Arduino pins can directly turn ON very low power components like small LEDs. MOSFETs are great if you need to switch ON and OFF more powerful devices that also may use higher input voltage than Arduino's 5V.
So, which type of MOSFET should you use? If you need to turn ON a device that consumes more power than an Arduino pin can provide, then you should use a Logic Level Enhancement-Type N-Channel MOSFET. It's easy to wire it up to be OFF by default and switched ON when Arduino pin goes HIGH. I have used 30N06L MOSFET to switch ON 12V motors and lamps.
Origami mario game. In this article, I will talk about different types of MOSFETs, and give the reasons why I think you most likely want to use an N-Channel MOSFET:
Logic leve N-Channel and P-Channel MOSFETs
A P-Channel JFET is a JFET whose channel is composed primarily of holes as the charge carrier. This means that when the transistor is turned on, it is primarily the movement of holes which constitutes the current flow. This is in contrast to N-Channel JFETs, whose channel is composed primarily of electrons, which constitute the current flow. It is impossible to produce the P-channel Power MOSFET which has the same electrical characteristics as an N-channel Power MOSFET. As the mobility of carriers in N-channel Power MOSFET is about 2.5 - 3 times higher, for the same Rds(on) value, the P-channel Power MOSFET size must be about 2.5-3 times of N-channel Power MOSFET. Because of larger area, P-channel device will have lower.
Disclosure: Bear in mind that some of the links in this post are affiliate links and if you go through them to make a purchase I will earn a commission. Keep in mind that I link these companies and their products because of their quality and not because of the commission I receive from your purchases. The decision is yours, and whether or not you decide to buy something is completely up to you.
What Kinds of MOSFETs There Are?
MOSFET can be either Enhancement-Type or Depletion-Type and N-Channel or P-Channel. Roughly speaking, we have four different kinds:
- Enhancement-Type N-Channel
- Enhancement-Type P-Channel
- Depletion-Type N-Channel
- Depletion-Type P-Channel
All MOSFETs have Gate (G), Source (S), and Drain (D) pins. The voltage between Gate and Source (Vgs) determines if the current is flowing through Source and Drain or not. Each kind has its own logic of when the MOSFET is turned ON or OFF. I will explain it in detail in the next two chapters.
Symbols for MOSFETs:
Python is a beautiful language to code in. It has a great package ecosystem, there's much less noise than you'll find in other languages, and it is super easy to use. Python is used for a number of things, from data analysis to server programming. And one exciting use-case of Python is Web Scraping. Use an HTML Parser for Web Scraping in Python Although regular expressions are great for pattern matching in general, sometimes it’s easier to use an HTML parser that’s explicitly designed for parsing out HTML pages. There are many Python tools written for this purpose, but the Beautiful Soup library is a good one to start with. Web scraping html table using python. Web Scraping¶ Web sites are written using HTML, which means that each web page is a structured document. Sometimes it would be great to obtain some data from them and preserve the structure while we’re at it. Web sites don’t always provide their data in comfortable formats such as CSV or JSON.
A MOSFET is classified as Logic Level MOSFET if it gets fully turned on with Vgs in the range of 3 to 5 volts. If you use a 5V Arduino board, then all Logic Level MOSFETs should be OK. If you are using a 3.3V board, then you have to check that the MOSFET you are using is compatible with 3.3V switching.
Normal MOSFETs typically need Vgs to be 10V or more to be fully ON.
Enhancement-Type MOSFET vs Depletion-Type MOSFET?
Every MOSFET is either Enhancement-Type or Depletion-Type.
Of the two types, the more common Enhancement-Type is not conducting electricity, when Vgs (voltage between Gate and Source) is zero - 'Normally OFF.' Depletion-Type is logical inversions of that, and is conducting when Vgs is zero - 'Normally ON.'
For example, an Enhancement-Type N-Channel MOSFET with a pull-down resistor will be OFF while your Arduino pin is not initialized as output (the first few seconds on startup). But a Depletion-Type will be ON in the same conditions.
