MOSFET choise...

Other Hardware General Electronics
1

Hello!
I'm looking for the right MOSFET for a project like this one (RGB LED strip on beat + some extra functions that I wrote my own with remote controll, I'll upload the code when it's done :wink: ):
schematic .
They use IRF 520 as MOSFET: datasheet.

I can see that gate to threshold is 2V-4V, so then it begins to conduct current to my led strip. Max gate voltage is 20V. So isn't it strange to use this MOSFET?

Would for example a FQP30N06L Datasheet(PDF) - Fairchild Semiconductor ( datasheet ) be better.

NOTE: I've just been searching the web for a while. I don't know anything of MOSFETS, so there are probably some errors in this message :roll_eyes:

MODIFICATION: Led strip takes 12V - 2A

Thanks!
Bram

2

Yes, they did it wrong.

IRF520 is not a logic-level MOSFET. You need one with "logic level" in the name, eg. IRL540.

(The 'L' in 'IRL' is for "Logic Level")

3

PS: Yes, the FQP30N06L will work.

4

See Image also:
Vgs(th) is 2.5V (page 2)

2014-04-01_13-23-00.jpg
2014-04-01_13-23-00.jpg386×520 59.1 KB

5

Thanks fungus for the correction and LarryD for the scematic!

So I understand that any logic level MOSFET should work.
But I read then you still have options that are better than other ones (it had something to do with the resistance R). Does anyone have an idea what I should look for on a datasheet to pick the best fitted one?

P.S.: LarryD, if you read this: what program do you use for making your schematics?

6

Look for:
Logic-Level Gate Drive
Low value for RDS(on) (?), IMO I like less than .1 Ohms(100 milli ohms) (lowest possible)
Drain-Source Voltage, to be greater than your power supply
Continuous Drain Current, to be greater than your load will require

I use WinQcad no longer available.
Try Fritzing, Eagle, Kicad OR search the forums as it has been discussed here many times.

http://www.cadsoftusa.com/
http://www.kicad-pcb.org/display/KICAD/KiCad+EDA+Software+Suite