LED Driver Question

[GrahamW]

Novice here. I am looking to install (a lot of powerful) LED lights in my kitchen and I want to understand the implications of putting PSUs in my lighting circuit.

I currently have 15 halolite tube lights (16W each). That's 240W @ 240V (so one amp of current, right ?)

I'm thinking about bright LED strips which are 21W per metre. About 10m should be plenty - 210W in total.

Seems quite similar. But the ampage of these 12V strips is 1.75A per metre ... so 17.5A in total ! Now I'm more than a little wary of putting "so much current" through a lighting circuit !

I'll split the installation into two halves - with a 120W PSU (or "LED driver") on each. Each PSU talks about "10 Amps 240v to 12V DC Transformer (120 Watts)".

So each puts out 10A @ 12V creating 120W of power ... but what does it draw from the input side ? Assuming no losses, it must need 120W from a 240V supply which would be 0.5A for each driver, yes ?

So is it safe to use two of these PSUs in my lighting circuit and will they only draw a total of 1A (which is only the same as two of the old 60W light bulbs) ?





Cheers

Graham

 

[telectrix]

about right. the current @ 12V is 20 x that at 240V. that's why you need larger CSA cables on the 12V side of driver/transformer.

 

[i=p/u]

Your current draw will be on the 230v so yes same as two light bulbs as for drivers they have a limit of say 120w maybe use upto 80w on each and not use them at full load or under load.

as for your psu/ drivers they might have a max distance like in normal transformers

 

[GrahamW]

that's why you need larger CSA cables on the 12V side of driver/transformer.

So do I need to use special cable for the links from the PSU to dimmer unit and then to my splitter ? I was going to connect 3-4 strips to each PSU (in parallel) so each of those would only carry a max of 1.75A.

 

[GrahamW]

as for your psu/ drivers they might have a max distance like in normal transformers

What sort of distance ? I can see that some strips will be right next to the PSU, but some might me 2-3 meters away.

 

[infinity]

The current wont be as high I the 230v side! So cable will be fine! Ohms law

 

[i=p/u]

But he's looking to extend the 12v side... Which depends on transformers / driver used

 

[i=p/u]

1v will light 100w lightbulb on 25mm cable

 

[telectrix]

1v will light 100w lightbulb on 25mm cable

you been on the bushmills?

 

[GrahamW]

But he's looking to extend the 12v side... Which depends on transformers / driver used

Is there a rule of thumb as to how far I can run the wiring between the transformer and LED strip ?

i.e. is there a "at 12V you lose x Watts/Volts every y metres" kind of law ? I'll be using pretty normal twin-core mains cable.

I think I'll keep a REALLY short link between transformer and dimmer, then another short link to my splitter ... and then run multiple feeds to the LED strips (@ "only" 1.75A each). That way, the longer cable runs won't have the bigger currents in them.