Calculating volt drop on 24v, supplying LED lights.

[HappyHippyDad]

I'm getting a little confused about volt drop and 24v.
I want to fit an LED strip light. 8m of lights 7w/m.
It would be easier to have the 24v driver approx 10m from the beginning of the strip of the LED strip.
I'm not sure where to start to know if this will work without any effect on the lights due to volt drop.
Is it 18m x 2.3A x 44 = 1.76v?

The 2.3A is 56w/24v
The 44 is based on 1mm

I'm getting a bit mixed up between 24v and 230v.

Is this 1.76v correct and is this taken off the 24v? If so, how do I know how much VD is ok for these lights? Is there a standard allowable VD as with 230v?

Cheers all.

 

[newfutile]

The voltage does not come into it, its just ohms law a current flowing though a resistance.
the manufactures are the only ones who will know minimum voltage , if in doubt use thicker cable or parallel (like a ring) or even feed from the centre.

 

[Strima]

Have the manufacturers given any voltage tolerances for the LEDs? Normally they would state maximum length of tape per driver.

 

[Zerax]

As above... manufacturers instructions to start off with. Is the driver CC or CV ? Don't forget that with DC it's a round trip length you need for any voltage drop calculations. There are various online calculators. Like this one... DC Cable Sizing Tool - Use The Correct Sized Cables - Free Calculator - https://www.solar-wind.co.uk/info/dc-cable-wire-sizing-tool-low-voltage-drop-calculator

 

[HappyHippyDad]

Thanks for the replys so far.
I can't feed it like a ring, or from the centre, due to constraints.
The manufacturer states 10m can be accomadated, but it gives no specification on acceptable voltage lose.
I think I need to place the driver closer.

But, I will push my luck and ask if anyone thinks this will work, I realise you will say it depends on MI, but I'm asking if anyone has done it and it was fine....

24v driver.
10m of 2.5mm or 4mm cable from driver to beginning of tape. 8m of tape. 2.3A current.

 

[pirate]

Frankly, I think it will be fine, what you suggested. However, why not just connect 10m of 2.5mm to the driver output and measure what voltage you get at the end?

 

[HappyHippyDad]

Frankly, I think it will be fine, what you suggested. However, why not just connect 10m of 2.5mm to the driver output and measure what voltage you get at the end?

I could do that, but I then need to know the tolerance levels (in terms of VD) of the actual LED strip and they don't give that information, at least I can't find it on any spec.

I could easily place the driver closer, however there is another LED strip on the other side of the room and I am trying to supply both sets of 8m strips with the same driver. The reason for this is that they will be colour changing and dimmable with a remote. I have not installed this scenario before and assumed that each set of lights (on a different driver) would have a separate remote, and I don't want the customer to have to use 2 remotes. Could both set of striplights be controlled with the same remote if using 2 separate drivers?

 

[pirate]

I take your point, but if you found that the VD was negligible with 2.5mm or if you had to go to 4mm. then you wouldn't have to worry at the feed-in side. I suspect, from my experience of 12V and 24V electrics on boats, that the VD will be negligible in the scenario you depict.

 

[HappyHippyDad]

I take your point, but if you found that the VD was negligible with 2.5mm or if you had to go to 4mm. then you wouldn't have to worry at the feed-in side. I suspect, from my experience of 12V and 24V electrics on boats, that the VD will be negligible in the scenario you depict.

In that case Pirate it would be good to pick your brains about what is 'negligible'?

Are my calculations in the opening post correct? If so, is 1.76v negligible?

If 1.76v is too much, I could use 1.5mm or 2.5mm cable instead, getting a VD of 1.2V and 0.75V respectively, this is assuming my calculations are right for 24V.

 

[Pretty Mouth]

Regs for ELV lighting give us a 5% VD allowance, so 1.2V for 24V lighting.

Each metre of LED tape will have a VD: tape closest to the origin will be carrying the most current, so will have the greatest VD per m, and tape furthest from the origin carries the least current, so will have the lowest VD/m. This could be calculated to a reasonable degree of accuracy if we knew the CSA of the conductors running the length of the tape. But we don't, so we cant ?

I've written a VD spreadsheet, which is pretty handy when working out VD for ELV. Playing around with the numbers for the tape you have (7W/m), if 10m of tape has the full 1.2V drop, then 8m would have a drop of ~0.8V. This would allow a drop of 0.4V for the 10m cable, which could be achieved by using 2.5mm cable.

Obviously, the above makes a couple of assumptions which we just don't know, so don't take it too seriously. In this case, trial and error is the only way!