15 May 2017

Three Biggest LED Wiring Mistakes And How To Fix Them

Image one: the LED wiring inside of this channel letter has been split.
Image two: burnt LED module.
Image three: it seems that the power supply unit is under strain, causing the power to fade.
Image four: specification sheet.

LED's are versatile, giving more options to clients in terms of colour, spread of light, brightness, aesthetics and design. However, there are things you should consider when wiring them. Our tips will ensure that you get an evenly illuminated sign with no hot spots.

1. Incorrect Wiring

Don't split the power. The biggest mistake that installers make is that they wire the LED’s incorrectly due to lack of knowledge and experience. In image one, the installers have split the one line to two lines as parallel. This is incorrect, and bridging the wires will ensure that there is not enough power leading through wires into the modules.

When connecting the LED's in a form of a letter, for example, a 'Y', it's not advisable to connect the wires from the middle. You need to connect the wires separately so that all the LED's are connected in a series. If you were to connect from the middle, over time, the current will fade and you'll get a drop off in current because of too much resistance on the join.

Don't switch the input and output of the transformer. For example, if you have a 220V power supply, there will be 220V coming out on the left hand side, and a 12V DC power supply coming out the right end. What we often find is that installers swop them around and then when they connect the 12V DC, they blow the power supply.

Always check that the cable you use is adequate to carry the existing load as per the original design. The longer the wire, the more power you lose over distance. Depending on the module, parallel connections can also light up without voltage drop. However, we recommend a series connection.

Useful Checklist:
• Know your LED's specifications.
• Check if the correct wire thickness has been used.
• See if all connections are properly connected and sealed.

2. Too Many Modules Connected To One Wire

Each LED has a maximum quantity of connections, don't exceed this (see image two). If you do, then the colour will be dimmed or flicker, resulting in a lack of power. It is very important to remember that the more modules you have, the more power you need running through your wire. Also keep in mind that more power needs thicker wiring.

Things to take into consideration include the type of populating required, for example 24V or 12V, with 12V being the most popular. 12V fittings need the correct transformer depending on your number of LED's in each module's wattage.

Useful Checklist:
• See that LED's are wired with no more than 50 modules in a series and the high power modules have a maximum of 20 in a series.
• Check the specification from your supplier on the maximum quantity that can be connected in one series of wires.

3. Incorrect Calculation

Mark ups are tight, and in an effort to reduce costs, companies will often try and decrease the amount of LED's used, without taking into account the 30% safety factor. This can cost your company in the long run as you'll end up with half-lit signs (see image three) or signs that don't light up at all, ensuring that you will lose clients and your good reputation. A flickering sign is a major indication that there is not enough power and that there is an incorrect calculation. Check the switching mode power supply (SMPS) efficiency.

Some believe that 150 Watts is 150 Watts. However, this is not true for a 12V output. As you can see in the specification sheet (image four) it is written that the rated power is 120 Watts (12V x 10A = 120 Watts). So it is extremely important to know the specifications in order to present good quality work.

The Street Warrior LED for example has a 160 degree lens with three LED's per module. The LED also runs at 1.2 Watts. So the maximum number of LED's you're going to run in one row will be 50 units.

When working out the power supply needed to run these LED's, you need to add in the 30% safety factor so that with the 1.2 Watts, you're actually going to be running at 1.56 Watts and you can work out the number of modules that will give the total wattage needed to run the LED's.

Additional Tips

When starting a new job, ask yourself the following:
• What is the depth of the return of the sign or light box? If it is less than 80mm, it will be too slim and you won’t be able to use LED’s.
• Will the sign be located indoors or outdoors?
• What is the amount and size of LED’s that will be required?
• What is the client’s warranty expectations for long-term LED’s?

How Will You Go About Wiring The Sign?

Consult with your client to assess their requirements and whether LED's are suitable for their project. Then discuss the various features and benefits to ensure they meet these requirements. By going through this process, you'll ensure that your clients are extremely satisfied with the outcome of the signage quality. Demonstrate examples of LED's in operation during the initial

Determine the distance from the LED’s to the Power Supply Unit (PSU) and the distance to the main power supply to the PSU. The greater the distance, the thicker the cable will need to be to keep the current constant. Over a large distance, the current will drop and can cause a failure in the PSU. For a shorter distance, a normal cable can be used.

See the full article in the March/April edition of Sign Africa Journal. Look out for part two of this feature in the next magazine.

Maizey Plastics and Exion Corporation

Maizey Plastics and Exion Corporation

Authors | and

Maizey Plastics is the largest, independently owned supplier of semi-finished thermoplastic materials in Southern Africa. Established in 2013, Exion caters to the signage industry throughout Southern Africa.


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