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I'm gonna start to excuse me for my bad soldering/layout, but this is my project.

enter image description here

I am using a mosfets (IRF520) to which I have connected a 12V power source to the drain and source. They are connected up to a led strip. The gate I am controlling with my arduino MKR1000 (3.3v outputs). The circuit does exactly what I expect from it except for one thing: the leds dont burn as bright as I would expect. When I connect a 12v input to the gate they do burn as bright as I expect. My guess is that it is because the voltage I put on the gate is too low, and the mosfets are acting as a variable resistance.

The store I bought them though tells me that they should burn as bright with 3.3v as with 12v. Am I doing something wrong, or am I using the wrong mosfets?

Schematic I used:

enter image description here

Link to datasheet: https://www.vishay.com/docs/91017/91017.pdf

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    \$\begingroup\$ There is a schematic tool button on the editor toolbar. Please add a schematic so we know what you are describing. \$\endgroup\$ – Transistor Oct 29 '17 at 20:21
  • \$\begingroup\$ And link to the IRF520 datasheet. \$\endgroup\$ – Brian Drummond Oct 29 '17 at 20:23
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    \$\begingroup\$ @Terabyte: That's not a schematic - it's a wiring diagram. It shows how the bits are wired up but not the "scheme" or how it's supposed to work. A schematic shows symbols for the transistors, etc., showing their gate, drain and source. In this case you'll probably get away with it but generally those diagrams are frowned upon (gross understatement). \$\endgroup\$ – Transistor Oct 29 '17 at 20:29
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    \$\begingroup\$ The store I bought them though tell me that they should burn as bright with 3.3v as with 12v. This is sellers' talk, this is not true. All the led strips that I already saw had a resistor for each section of leds, and as the resistor is the same, the led's bright will not be the same with 3.3v or 12v. Try connecting the 12v directly to the strip, and see if the source really withstands all this strip. \$\endgroup\$ – mguima Oct 29 '17 at 20:34
  • \$\begingroup\$ @Transistor My apologies, but I am a proper beginner :) \$\endgroup\$ – Terabyte Oct 29 '17 at 20:45
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I think your Vgs is too low. You could easily check this by connecting the gate to VUSB or even the 12V as you did. I used IRF520 with 3.3V logic and had to use a higher voltage transistor coupling to the gate to increase Vgs.

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  • \$\begingroup\$ To be honest, i'd prefer to replace the mosfet with another one that will work with 3.3v. Do you by any chance have a suggestion for a replacement mosfet? \$\endgroup\$ – Terabyte Oct 29 '17 at 20:32
  • \$\begingroup\$ I guess you want through hole? \$\endgroup\$ – Dejvid_no1 Oct 29 '17 at 20:32
  • \$\begingroup\$ What do you mean by "through hole"? \$\endgroup\$ – Terabyte Oct 29 '17 at 20:37
  • \$\begingroup\$ I googled it, and my answer is yes :) \$\endgroup\$ – Terabyte Oct 29 '17 at 20:38
  • \$\begingroup\$ Like the one you have on your board. For mounting in a hole. Not surface mount. Anyhow: IRLZ44N or IRF3708 \$\endgroup\$ – Dejvid_no1 Oct 29 '17 at 20:39

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