Can I use A 12v transformer to power 30w led lighting

[underdog]

I know an led driver is normally required simlpy because led's dont draw enough power for a standard transformer to work, but if the total power of the led is within the VA rating of the 12v transformer will this be suitable?

20-60va 12v transformer to power 36w led lighting box.

I cant see any problems here but thought its worth asking as the wholesalers have led drivers up to 50watts that cost a furtune!

 

[i=p/u]

but is the leds rated at 230 or 12v

 

[underdog]

sorry should of stated its 12v controller which then supplys the actual led with 8.?v if i remember correctly but it needs a 12v supply to the controller! bit strange as i would of thought the controller would of have a 240v supply and transform the voltage"

 

[Marvo]

More details about the lighting box would be needed to answer this. I would be cautious because Led's that have no drivers require a DC supply, a standard lighting transformer output isn't rectified so it's AC.

 

[Golden_Boy]

More details about the lighting box would be needed to answer this. I would be cautious because Led's that have no drivers require a DC supply, a standard lighting transformer output isn't rectified so it's AC.

Does the "diode" action not mean they will work from an AC Supply???

 

[underdog]

I havnt got the lighting box or manual with me atm but from what i red today, the controller drives the led's, the controller requires 12v supply. controller has 12v input 8.?v output to the led's.

unless your powering the leds direct you need to establish the correct voltage required and use resistors to achieve voltage.

most led devices has a driver, which just needs a 12v supply.

an example would be swapping 30w mr16's with 5w leds, the original transformer would be underpowered, so a lower rated transformer would be fitted which is also known as an led transormer/driver. as most transformers are designed for halogen theres no need to power low loads, so they make one just for low loads....

have i got the right end of the stick?

 

[Marvo]

Does the "diode" action not mean they will work from an AC Supply???

In general it's not a good idea, if the half cycle of the AC which is incorrect polarity exceeds the breakdown voltage of the diode junction then it's permanently damaged.

There are newer generation LED's that can be driven directly with an AC waveform but half of the LED illuminates on one half cycle and the other half illuminates on the other half cycle. It's technically two LED's rolled into one. They use some clever junction biasing technique to alternate the supply to two different diode junctions, I'm not sure exactly how the wizardry works.

I used to keep up with the latest developments and techniques through journals and magazines but it's an industry that's moving so fast nowadays I've fallen way behind. From a practical point of view I would carefully scrutinise the manufacturers instructions or datasheets on a case by case basis with problems like this.

 

[Marvo]

an example would be swapping 30w mr16's with 5w leds, the original transformer would be underpowered, so a lower rated transformer would be fitted which is also known as an led transormer/driver. as most transformers are designed for halogen theres no need to power low loads, so they make one just for low loads....

have i got the right end of the stick?

With MR16 LED lamps they have a built-in driver, or a least a series resistor as well as the separate driver/transformer. The on-board driver reduces the voltage further and also rectifies it.

 

[underdog]

Basically if your running LEDs from what I've researched, your going to need a dc supply, which is the only difference between a 50va 12v transformer & a 50va 12v led driver!

I did actually try with a normal tranny and they didn't work at all, works brilliant with the dc supply!

 

[Marvo]

Basically if your running LEDs from what I've researched, your going to need a dc supply, which is the only difference between a 50va 12v transformer & a 50va 12v led driver!

That's pretty much the bottom line, the confusion always comes in deciding if the LED lamp or array has a built-in driver which means it can be supplied directly with AC because the onboard driver rectifies the supply.

I did actually try with a normal tranny and they didn't work at all, works brilliant with the dc supply!

Glad to hear it's all working and that the AC supply you tried didn't destroy anything.