I've seen quite a few references to problems using non-logic level MOSFETs like the IRF510 with the Arduino.
I think I get it, but am trying to understand how the specs illustrate that.
I think the Vgs (th) is the threshold voltage, i.e. the voltage required to open the channel.
Vgs (th) for the IRF510 is 2-4V... naively, reading this, one might think it could/should be used with the 3.3V output of Arduino.
Elders on the forum have said that this IRF510 really needs 10V, and that it's Rds (on), which is 0.6 ohms is too high, so not a lot of current can be pushed.
So, why wouldn't this be marked with a Vgs (th) of 10V or some such? Seems misleading to say the threshold voltage is 3V when at that level no reasonable current will flow. Even with the 5V output of Arduino, the current through the channel is marginal.
I guess the telltale sign is to look for the "L" or some other obvious indication of a logic level device, but the smart advice seems to be to take a close look at the curves for individual mosfets before selecting one. Of course, that's the right thing to do, but when you're browsing the store that information isn't available. Especially Radio Shack
If you look carefully at the datasheet, you'll notice that the VGS rating of 2.0-4.0v is only for 250uA of current--you'll need to go to the page with the VGS vs. I graph to figure out the required voltage for a few amps of current, which is generally what you're trying to switch (it's around 10V, to save you the trouble).
And manufacturers like to rate parts in attractive ways, which is why you see 2A motor drivers which can only push 1A, transistors rated to 90V, etc.
Anyways, even if this were a MOSFET that would allow 5A with a VGS of 2.0-4.0v, I wouldn't switch it with 3.3v: that would be a partially-on state, which increases the internal resistance, leading to lots of heat. 5.0v would probably work, though.
The key is the word "threshold", This is the gate/source voltage where the device channel just starts conduction, not it's 'full-on' gate/source voltage requirements.
We tend to think only in on/off switching applications for mosfets, but mosfets can also be operated in linear modes where the threshold value would specify one end point of biasing requirements.
Yes, that's about it. Also, the fact that they give the Rds(on) at 9A for 4.5v gate voltage vs, 11A for 10v gate voltage suggests that you shouldn't try to switch more than 9A if you are driving the device from a 5v logic level signal.
Cool... yeah I am thinking of using that with an LED display project soon, it'll potentially have up to 6A going through it under pessimistic conditions (all LEDs lit at once, highly unlikely unless I make a "plastic-smelling space heater" feature LOL) so that should do it.
