Dead Sections In LED Strings

[ChevyChase]

Am I just unlucky or does anyone else suffer with "dead" sections in some of their LED strings.  I`m guessing that the problem may be due to moisture ingress?  Any thoughts?

[sandy123]

If you bought the strings from somewhere else, other than Synchrolight, chances are they are designed to work from an AC Transformer. Half of the lights on the string will light on one half cycle and the other half will light on the second half cycle. Check the packaging and the transformer to state they are DC.
If the lights were/are DC supplied, then it seems could be the in-line resistor that has burned out for that particular leg of the circuit (6, 8 or maybe 10 LEDs are out on that leg).
If that's the case, it's not moisture as that would affect the whole circuit, not just a few LEDs on the string. Wear & Tear, or feeding a small number of lights from the 24v Transformer (rated at 5 Amps). Voltage will be a lot higher than 24v if you are only drawing a few mAmps or Amps.
Hope that helps mate

[ChevyChase]

Thanks. All my LED strings are DC supplied and by syncrolight. I can`t think it`s wear and tear as 2 of the strings are only a year old and one of the strings is new this year. I`ve got at least 1000 leds running off each transformer too. I new one string wasn`t working 100% before I put them up this year but now there`s another two with sections out.

I was thinking weather as it`s been extremely wet and windy lately but ?

[sandy123]

200 LED string draws approx. 600mA according to the website. 100 LED strings are about 250mA, so 1000 LEDs will draw about 2.5 to 3Amps in total. If you're using the 24v 5Amp transformers to supply these circuits, the actual voltage will be above 24v. Transformer is rated at 24v when it is supplying 5Amps.
You could try taking the string down and laying it on a radiator for a few hours to see if it dries out any moisture. Another way of checking them is to identify the leg that has the duff LEDs on it and looking at each unlit LED to see if there's a slight 'lump' on the side just underneath the individual LED. If so, this will be the in-line resistor for that leg and if there's signs of overheating at that spot, then you know it's the resistor that's burned out.
When I use my 24v Transformer, I try to load it up to as close as I can to 5 Amps to ensure the voltage across my LEDs is 24v. More voltage equals more current, which will eventually burn out the resistors and/or LEDs themselves. On 'no load' the transformer kicks out over 30v.
Sorry if this reply gives you a bigger headache
Regards
Sandy

[ChevyChase]

Many thanks for your help. I`ll take a closer look and do some maths!

[ChevyChase]

So it turns out that I`ve got 760 LEDs running from one 2.5A transformer. I`ve added this up to a total of 1950mA. On my other 5A transformer I`ve got 1300LEDs which add up to 3750mA.

Apologies if I`m being a bit thick. I did electronics at school all them years ago. Don't the controllers just give a constant voltage and the amount of power drawn varies?

I`ve also noticed that some parts of the strings flicker next to the dead sections. I`m a bit loathed to bring them in to try and dry them out until after Christmas now. It`s just a bit frustrating as I had problems with a set last year which syncrolight kindly replaced but then the replacement got dead sections in a few weeks later. This year I`ve got an additional 2 sets playing up after only being out a week or so.

[sandy123]

They are unregulated supplies. Voltage varies with the current drawn. 24v is outlet voltage when the current drawn is at the rated 2.5, or 5Amps.
No load voltage is approx. 34volts (ac) and this drops towards the 24v when the load is increased. If you've got the lights on a sequence, then they will only draw the current for the lights that are on at any one time. e.g 100 LEDs on will only draw approximately 250mA from the transformer and the supply voltage will rise momentarily until other circuits are on (hope that makes sense!!?)
I use a mixture of regulated and unregulated supplies when I put up my displays, depending on how I've mixed the light strings, and what sort of sequence I'm running. I've got a video of this year's display, but no music and most of the video is concentrated on digital projection (to show relatives in Scotland), I've used regulated and unregulated supplies. If you want to see it, I'll post it and try giving you some pointers as to what I've used

[ChevyChase]

Sure, would like to take a look.

[sandy123]

I'll start a new thread, incase this one gets hijacked mate

[Craig]

As Sandy correctly explains, the power supplies must be loaded correctly to ensure good LED lifespan. The LED strings are made with tolerances for the larger power supplies, but these tolerances do vary between colours and batches. Individual strings/channels should only be left on for very short periods as part of a light show. If strings are left on constant for longer periods, all or multiple channels should be turned on to ensure correct loading of the power supply. The power supplies should be loaded to 80%, which equates to around 1600 leds on a 5 Amp power supply. 

If the power supply is not loaded sufficiently you can try reducing the brightness of the lights in your show or try the updated firmware and Device Manager below which allows limits to be set on the channels of the controller to help protect the light strings. Download the V1.6 firmware onto the controller and in the Device Manager set the brightness limit so the LEDs are a good brightness without being excessively bright.

   

  DeviceManagerWithOutputLimits.zip (Size: 256.92 KB / Downloads: 7)