Well, in http://sigma.octopart.com/86397/dat...IRF530.pdf they call it Vgs(th)

However, that's just the point at which it begins to conduct. In order to get it to function fully, you have to raise the Vgs to about 10 volts, as indicated by most of the parameters specified in the datasheet.

This (IRF530) is not the type of transistor you want to use. There are logic MOSFETs that have a more favorable characteristic with respect to Vgs. What's more, a lot depends on the circuit configuration in which you wish to use it. You haven't stated whether it is switching the high-side or the low side of your load. N-channel MOSFETs, given sufficient Vgs, will switch the low side of your load just fine. If you want to switch the high side, i.e. from Vcc to your load, you probably want to use a p-channel MOSFET.

This (IRF530) is a power MOSFET of the sort you'd use to drive a motor or other load that requires lots of current, possibly from a higher-voltage supply, e.g. 25-80 volts. It's rated at 14 amperes and 100 volts. If you're driving a LED that requires less than 500 mA of current, you probably want a much smaller device, and that's exactly the sort that will include the logic-driven types that will suit your application much better. If you look for a prefix like IRLD, (have a look at IRLD120, for example) rather than IRF, you'll find a number of transistors that respond to voltages your MCU can provide, and which are smaller and more convenient to use. Further, the physical size of the device says something about the gate capacitance, which the MCU will have to drive, too.

If you Google on "logic MOSFET" you'll find lots of information, some of which is actually quite useful. I've tended to use really small relatively modern transistors recently, and buy the ones that come with both a p-channel and an n-channel MOSFET on the same chip. The ones I use (I don't have the part numbers on hand, as I'm in the midst of moving) are in SO8 package and have a very low on-resistance (less than 0.1 Ohm) when driven to logic levels and operating from a 5-volt supply.

I'd also suggest that you Google for "high-side MOSFET switch". That will not only give you some circuit recommendations but will show you some parts that might be better suited to your application than the IRF-series.

RE