Led dimmer sketch, voltage drop?

[Cliff Karlsson]

I just uploaded the led dimmer sketch to an pro mini 3.3v with an IRFZ44N mosfet connected and a led strip. It works as it should but I was getting a feeling that the ledstrip was a little dimmer at full brightness, so I tested with a voltmeter. I have a 12v power suply and if I connect it directly I get ~11v. If I use mosfet I get around 8.5v. Why is that and can I do anything to fix this?

[Drcashman]

The IRFZ44N is not a logic level mosfet. A pro mini 3.3v will not fully open the gate.

I had the same issues so I went with a IRLZ44N and it works great.

[Cliff Karlsson]

Ok, how much voltage/current is needed to open the gate? I changed to a Nano and now I get ~10v

[Yveaux]

@Cliff-Karlsson said:

Ok, how much voltage/current is needed to open the gate? I changed to a Nano and now I get ~10v

First, I'm a software guy, but I'll try to answer your question. Please correct me if I'm wrong!
I started to type an answer to your question, but it has already been answered many times on the web, e.g. http://electronics.stackexchange.com/questions/144607/do-mosfets-have-voltage-drop-across-source-and-drain-when-turned-on
And for the full background http://www.microsemi.com/document-portal/doc_view/14692-mosfet-tutorial

For your IRFZ44N look up the Vgs chart in the datasheet (http://www.irf.com/product-info/datasheets/data/irfz44n.pdf, page 3, figure 3).
You can see that 4.5 Volts is roughly the bare minimum to get the Mosfet to open its gate, but the maximum current is only about 10Amps there. At 7 Volts it can switch 100Amps -- should be sufficient for your LED strip ;-)
Either use e.g. a transistor to switch it using a higher voltage, or use a logic-level mosfet, as @Drcashman suggested.