to a sign configured for 120 VAC to save energy, or 120 VAC to a 240 VAC sign?

• Amperage, Breaker Size, and Wire Size: As we discussed earlier, the amperage draw is directly related to the voltage. If your system was built to support a 240 VAC sign that pulled 30 Amps, and you installed the same sign configured for 120 VAC, the amperage would double to 60 Amps. This will affect both your Wire Size and Breaker Size. If you only account for a larger breaker size, you could start an electrical fire at 40-50 Amps when the wire overheats because the larger breaker will not “trip” until 60 Amps.

• Component Damage or Inefficiency: LED signs have many different electronic components. Some of these like the power supplies and cooling fans take AC (Alternating Current). Other components like the LED modules and video boards use DC (Direct Current). The power supplies are responsible for this AC to DC conversion (again, see Deacons Post). If you supply the wrong AC power, you can affect the other components in the system with mixed results.

• Power Supplies: Quality manufacturers use “Auto Switching” power supplies that will output a solid DC current within a range of AC voltage (120 - 240). This might save your power supplies from damage due to incorrect voltage, but the rest of the system can still suffer. However, the damage is much worse if the manufacturer does not use Auto Switching supplies. As soon as you supply the wrong power, many of them will burn out completely.

• Cooling/Exhaust Fans: Most cooling fans in an LED sign are connected directly to AC power. This means that their rotational speed is directly related to the alternating “cycles” in AC power. A cooling fan designed for 120 VAC that is connected directly to 240 VAC may blow completely. Conversely, if a fan designed for 240 VAC is connected to 120 VAC it may blow, or turn much slower causing the sign to overheat.

• Other Components: If the power supplies blow, they can surge the DC power for other components causing damage. If they don’t blow (if you supplied a lower AC voltage) they will sometimes provide a corresponding lower DC voltage. This will cause long term damage to the components and they will fail in variable degrees over time.

Why can’t I connect Three Phase 208 VAC to my 120 VAC or 240 VAC Sign?

I won’t get into the details, but unless you pay for a very custom build LED signs will only be configured for Single Phase Power. You will have issues if you connect directly to Three Phase power. Don’t Do It.

Can I connect to Single Phase 208 VAC?

I do not recommend this either. LED signs are more sensitive to voltage than a clothes dryer or refrigerator that operate just fine in the 208 range. An LED sign might work initially, but you run the risk of long term component damage due to under-voltage. You would also see poor performance of any AC direct components like cooling fans.

If the LED sign is configured for 120 VAC, the safe operating range is typically  110-120 VAC. If the sign is configured for 240 VAC, the safe range is usually 220 - 240 VAC.

The bottom line is: Voltage Matters.  Now (hopefully) you know why.

-SH




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 www.vantageled.com 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.

Power Cost of LED Displays

- Mike Prongue 

Many very technical people in the Electronic Message Center (EMC) industry, those who are licensed in electrical and in state construction regulations, look the other way and suddenly seem to want to change the subject when this innocent question is asked by a curious customer:

“What will this cost me to run?”

There is no reason to panic! And, better still, this question is a buying signal. If the customer has gotten this far into their evaluation of a possible EMC for their business, now is not the time to "freeze up". A great reply to this question may seal the deal for you.

It’s a very simple question to answer and you can start by calling your power company, or searching online for their price per kilowatt of power. If you don’t even want to do that, use the average of 10 cents per kilowatt ($.10).

Next determine the power consumption of the EMC in watts. This information has been provided by the manufacturer. If you do not have the watt specification then you will have the amperage draw of the EMC.

Remember that Watts = Amps x Voltage. So if you have an EMC rated at 10 amps, and it is installed in a 110 volt service, you have 10 (amps) x 110 (volts) or 1100 watts of power consumption (per hour).

1100 watts of power is 1.1 kilo Watts of power, of course kilo means “thousand”. We already determined the cost of power was  five cents per kilowatt.

If the customer runs the display non-stop, at peak power, displaying all lamps all of the time for24 hours per day, then it will cost approximately:

1.1 (kilowatts)   x   .10 (cost per kilowatt)  x   24 hours   =   $2.62* per day.

If it is a double-sided EMC, then the cost would double to $5.24 per day if the EMC ran at maximum output, all the time, no slide transitions, no interruptions, fully illuminated.

Simply because no EMC, in use by a customer, runs at maximum output all the time, you should use an very realistic percentage of max power when estimating average power consumption-- 30% of max. Just tell your customer to expect about a 1/3rd of maximum cost- even more affordable - $5.24 x .30  =  $1.58* per day!

This is a great investment. What other form of advertising only costs  $1.58 per day for thousands of exposures to thousands of customers (driving by)? Now you can share this great advertising deal with your customers- head held high, ready to impress!

