Power MOSFET Driving Big Motor Problem

Question

I am using the power MOSFET IRF504N. I am not sure if my Rpi's GPIO 3V3 signal can directly input to the gate of the MOSFET which requires 4V minimum.

I guess that I don't need a gate driver to shift up the Rpi's 3V3 signal. So I am now experimenting, ...

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I read the IRF540N datasheet which says Vgs(th) is 2V minimum and 4V maximum. Does it mean Vgs between 2V to 4V won't guarantee anything?

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I forgot to mention that the motor is DC12V 100mA (37GB528-70 70rpm). And I also want to drive another solenoid valve DC12V 300mA (FDZ-5). The picture below shows the two little guys.

Motor and Solenoid Valve Picture

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^{simulate this circuit – Schematic created using CircuitLab}

Answer 1

This might work, but it won't work well.

The parameter you've asked about (Vgs(th) is 2V minimum and 4V maximum) means this:
The threshold voltage at which conduction begins from Drain to Source is a minimum of 2 V, and a maximum of 4 volts. Since the RPi GPIO is 3.3 V, there will be some devices that may not conduct at all. See Fig 3 in this spec sheet.

Bottom Line: You need to drive your chosen MOSFET with a much higher voltage than the 3.3 V available from the RPi GPIO pin if you want your circuit to operate "properly" (within design specifications). You should have around 7 V gate-source voltage for best results - at least for this MOSFET.

Answer 2

OP asks if Rpi 3V GPIO signal can trigger the N-channel power MOSFET IRF540N with trigger threshold >4V to drive (a) 12VDC 35mA motor, (b) 12VDC 250mA solenoid.

A short answer is that RPi's 3V GIPO high signal can likely trigger and slightly turn on the IRF540N's channel to barely pass through <50mA and therefore can slowly move a 35mA DC motor. However the barely opened channel with high Rds on resistance does not allow enough current to drive a >100mA solenoid.

There is a get around - use a 3V/5V logical level trigger alternative such as IRL540N.

References

(1) AN11158 Application Note Understanding power MOSFET data sheet parameters - Rev. 6.0 — 2020jul06