Gate and pull-down resistor values for MOSFET and Arduino Nano

Other Hardware General Electronics
41

First of all, thanks for helping me out!

stuart0:
BTW. Have you re-tested the led strip (without the mosfet) to make sure that it's not damaged?

Yup, strip is good and also works pretty well with other FET: IRF540.

TomGeorge:
Did you measure the voltage at the gate and the drain when you were switching the MOSFET ON and OFF?
Make sure you have the 10K from gate to source connected ALL the time.

I haven't measured the actual voltage on the gate, just on arduino pin. As for the drain – yes, I've measured it on the LED strip. OFF is 0V and on was 8.1V, for IRF540 it is 9.7V. It's not 12V because of quite lousy jump wires, but even with those the performance of IRF540 is significantly different from IRL2505.

TomGeorge:
Also measure your 12V supply when you switch ON and OFF?
What is your 12V supply?
A picture of your project will help, so we can see your layout.

It's a 12V 4.16A PSU from a computer display (looks like the one used for laptops). Haven't measured the actual voltage there, but I don't think that's an issue, because when I connect 12V from that PSU to the FET's gate, it switches fully ON. Pictures coming in the evening (EET), since I'm at the office now :slight_smile:

42

So I've ended up making a different setup to completely eliminate lousy jump wires and breadboard. And this time the IRL2505 performed flawlessly and IRF540 almost the same. First I've tired with PSU from desktop PC, so I've used it's 12V and 5V wires. With 5V connected to FET, voltage on the strip was exactly the same, as when it's connected directly to PSU: 11,3V (I measured it not on the tip of the strip, but in the middle, that's why not 12V).
IRF540 did slightly worse: 11,0V.

After that I've soldered everything onto a PCB together with Arduino Nano and it worked.

So the main issue was in jump wires and breadboard. Although one question that is still open (and that initially got me into this confusion) is why IRF540 was performing way better on the breadboard than IRL2505, given that they were plugged in same sockets?