Now close that sale!

* Always check with your local power company for peak/ off-peak rates, and understand that this article is a general statement on the subject and not specific to your project.

**Note 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.

The Future's so bright: Issues with "bright" LEDs for EMCs

-Deacon Wardlow
NITs, Lumens, Flux, Foot Candles*, however light output is tested you have to be sure the reported measurement is giving you the complete story. The output on your EMC (Electronic Message Center) may not be what you think it is. Overdriving LEDs still occurs in the industry because people believe brighter is better. When you look at the brightness rating on a system, be sure you get what you’re paying for.

The practice of overdriving LEDs has been around as long as LEDs themselves. An LED has a given rating for performance. Go under the rating for an LED and you’ll have mid to fair performance. At optimal rated driving (current passed through the LED) an LED will shine its brightest for the longest measure of time before it depreciates below useful levels. When someone overdrives the LED, they cause more current to flow through the LED.

LEDs work via PWM (pulse width modulation). The faster an LED pulses, the brighter it appears. The slower the pulse, the dimmer the LED appears. By increasing current to the LED, it’s overdriven and made to appear/test at higher levels than normal.

More current = more/brighter pulses = brighter LEDs. Unfortunately more current = more heat = faster degradation of the LED = shorter lifespan for the LED sign. Here’s a short example of the Overdrive factor and how much the lifespan of an LED is reduced:

While a manufacturer may claim higher brightness, be wary on how they obtain that brightness. If in doubt, ask them to name the manufacturer of the LED and go direct to the LED manufacturer to check brightness capability claims. A reputable manufacturer should be able to show proof the LEDs are all within rated ranges and not being overdriven and they should have no qualms with you verifying the information yourself. Don’t let claims of high brightness on an EMC blind you to the truth.

*For a deeper description of the abbreviations and terms, please check the online EMC glossary here.If you like it, please drop a thank you email to me (and the team at Vantage LED) for the info! Also read about NIT Values and Measurements here.

**Always feel free to comment here and/or email me directly with requests at deacon@vantageled.com. Vantage LED has white paper resources and more educational material on the website (http://www.vantageled.com), please check it out when you have a moment.

***Note 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.

Silent LED Message Center Killers: Power

-Deacon Wardlow

   

Improper power can damage the longevity and performance of your LED message center. Lightning strikes can instantly destroy expensive electronics without warning. In other cases, brown outs, under/over voltage and current spikes caused by excessive power demand can also damage electronics. The electrical grid that delivers power is subject to disturbances and potential failure.

Top 5 Power issues:

· Voltage Spike: An instantaneous increase in voltage from 300 to 6000 volts (normal is 120 Volts) caused by lightning or grid fault

· Over Voltage: a longer-term event caused by a large load instantaneously taken off the grid causing voltage to rise above 138 volts

· Under Voltage (Brownout): Too much load on the power grid resulting in voltage decreases from 120 volts to below 90 volts

· Power Outage: Zero voltage lasting for 2 seconds to several hours

· Voltage Sag: Caused by a large load placed on the grid resulting in delivery of less than 100 volts for up to 2 seconds

All grid disturbances can potentially damage sensitive electronic components. The most common and under-reported grid disturbances are Voltage Sag and under voltage events. In some cases, Voltage Sag occurs 30 to 100 times per year. The Under Voltage event is similar to a Voltage Sag, but last longer – sometimes for hours, days, and weeks or even years before the inevitable long-term damage is visible and the problem isolated to under power on the system. Voltage Spikes can also cause serious damage, including fire, but are less common and damage can usually be avoided with surge suppressors which should be a standard component for a reliable manufacturer of LED message centers.

Under Voltage and Voltage Sag events in the power grid cause the most serious damage because they chip away at the integrity of the equipment with each event and there can be hundreds of events in a year. When a Voltage Sag or Under Voltage event occurs, it is also followed by a current surge or current inrush when the proper voltage is restored. The constant fluctuation of power will shorten the life span and performance of the system.

Protect your business and your investment. Any installation of an LED message center should include power metering which most electricians and LED sign dealers should be able to do. This one time metering will save you lost business when a system fails years early due to consistent under voltage or other power issues which could have been caught at the time of initial installation.

The power company won’t step up and do anything until you have proof positive there’s a problem. By monitoring a new installation over a weekend or (even better) a week, you’ll know if the power is good or if there’s a problem. You can be sure you, your brand and your reputation (along with the investment in the LED message center) will be safe for the long haul.

*Always feel free to comment here and/or email me directly with requests at deacon@vantageled.com. Vantage LED has white paper resources and more educational material on the website (http://www.vantageled.com), please check it out when you have a moment. Advertisements/promotion for your business and inappropriate comments will be deleted.. Thank you!

**Note 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.