Controlling LEDs with the IRLZ44N

[Oitzu]

Hello,
a question to the hardware guys:
I try to switch some LEDs with an Arduino pro mini 3.3V.
The LEDs are connected to 12V with a 100Ohm resistor in front.
The low side of the LEDs are connected to Drain of the irlz44n.
Source to GND and Gate to 3.3V.

My problem: The mosfet doesn't seem to switch fully trough.
If i connect the low side of the LEDs directly to GND they consume 20mA.
If i connect it as described above the consume drops to 5mA and the leds are much darker.
If i connect the Gate to the 12V the LEDs are bright again.

It seems that i read the datasheet wrong at some point? Can someone point out what i read wrong?
http://www.irf.com/product-info/datasheets/data/irlz44n.pdf

[Oitzu]

I solved the problem by using a 2N700 i had laying arround.
But would be nice to know at which point i misread the datasheet.

[rvendrame]

I had a similar problem in the past, and realized that I was using IRFZ instead IRLZ, which has a higher gate threshold voltage. I replaced my 3.3V arduino pro mini by a 5V version, and that did the trick in my case.

[Oitzu]

I have both the irfz44n and the irlz44n laying around. So this is not the case.

[TimO]

I'm using an IRLZ to switch some LEDs with 9 V. The Arduino is running with 5 V.
Here is an extract of my schematics:

Source is connected to GND.
Gate is connected to PIN D5 on Arduino
Drain is connected to LED (GND).

So: +9V --> LED Device --> Drain on IRLZ --> GND.

Works for me. :-)

[Oitzu]

@TimO said:

I'm using an IRLZ to switch some LEDs with 9 V. The Arduino is running with 5 V.
Works for me. :-)

Well yeah, the IRLZ works clearly saturated with the 5V gate voltage.
But shouldn't it also saturated with a gate voltage of 3.3V? The datasheet states a Vgs(th) of 1.0V - 2.0V.
And Fig 1. specifies ID (Drain to Source Current) of nearly 19A @ 3.3V VGS (Gate to Source Voltage) / 10V VDS (Drain to Source Voltage).

Sooo... at which point i'm reading the datasheet wrong? :/

[AWI]

@Oitzu I have the IRLZ44n saturated at a little more than 2V, so maybe a misprint on a IRFZ44 package... ?

[Samuel235]

@Oitzu - Sorry to dig up an old threat, however i'm about to create a dimmer module with the mosfet in question here, an IRLZ44N, planning on switching using 3.3V. I will be creating a thread for the module as per usual with all of my creations, and i will be sure to inform this thread with my findings. If you do not hear anything from me, please remind me.

[mfalkvidd]

@Samuel235 thanks for digging it up. I had the same problem in https://forum.mysensors.org/topic/4350/irlz44n-not-fully-open-using-3-3v-arduino/ but didn't see this thread.

I ended up using a logic level converter in my kitchen light and a 5V Arduino for my wife's mirror. The leds would not shine bright when using 3.3V on the IRLZ44N.

[Samuel235]

@mfalkvidd - May i ask where you purchased the MOSFET in question from, ebay or aliexpress by any chance?

Following the datasheet the MOSFET should allow way over 2A when the gate is at 3.3V. However there is talks about it working properly/opening fully when a chinese copy/fake MOSFET is used.

[mfalkvidd]

@Samuel235 I bought this
I should probably have used the seller recommended by the MySensor store :)

[Samuel235]

@mfalkvidd - I very rarely do use the store to be honest, so we will see what my mosfets are like. If i have an order to a proper/genuine supplier i will get some ordered from there too and compare.

[Oitzu]

I wonder if i ever solved this. :D
I remember i began drawing a schematic in KiCAD. Maybe i should look if i will find this and which mosfet i used in the schematic.

[Samuel235]

@Oitzu - From the information in the past replies and your original post i thought you was using the IRLZ44N....

If you did get this working, attempt to find the part you used please.

I will order some genuine version from Farnell(Element 14) and compare the success to that of the Aliexpress version.