![Import google contacts to icloud Import google contacts to icloud](/uploads/1/3/7/5/137563401/417040684.png)
P Fet Transistor
When deciding between those two types, you have to think of what do you want to happen while your controller board is not actively driving the MOSFET Gate. If you don't know, then pick the Enhancement-Type. It's easy to put a 10k resistor between the Gate and the Source, which makes it OFF by default.
In the rest of the article, all the examples are about Enhancement-Type MOSFETs. Everything also applies to the Depletion-Type, just the ON/OFF status would be inverted.
N-Channel MOSFET vs P-Channel MOSFET
The main difference between an N-Channel and a P-Channel MOSFET is that N-Channel usually goes to the Ground (-) side of the load (the device you are powering), and P-Channel to the VCC (+) side.
But why do you have to connect one to the negative and the other to the positive side?
Enhancement-Type ('Normally OFF') N-Channel MOSFET starts to conduct if Gate value is sufficiently higher than Source. For Logic Level MOSFETs, it's typically 3 to 5 volts. If you connect the Source to the Ground, then you can use a voltage between Ground (-) and VCC (+) to activate it.
If you decided to connect it to the VCC side of the load, then the value of the Source would also be very close to VCC. It means that you need to apply a higher voltage than VCC to the Gate to active the MOSFET. Typically you don't have this higher voltage readily available, and it makes more sense to connect the Source of an N-Channel MOSFET to Ground.
Enhancement-Type ('Normally OFF') P-Channel MOSFET is like an upside-down N-Channel MOSFET. It starts to conduct if Gate value is sufficiently lower than Source. If you connect the Source of a P-Channel MOSFET to VCC, then you can use a voltage between VCC (+) and Ground (-) to turn it ON and OFF.
Connecting it to the negative side of the load has a similar problem that the N-Channel MOSFET had. Only this time, Source would be too close to Ground. You would need to apply a negative voltage (compared to Ground) to the Gate to activate it.
It is easy to remember: you should connect the Source pin of an N-Channel MOSFET to the negative output of your power supply, and the Source pin of a P-Channel MOSFET to the positive output of your power supply.
The same rules apply to Depletion-Type N-Channel and P-Channel MOSFETs. Only ON and OFF state is inverted.
Why Prefer an N-Channel MOSFET to a P-Channel MOSFET?
Functionally you could design your circuit in a way that you could use either of them. If you have an Arduino that runs on 5V and the device you are turning ON also runs on 5V, then it doesn't even matter. You could use an N-Channel or P-Channel MOSFET as long as you wire it accordingly.
Then why prefer N-Channel over P-Channel?
- You can have a Common Ground between the 12V power source and your Arduino. With a P-Channel MOSFET, you have to create a Common VCC instead of a Common Ground. But it's standard practice to have a Common Ground between connected devices and modules. You can easily have that with an N-Channel MOSFET.
- You can power your Arduino from the same 12V power source by connecting the Arduino's barrel jack or the Vin pin to the power supply. The negative input of the barrel connector leads directly to Arduino Ground. When you are using an N-Channel MOSFET as a power switch, then that is not a problem. The Grounds are connected anyways. With a P-Channel MOSFET, we can't connect the negative output of the power supply to the Arduino Ground since the 5V pin has to be pulled up to the positive output of the power supply. By also connecting the Grounds, you will send 12 volts through the Arduino.
- N-Channel MOSFETs are more efficient than P-Channel MOSFETs. It comes down to physics. N-Channel MOSFETs use electron flow as the charge carrier. P-Channel MOSFETs use hole flow as the charge carrier, which has less mobility than electron flow. And therefore, they have higher resistance and are less efficient. In other words, a P-Channel MOSFET will get hotter than an N-Channel MOSFET with higher loads.
