LED strip with mosfet

Hi, there.

I've got an arduino controlling several LED strips (12V) via IRLZ44N mosfet. Each strip contains 6 LEDs (0.72W x 6 = 4.32W). It seems IRLZ44N cannot maintain such current in longer period of time, because, eventually they burned out :slight_smile:

Maybe you, guys, know is there some other mosfet that could deal with such current? Or some bigger heat sink should do the trick?

Thanks.

Yes, IRLZ44 do have sort of "high" r_ds(on).
A heat-sink more substantial than some clip-on job is likely in order.

Each strip contains 6 LEDs (0.72W x 6 = 4.32W).

No, that can't be correct. That's 10 x too high.

6 leds should be about 0.48W or 360mA. That's not going to be any problem at all for a power mosfet. Even 10x as much current should not even get it warm. Something else is wrong.

It is indeed around 4-5W. I'm using something (ain't exact model) like this:

with it's own 12V power supply, which also powers Arduino via buck converter.

5W at 12V is 417mA. That mosfet is rated for 47A.

6 leds should be about 0.48W or 360mA.

Sorry, typo. I meant to say 40mA.

How about showing a circuit diagram ? What is the measured current the LEDs are taking ?

And what are you actually doing with the MOSFET ? If it's just switching the LEDs it should be no problem. The only way people usually have any trouble is running the MOSFET permanently in linear mode and even then at less than 0.5A it should be o.k.

Steve

I found a data sheet for these leds here. Each module (containing 3 leds) is 0.5W, 45mA.

So when the OP says “6 leds per strip” they actually meant 6 modules, that would be 3W and 270mA. If when the OP said “several” they meant 20, all controlled by a single MOSFET, that would be 5.4A, still less than 10% of the max for the MOSFET.

So there is no problem with the model of MOSFET. Something else is wrong here. Perhaps the MOSFET(s) are from a rejected batch that were sold on cheaply on eBay. Or as Steve suggested, they are not being used in their fully on state for some reason.

I meant 6 LED modules ( eventually there are 3x6 = 18 ). Basically there are 11 strips and sequentially one is turned off for 0.1 sec. So 10/11 of time gate is open. Arduino gives out ~40mA, 5V, so it should be fully open.

Depends how you have it all connected e.g. what is in series and what is parallel. What is the power supply ? We still haven't seen anything like a circuit diagram.

As far as I can guess at what you seem to be describing it should work with no problem.

Steve

Circuit diagram is like this

but with 11 strips instead. I did marked each LED module as single LED, cause don't know if they are as serie or parallel inside (modules must be series). On module it's written 0.72W though.

Also case must have a little to do with burning, because MOSFETs where places vertically, like this:

so the top ones were first to go..