I have 12 leds in parallel how do i connect them to a transformer and what do i need?

Question

I have 12 leds in parallel how do i connect them to a transformer and what do i need?

Answer 1

You'll need to make a DC voltage from your transformer first - you can do this with a full-wave (bridge) rectifier. I'd also recommend some filtering and a basic linear voltage regulator to cut down the ripple.

Beyond this, you'll wire your LEDs in series, parallel, or series/parallel to make the best use of your voltage.

The simplest setup would be to use several sets (3 or 4) wired in series with one dropping resistor per string. This would be good for a 12V supply.

That said, there's not a problem wiring them in parallel as long as they're *exactly* the same (same type, same vendor.) If they're not, then you should add small dropping resistors to each one to cover the mismatch to ensure equal brightness.

Link below gives more details.

Answer 2

LEDs will not work properly when connected in parallel. They have different voltage drops (VF), and the one with the lowest VF will take all the power, and the others will get less, some will get none, some will get too much and burn out.

Each LED needs a series resistor that will drop about 2 volts. Size depends on the current spec of the LED, but 100-200 ohms is typical.

LEDs work best on DC, so you don't want to connect them to a transformer, you need a power supply.

You can put LEDs in series strings with only one resistor per string, and that can be a better connection method for many cases.

You can get a 12 volts DC supply good for about 100 mA.

Then string the LEDs in series in groups of 4, with a 400 ohm resistor (about) in series with each string.

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Answer 3

Any particular reason you're connecting LEDs to a transformer?

Transformers require an AC power source, LEDs work on DC power.

I Suppose you could use the LEDs to rectify your AC input, but they're really not built for that ;)

Peter

How Your Electronics Work

http://www.howyourelectronicswork.com