So, my understanding of electronics is very limited, but as I understand what i'm reading, an Nchannel mosfet switches on the low side of the circuit (negative lead) and a Pchannel mosfet switches on the high side of the circuit ( positive lead). so, if I were to switch out an Nchannel fet for a Pchannel fet, I would simply be changing which side of the circuit is being switch, right?
Yes, N-channel connects to Gnd, P-channel connects to power supply.
N-channel, you can find Logic Level gates that will switch fully on with 4.5 to 5V Signal
Most P-channel need a 10V swing, so a pullup resistor to power supply is used to turn them off, and a NPN or small N-channel is used to pull their gate low to turn them on (which an arduino can drive thru a small resistor).
So you have to take into accounts how the gates are driven.
FYI
Some examples I’ve used:
https://forum.arduino.cc/index.php?action=dlattach;topic=690136.0;attach=368349
LOW/HIGH side:
Examples:
Read this.
Leo..
https://www.vishay.com/docs/91021/91021.pdf
https://www.vishay.com/docs/91086/sihf9640.pdf
so, i'm looking at these two mosfets, N and P channels, and I cant see where you're talking about needing an up swing to 10v to switch. the Vgs shows -10v for the Pchannel and 10v for the Nchannel.
I'm sorry if my questions seem overly simplistic, i'm trying to understand how this works.
for context, this is what i'm working with right now for prototyping. these are IRF540N mosfets. again, I know i'm working above my skill level, but i'm really trying to get this. are these resistors setup as pulldowns instead of pullups?
These two MOSFETs need 10v to get the stated:
“Drain-Source On-State Resistance RDS(on)”
BTW, these ‘are not’ logic level MOSFETs.
Tell us what you will be doing.
Show us a good schematic of your circuit.
Show us a good image of your ‘actual’ wiring.
Give links to components.
Posting images:
https://forum.arduino.cc/index.php?topic=519037.0
All the specifications are at Vgs=10volt, so not a logic level mosfet.
These fets shouldn't be used with 5volt logic Arduinos, and can't be used with 3.3volt logic.
Logic level fets are (also) specified for Vgs=4.5volt.
They usually have the letter 'L' in their part number.
Leo..
larryd:
These two MOSFETs need 10v to get the stated:“Drain-Source On-State Resistance RDS(on)”
BTW, these ‘are not’ logic level MOSFETs.
so, in this instance, I could replace the existing IRF540N with the IRF9640?
I'm attempting to control a 3 wire ballvalve from us solid. I know I can't do low side switching with the IRF540N, what I have controlling my 12v components is one of these
What's the chip in the middle?
The chip is a 4-way opto coupler.
The mosfet gates are most likely driven from the load supply.
The Arduino only drives the opto LEDs.
No, you can't just replace the N-channel fets for P-channel fets without completely re-designing that board.
Leo..
so, I know i'm asking for work to be done, but what would the circuit look like for a P channel mosfet?
Thank you everyone for assisting with helping me understand this process.
Everything to the right has to be flipped upside-down.
P-channel source, R3, LED, to VPP.
Opto and load to ground.
LED and opto polarity the right way of course.
Q: Why.
Leo..
I need a solution for high side switching of 12v motorized ball valves
If you don't need opto isolation, then use the third diagram in the link of post#3.
Leo..