Need help with selecting a MOSFET P-Channel.

Hi.
I hope you all fine out there.

I need some assistant to select a MOSFET for controlling on/off min 12 Volt at 5A load.

From Arduino/ESP or a Raspberry Pi with 3.3V GPIO.

Most important is that I really need to cut on/off on the positive.

Please check my simple drawing and please guide me, I can’t figure this out.

I would love a part number

MOSFET-P.JPG

I would use an N channel logic MOSFET switching on the low side of the load. What calls for switching on the high side? I see no reason in You drawing.

MOSFET PDF

You have the drain and source backwards. The 12V power should be connected to the source, and the load connected to the drain. Mosfets will conduct equally well in either direction, but they have a body diode that must block the switched current unless the mosfet is on. See the datasheet diagram for the NDP6020P, which would probably be a good mosfet to look at.

Also, I know nothing about the Pi, but if the GPIO ports are 3.3V, then your pullup resistor on the gate should be to 3.3V, not 5V.

Edit: No, I was completely wrong about the gate. The gate would have to be at 12V to turn off the mosfet, and you can't connect 12V to a 3.3V GPIO pin, even through a resistor. Current would flow through the protection diode on the GPIO pin to the 3.3V rail, and the mosfet would never turn off. So Railroader is right - you need to use an N-channel mosfet and switch the low side.

Railroader:
I would use an N channel logic MOSFET switching on the low side of the load. What calls for switching on the high side? I see no reason in You drawing.

When you have common ground to all things , example a boat or car, then sensors might been grounded and then get power from that ground connection.

larryd:
MOSFET PDF

https://forum.arduino.cc/index.php?action=dlattach;topic=445951.0;attach=354033

I read about 20 pdf with spec, but still unsure what to pick that fit my needs :slight_smile:

You want a low Rdson at the Vgs you are using, a reasonable Vgs max. and a current rating > than you need, a Vds max > your supply.

An AO4409 might work if you are switching at 5v.


FYI


oops, a NDP6020 is an N channel MOSFET :frowning:

fableman:
When you have common ground to all things , example a boat or car, then sensors might been grounded and then get power from that ground connection.

Fit the logic N-channel MOSFET between the low side of the load and the common ground. Does the motor have built in sensors? I doubt that.

Schematic # 3 here:
https://www.gammon.com.au/motors
Drop R1 to 680 Ohms.

Railroader:
Fit the logic N-channel MOSFET between the low side of the load and the common ground. Does the motor have built in sensors? I doubt that.

Please stop telling me to switch on the low side!
I can not do that in my build, and I never said anything about a motor.

JCA34F:
Schematic # 3 here:
https://www.gammon.com.au/motors
Drop R1 to 680 Ohms.

Still switching on low side.

larryd:
You want a low Rdson at the Vgs you are using, a reasonable Vgs max. and a current rating > than you need, a Vds max > your supply.

An AO4409 might work if you are switching at 5v.


FYI


oops, a NDP6020 is an N channel MOSFET :frowning:

Thank you very much of the examples you shared.

AO4409 MOSFET. Datasheet pdf. Equivalent
Type Designator: AO4409

Type of Transistor: MOSFET

Type of Control Channel: P -Channel

Maximum Power Dissipation (Pd): 3.1 W

Maximum Drain-Source Voltage |Vds|: 30 V

Maximum Gate-Source Voltage |Vgs|: 20 V

Maximum Gate-Threshold Voltage |Vgs(th)|: 2.7 V

Maximum Drain Current |Id|: 15 A

Maximum Junction Temperature (Tj): 150 °C

Total Gate Charge (Qg): 51.5 nC

Rise Time (tr): 16.5 nS

Drain-Source Capacitance (Cd): 945 pF

Maximum Drain-Source On-State Resistance (Rds): 0.0075 Ohm

Would even work with 3.3 Volt ! thanks a lot for the info!
Cheers!!!

This one, load does not have to be a motor.