long strings

strangesparks

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I'm just getting started on automating my lights, but I've found that the long 250 led strings aren't working the way I'd expect.
the majority of the lights are only very dimly lit, and the end sections are bright.
the strings don't have any breaks, and work fine on the original psu.
my new PSU is rated for 500W, 24V DC, which should be able to supply the current needed, but the lights are only drawing 4mA, as opposed to the 36mA from the original supply. this current issue is the same direct from the supply or through the dmx.


so how can I force the lights to draw more current? or am I missing something?
 

scamper

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I agree with David, a little more information is required.
What are the lights from? If they are Bunnings or big W type lights, then they will need around 27v
Maybe power injection is needed.
Or maybe the wire you are using is too small.
 

AAH

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Most brick type power supplies have an adjustment range of +/- 10%. Winding the supply up to the maximum might improve things. Also a picture of the original power supply showing the details might help us out.
 

strangesparks

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OK. That's a bit of help. I'm surprised that the voltage could be the issue as the original PSUs/controllers drop well below the 24v mark when going through its fade.
These are the generic led strings from the warehouse or mitre 10. And seem to be the same found in any store, bunnings dick Smith etc. Just rebranded to suit
The light themselves are a mixture, some claim to be AC, some DC. But All will run on the DC coming from the original controller.
The controllers are all the same from Changzhou jutai electronic co. They all seem to work universally with any light string and controller combo. I'd attach a picture but can't see how at the moment.
 

David_AVD

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Light strings vary somewhat in the voltage used and whether the power supplies are AC or DC.

Getting the exact specs on the transformer for the strings you're talking about is crucial.

I think the only way we can move forward is to show a picture of the original transformer.

Use the "Attachments and other options" link just under the text box to add images from your PC.
 

i13

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The reason the original plugpacks drop below 24V is they probably just pulse very quickly. This causes less light output but most people can't see the very fast pulsing so the lights just appear dimmer. Whatever you're using to measure the voltage probably isn't keeping up.

It is really the current you need to measure to work out the correct voltage. 24V seems too low. A light set with a 24V AC plugpack will almost always need a higher DC voltage.
 

multicast

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i13 said:
The reason the original plugpacks drop below 24V is they probably just pulse very quickly. This causes less light output but most people can't see the very fast pulsing so the lights just appear dimmer. Whatever you're using to measure the voltage probably isn't keeping up.

It is really the current you need to measure to work out the correct voltage. 24V seems too low. A light set with a 24V AC plugpack will almost always need a higher DC voltage.




This is because AC voltages are normally "RMS" vlaue.. ( root-mean-square )... and DC values are absolute.. 24VAC( rms ) is 24 x square root of 2 = 24 x 1.41 = 33V Peak to Peak. If you rectify teh 24VAC you'll get about 30-32VDC. ( got to take into account some didoes )
 

AAH

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24VAC is actually 33V peak to centre or 66V peak to peak

http://www.learnabout-electronics.org/ac_theory/images/fig1-1.gif


multicast said:
i13 said:
The reason the original plugpacks drop below 24V is they probably just pulse very quickly. This causes less light output but most people can't see the very fast pulsing so the lights just appear dimmer. Whatever you're using to measure the voltage probably isn't keeping up.

It is really the current you need to measure to work out the correct voltage. 24V seems too low. A light set with a 24V AC plugpack will almost always need a higher DC voltage.




This is because AC voltages are normally "RMS" vlaue.. ( root-mean-square )... and DC values are absolute.. 24VAC( rms ) is 24 x square root of 2 = 24 x 1.41 = 33V Peak to Peak. If you rectify teh 24VAC you'll get about 30-32VDC. ( got to take into account some didoes )
 

strangesparks

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i13 said:

The reason the original plugpacks drop below 24V is they probably just pulse very quickly. This causes less light output but most people can't see the very fast pulsing so the lights just appear dimmer. Whatever you're using to measure the voltage probably isn't keeping up.

It is really the current you need to measure to work out the correct voltage. 24V seems too low. A light set with a 24V AC plugpack will almost always need a higher DC voltage.

None of the original supplies are giving any AC, so we can put that one to bed.

The original supplies are labelled as 31V. but now you mention the pulsating voltage it makes a lot more sense.
[font=verdana, arial, helvetica, sans-serif]My controller is rated at for a max of 24V, and passes whatever I put in straight through to the outputs. I could push the voltage up, but run the risk of damaging the controller?[/font]
As it stands I'm guessing that I'm up a creek without a paddle if the string doesn't respond the way I want?

Surely I'm not the first to try and use these longer strings on dmx? is there any suggestions as to how it could be achieved? someone mentioned voltage injection?
 

multicast

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Ok, you can have 11 points and I owe you a packet of tim-tams. ( althought we have superior biscusits this side of the tasman )... You are absolutely correct and I was just too quick on the answer.

AAH said:
24VAC is actually 33V peak to centre or 66V peak to peak

http://www.learnabout-electronics.org/ac_theory/images/fig1-1.gif


multicast said:
i13 said:
The reason the original plugpacks drop below 24V is they probably just pulse very quickly. This causes less light output but most people can't see the very fast pulsing so the lights just appear dimmer. Whatever you're using to measure the voltage probably isn't keeping up.

It is really the current you need to measure to work out the correct voltage. 24V seems too low. A light set with a 24V AC plugpack will almost always need a higher DC voltage.




This is because AC voltages are normally "RMS" vlaue.. ( root-mean-square )... and DC values are absolute.. 24VAC( rms ) is 24 x square root of 2 = 24 x 1.41 = 33V Peak to Peak. If you rectify teh 24VAC you'll get about 30-32VDC. ( got to take into account some didoes )
 

David_AVD

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Are there 2 wires or 3 wires between the controller box (or PSU if it's the integrated type) and the first LED ?

If only 2 wires, you're in for some pain.
 

strangesparks

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David_AVD said:
Are there 2 wires or 3 wires between the controller box (or PSU if it's the integrated type) and the first LED ?

If only 2 wires, you're in for some pain.

No they're all 3 wires.
 

i13

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What 24V controller are you trying to use? The only common one I can think of is the 27 channel one that Ray Wu sells. If this is the case then you'll be fine using it with up to 35V despite what the label on the PCB says.

You're very lucky about the three wires. Always watch out for that if you buy lights with an 8-function controller.
 

strangesparks

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i13 said:
What 24V controller are you trying to use? The only common one I can think of is the 27 channel one that Ray Wu sells. If this is the case then you'll be fine using it with up to 35V despite what the label on the PCB says.

You're very lucky about the three wires. Always watch out for that if you buy lights with an 8-function controller.
The controller is a 30 channel 12-24v from oasis technology co. I bought it on aliexpress. Apparently good for 2A a channel.
 
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