Power Controllers and LED Light Systems

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I’m seeing more and more customers with LED light units, and often get questions about whether my Smart Power Controllers work with them. Here are some technical notes about using LED light systems with the Light Counter system.

Background

Older UV light systems tend to use either fluorescent tubes or “hot” bulbs. Fluorescent tubes are cheap, low power and long lasting, but relatively slow. Hot bulbs are very bright, but tend to blow up if you switch them off then on again.

LED systems are a modern alternative that offer good light coverage and much higher power. However, whilst “much higher power” is great for printers, it is problematic for electrical control gear.

The Engineering Problems

When designing electrical control gear, you have three main problems to solve — steady state load, inrush current and heat.

Steady state load: This is the power drawn by the unit when its lights are on. My fluorescent tube system draws 4-5 amps, which is less than many household vacuum cleaners. By contrast, large LED systems can draw two or three times that.

Inrush current: All lighting systems suck in a ‘spike’ of energy when they switch on. This is called inrush current. The spike only lasts a few milliseconds, but that can be sufficient to damage electrical equipment. Inrush current is difficult to measure without specialist equipment. Fluorescent tubes typically have an inrush current of between 2x and 10x their steady state. LED systems can have an inrush current 100x their steady state, but this very much depends on their design.

Heat: All electrical systems generate heat. Excessive heat can damage electrical equipment and worst case becomes a fire risk.

Light Counter Power Controllers

The Light Counter Smart Power Controllers work by switching the mains electricity supply to the light unit. This is a simple, effective and well-proven solution, with two consequences:

  1. The power controller doesn’t need complex control gear inside, which is a good thing because that keeps it affordable for most photographers (incidentally, this is why they don’t work with Nuarcs)
  2. All the power going to the lights also goes through the power controller, which is not such a good thing when dealing with very high power light units

For a long time now, I have stocked two versions of my power controllers: “standard” and “professional”. The standard version has proven to be an excellent solution for most people, but it struggles with high power LED systems. Due to the increasing number of LED light systems, I have decided to withdraw the standard version from sale.

The professional power controller contains more expensive, but higher specification, components and is hardened for higher loads. It is rated for 10 amps steady state, and up to 800 amps of inrush current. This is sufficient for 95% of today’s LED light systems.

“Will the power controller work with my lights?”

The most common question I get from customers is, “Will the power controller work with my lights?” And, “Yes,” is the simple answer for most people. Here’s a guide to help with your decision.

The key question is: what is your light unit’s steady state current? If it is 10 amps or less, then the power controller will be fine (even for LEDs). You don’t need to worry about any of the things that I write next.

Things get tricky if your light unit pulls in more than 10 amps. In this situation you have two options —

The right thing to do is ask an electrician to install secondary control gear for your lights. For example, you could have the power controller switch on a cheap industrial relay, which in turn switches on the light unit.

Alternatively, if your lights require only a little more than 10 amps, then you could simply insert a higher value fuse in the power controller. At this point I have to say clearly: if you do this then it is at your own risk and is not covered by the warranty.

The power controller’s internal components are rated at 16 amps steady state. So, for example a 12-14 amp light unit would work if you use a 15 amp fuse. They are rated at 800 amps of inrush current, which could also be OK. (The problem here is that you won’t know that the device is being damaged by excessive inrush current until it’s too late. The symptom to look out for is the power controller failing to switch off at the end of an exposure. This happens when its internal relay contacts fuse together because of excessive inrush current. This damage is not covered by the warranty.)

Heat is the remaining factor to be concerned about. All electric circuits generate heat when they are powered on. Excessive heat can damage the device and in an extreme situation becomes a fire risk. For short exposures with a 12-14 amp light unit, this is unlikely to be a problem, but but I’m not going to guarantee it because I don’t want liability in case New York burns to the ground because someone left their UV light unit switched on — so this would be at your risk.

Do You Have Any Questions?

If you have any questions then please don’t hesitate to reach out to me. Like all engineering, high power light units are a solvable problem, and I’m happy to help.