Power Infrastructure For LED Fixtures

Power Infrastructure For LED Fixtures

LED fixtures are now ubiquitous in every venue in Australia, be it a school, professional theatre or nightclub. We love LED fixtures because they are efficient light sources that allow multiple uses and dynamic colour mixing. However, as LED fixtures have been so rapidly thrust upon us and the technology has moved forward so quickly, our power infrastructure has been left behind in the dust. The entire way we think about power distribution as we go forward has to be radically redefined and updated. No longer is a dimmer the answer for every venue. As we move forward we must look at a hybrid solution of hot power, relays and dimmers to cope with our hybrid rigs of LED and conventional fixtures. Our solutions must be able to cope with any type of load on any circuit at any time. There are also a few major issues to consider when we move to a solid state solution, these include Inrush Current and Resting Power Draw.

The Correct Solution.
Specifying the "correct" solution is where this starts to get complicated, as with any new technology there are many schools of thought on the issue. In this article I will offer my opinion of what should be best practice for dealing with the venues of the present while also future proofing for the fixtures of the future.

One solution to move forward with power infrastructure is to implement a Dimmer and Bypass Relay per circuit. That is, every circuit in the venue can either be a dimmer, switch or full on power circuit at any time. This solution provides for the most adaptability and versatility in a venue because it means that no matter where you plug in your fixture you can provide any type of power. This solution can be implemented whether the venue is dimmer per circuit or involves a patch system. The relay bypass dimmer system allows you to create a truly hybrid rig, where you can employ any range of fixture be it LED, Tungsten, HMI to any position in a venue.

This is the most flexible solution but also requires management of each circuit and more importantly requires the right product with specific design features to counteract issues such as "ghost power" and true undistorted AC waveforms.

Why use a relay? Why can't I just leave my LED's on all the time?  
There are a couple of major reasons why using a relay with LEDs or Solid State lighting is very important. The first of these is an issue called Inrush Current. When a transformer or driver in an LED fixture fires up for the first time it can draw many times its usual power draw, this can be almost a tenfold increase. Although this extra draw is only for a very short amount of time, if you are trying to turn every fixture on at once by flipping a mains breaker and if your circuits are anywhere near load this could have a catastrophic effect. Below is an example of the effect of inrush current.

Inrush Current Effect

For this reason it is important to be able to switch on your LED fixtures in batches or one fixture at a time. A true relay system is the only way to reliably activate these fixtures remotely. It allows per circuit power up first time every time and guarantees to limit the effect of inrush current on the rest of your venue. 

The other reason for employing a relay per circuit is to counteract the effect of idle power draw. One of the big reasons touted for changing to LED is efficiency and sustainability, however the idle power draw of an LED fixture can very easily negate these effects. By saying the idle Power draw, I mean the power used by an LED fixture when it is sitting idle with no light coming out. When an LED fixture is idle it still has control circuitry, electronics, processors and fans whirring away drawing power. Compared to a traditional tungsten fixture that when idle draws no power whatsoever, the LED can quickly negate any efficiency high ground. Some LED fixtures can draw up to 20 or 30 watts when idle. Connecting every LED fixture to a relay allows you to remotely power off idle fixtures, therefore stopping their idle power draw.

Two relays are better than one.
When using a dimmer bypass system it is important to use a product with well designed circuitry that can provide the correct power every time and also minimise human error. We have all probably experienced the time when we plug a moving light into a dimmer and the leak of "ghost power" causes the fixture to attempt to start up, this can cause damage to a fixtures circuitry. In a dimmer/relay per circuit system we need to ensure that this can't happen. For this reason, in the Jands HPC12 we employ a unique bottom relay or isolate relay to entirely isolate the output from the dimmer circuitry.

Isolate Relay
Isolate RelayWhen the dimmer is left at zero for more than a minute or the circuit is set to a Switch or Full On circuit, the isolate relay automatically opens. This creates an open circuit to the dimmer circuitry and from the diagram above you can see that the dimmer is completely isolated from the circuit's output, this means that the circuit can never leak any "ghost power" out the output. More importantly when the circuit is set to a True Mains Power circuit it means that absolutely no mains is routed through the chokes and ensures reliable clean mains is routed to the output.

Bypass Relay
The bypass relay on every circuit bypasses all dimming circuitry to allow the HPC to give true clean mains power out of every dimmer outlet. The relay fully bypasses the choke to ensure the true un-distorted AC wave is distributed to every circuit, there is no attempt to rebuild a distorted wave, just a straight through connection from input to output. The relay's action is fully user configurable, and allows the circuit to be turned off remotely from the console via DMX or via RDM. 

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David Haddock

A dmx controlled power switcher (no dimming) would be a good way to avoid problems like this. You guys should be able to make one easy !

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