# How to circuit IRL540N logic level MOSFET

I just want to test switching my 12V 3A pump and 12V 1A solenoid valve via IRL540, and was not sure about the circuit. Below is the circuit I am planning modification to.

I read here on the forum that to limit current drwn at the gate from the Arduino a 1K resistance should be added between the arduino pin and gate. I guess that isn't the resistance shown in the pic above, so I'll have to add it? Just before the gate?

The advisor in the forum link above also says that a 10K resistance be added between the gate and the source, I guess this is the resistance picturized in the picture above? But if I do that, wouldn't the net resistance between gate and source become 11k with the other 1k added? Perhaps I should add the 1k before the link point?

Some more questions:

1. I am doing all this MOSFET testing exercise because I am currently using a relay module which I am reasonably satisfied with but don't know what's its life. It needs to switch about 1000 times a day and daily, can it take it?

2. What is the life of this MOSFET. What damages can I expect to the arduino system by ground bounce?

• Why have you deleted most of the content of your question? Commented Dec 21, 2022 at 5:45
• @PStechPaul Less garbage and more information. Commented Dec 21, 2022 at 6:21

so I'll have to add it?

You don't have to, but you'd better add it (the one below marked with green).

But if I do that, wouldn't the net resistance between gate and source become 11k with the other 1k added?

No. The 10k should be "across" the gate and source as shown in your wiring diagram. It prevents a floating gate which can cause false turn-ons. The mentioned 1k resistor should be placed between the Arduino pin and the gate. As shown below:

simulate this circuit – Schematic created using CircuitLab

And for your other two questions:

1. The datasheet of the relay mentions the minimum life expectancy: Ten million mechanical operations or a hundred thousand electrical operations. Note that these numbers are approximations so it's hard to say, for example, "Oh, after at least 100 days the relay will die". I've never seen a relay that completed its mechanical or electrical life. A bigger problem with the relays is the risk of having contact welding, and another one is they are freaking noisy. Contact welding happens if high peak currents are involved. If your motor draws really high currents when first energised (e.g. a loaded motor) then you can expect contact welding.

2. There's no exact number. Depending on the operating conditions you can expect an MTBF (Mean time between failure) of 1 to 1 million hours. It totally depends on the operating conditions. For example, the drain-source breakdown voltage of MOSFETs drops in cold environments. Likewise, the on-resistance increases in hot environments. Humidity, heatsink etc all affect the lifetime.

For ground bounce, it happens if the Arduino ground and the MOSFET ground (source, in your case) are at different levels. You can minimise the risk by keeping the wires (especially the black one shown in your diagram) as short as possible and avoiding loops.