Hello,
I'm trying to switch a Mosfet IRFZ24 with an Arduino but it doesn't seem to work.
I'm assuming I'm not reaching the minimum voltage at the gate but I can't find what it is
In the datasheet, only the max voltage is specified (+/-20V) - unless I missed something
https://docs-emea.rs-online.com/webdocs/009f/0900766b8009fbd2.pdf
Does anyone have any experience with one of those ?
Thanks
At 10v Vgs, the RDS(on) is .07Ω
Use circuit Q4 and Q5 with your transistor.
Show us a good schematic & image of your circuit.
Posting images:
http://forum.arduino.cc/index.php?topic=519037.0
What are you trying to switch with it? Particularly, how much current? This isn't what you'd call a logic level MOSFET but if it's a small enough load you're trying to drive and it's the only one you have for now, it can still work.
Figure 1 and 2 of the datasheet give you the details of how "on" it will be with various values of VGS
Thank you both
@saximus: I'm trying to switch a transducer (40KHz) which is rated at 35W. The schematics below worked well so far using a 2222 with a 5V supply but I need extra power for my application hence the use of the Mosfet.
I will try to put my hands on a more adequate mosfet or power transistor
@larryd, here's a schematic which looks like the Q4 bit only
It is perhaps a minor point, but when driving a FET, the 10k resistor is in the wrong place. It should not be between gate and source. Its only purpose is to define the Arduino output during initialisation, so it should be between the Arduino pin and ground. The "fault" it corrects belongs to the Arduino, not the FET.
What are you use a 35W ultrasonic transducer for?
Killing whales? ???
Your transistor is not a ‘logic level’ MOS FET.
If you insist on using this MOS FET you need to use similar to the Q5 and Q4 circuit.
No experience driving a power transducer, but class-A with a load resistor seems wrong and inefficient for a capacitive load.
At least for this power level.
Are you sure the transducer is performing at it's power level with only 7volt AC across?
Get rid of the IRF type of fet.
They don't belong in the micro processor world, unless you put a mosfet driver in between.
Leo..
Paul__B:
It is perhaps a minor point, but when driving a FET, the 10k resistor is in the wrong place. It should not be between gate and source. Its only purpose is to define the Arduino output during initialisation, so it should be between the Arduino pin and ground. The "fault" it corrects belongs to the Arduino, not the FET.
Ah that's good to know - thanks a lot!
larryd:
What are you use a 35W ultrasonic transducer for?Killing whales? ???
Your transistor is not a ‘logic level’ MOS FET.
If you insist on using this MOS FET you need to use similar to the Q5 and Q4 circuit.
Haha 
I'm actually trying to transmit power through a thick plate of steel with another transducer on the other side. Thanks a lot for confirming this is not the right mosfet, I will try another one then !
I'm actually trying to transmit power through a thick plate of steel
But using one of the most inefficient circuits for that purpose.
Push-pull drive (class B) is essential for good power levels and efficiency. Class A is always a mistake
with power electronics.
A half-H-bridge like a BTS7960 or half of the VNH5019 might be much more suitable.
MarkT:
A half-H-bridge like a BTS7960 or half of the VNH5019 might be much more suitable.
Or a full H-bridge if you need double the drive voltage.
That way the piezo is also driven by pure AC (no DC component that could result in migration issues).
Leo..
That's a point, bridge-tied configuration would give 40V peak-to-peak. Needs to be a fast enough
MOSFET H-bridge at 40kHz, though, that needs checking.
I use one of these for driving mosfets: Low Side Driver
You can control what the gate voltage is external to the microcontroller - and can definitely avoid latch-up issues.
There are other drivers that can be used to drive an N channel mosfet on the high side. This is an example in Infineon's line up - there are many: High Side N channel Driver This one can be configured in boot strap mode for pulses - will not work for a sustained 'on' condition.
Both devices are just examples of interfacing the microcontroller world with high power devices.
Thanks a lot guys. That's very useful info, I'll go back to the drawing board as it seems much more complex than I thought
Not at all unusual. 
