# multiple 100w power Leds

Hi guys!

I am totally a beginner.
I need several advices to do my new project.

Actually it is quite simple project.
I am trying to turn on and off three or four 100w power Leds at the same time, using arduino.
It is for a performance. (I am a composer.)

As far as I learned until now,
For each 100w Led,
It runs with 32-36v (meaning current is ca. 3A).
Need driver (240v to 36v) or step up module (12v to 36v).
Need heatsink, fan and lens.
etc.

The problem is the budget is quite limited. (I need other stuff for the project)
So, to reduce the cost, what I thought is I may be able to supply 240v ac power directly to 3 or 4 Leds in series with resistor. (because I don't need to control them separately)
For example, using four Leds: (240-(32*4))/3= ca. 37 ohm
And turn it on/off with a relay module (mechanical).

It sounds simple now.
But, is this right calculation and possible in reality?

During the performance, the Leds would be only once turned on for ca. 1 minute and immediately off.
That is all.

I am looking forward to some easy advice.

So, to reduce the cost, what I thought is I may be able to supply 240v ac power directly to 3 or 4 Leds in series with resistor.

This will increase your costs because you have to replace all your equipment after it melts.

I think you're talking about COB (chip-on-board) LEDs in a 10*10 matrix with aluminium base.
The LED to base isolation is not good enough to withstand high voltage.
240volt AC rectified is almost 340volt DC.
Dangerous...
Leo..

As you probably know, high-power LEDs are normally run from special constant-current power supplies, and it generally cheaper to buy one than to build one.

The problem is the budget is quite limited. (I need other stuff for the project)

Then, how about using regular incandescent light bulbs?

240volt AC rectified is almost 240volt DC.

240VAC full-wave rectified is 240V RMS, but that doesn't help much with (non-linear) LEDs. 240VAC rectified and filtered (with a capacitor) is 336VDC.

For example, using four Leds: (240-(32*4))/3= ca. 37 ohm

If you go that route, calculate the power dissipation in the resistor (Power = Voltage across the resistor x Current through it) and make sure your power-resistor can handle the wattage.

240volt AC rectified …

Sorry, typo corrected.
Leo…