There are use-cases where P-Channel MOSFET is preferred or even required. For example the Arduino self-power-off circuit needs both: https://circuitjournal.com/arduino-auto-power-off
Connecting a P-Channel MOSFET to an Arduino can be a little trickier than an N-Channel MOSFET, but if you understand how it works, then it's not very complicated.
The main thing to understand about P-Channel MOSFETs is that they activate when the voltage on the Gate terminal is lower than the Source. It means that the Source of the MOSFET must be connected to the 5V output of the Arduino. Then the Arduino output pin LOW can be lower than the Source.
Symbols for P-Channel MOSFETs:
To simplify things, I am giving all the examples for the more common Enhancement-Type ('Normally OFF') MOSFETs - these are not conducting electricity when the voltage between the Gate and the Source (Vgs) is zero. The alternative Depletion-Type ('Normally ON') MOSFETs are a logical inversion of that. You can apply all the same examples and rules for a Depletion-Type MOSFET. Just the ON/OFF status is reversed.
In this article, I am going to explain all the necessary connections (and related dangers) to create the following diagram. And how to then control the power of the motor with an Arduino output pin.
Required Components
Disclosure: Bear in mind that some of the links in this post are affiliate links and if you go through them to make a purchase I will earn a commission. Keep in mind that I link these companies and their products because of their quality and not because of the commission I receive from your purchases. The decision is yours, and whether or not you decide to buy something is completely up to you.
![P-fet P-fet](/uploads/1/3/7/5/137563401/632255828.jpg)
Video Tutorial
![P type fet P type fet](/uploads/1/3/7/5/137563401/875262355.jpeg)
A step-by-step guide about using a P-Channel MOSFET with an Arduino to switch a 12V motor ON and OFF.
P-Channel MOSFET on the 12V (VCC) Side of the Load
Let's say you want to turn ON and OFF a 12V DC motor using an Arduino and a P-Channel MOSFET.
The most intuitive way to archive this goal is to wire the MOSFET on the VCC side of the load (the motor in this case).
P-fet Polarity Protection
You need to have two power sources - one for the Arduino, and a separate 12V power source for the motor.
You cannot connect the Arduino's barrel jack to the 12V! This will create a common ground between your Arduino and the 12V power supply. And it would fry the Arduino when you are creating the common VCC needed for this circuit. (With an N-Channel MOSFET you don't have this problem since you want to have a common ground between the power source and the Arduino)
You cannot connect the Arduino's barrel jack to the 12V! This will create a common ground between your Arduino and the 12V power supply. And it would fry the Arduino when you are creating the common VCC needed for this circuit. (With an N-Channel MOSFET you don't have this problem since you want to have a common ground between the power source and the Arduino)
1. First, you need to create a Common VCC by connecting the positive output of the 12V power source to the Arduino 5V pin. DO NOT CONNECT THE GROUNDS!
2. Then connect the Source pin of the MOSFET to the VCC and the Drain pin to the positive lead of the motor.
Usually, you have common Ground between devices. But in this case, we need the Arduino to be able to put -5V on the Gate terminal of the P-Channel MOSFET. Connecting the Arduino 5V pin to the VCC (and the Source) will achieve this since now the Arduino output HIGH will be 0V on the Gate, and output low will be -5V on the Gate.
3. Connect the negative lead of the motor to the negative output of the 12V power supply.
4. With inductive loads (devices that have coils in them) like a motor, you need to add a flyback diode. It's a diode that is connected across the load in a reverse direction of the normal current flow. During motor operation, it doesn't do anything. But when the MOSFET switches OFF, the coil inside the motor will continue pushing electrons forward and will create a voltage spike. This can damage your MOSFET. The flyback diode allows the excess induced current to flow back and circulate inside the motor until all the energy is dissipated.
5. Add a 10k resistor between the Gate terminal and the VCC. It will ensure that the MOSFET is OFF while the Arduino pin is not initialized as OUTPUT yet, and is not actively driving the Gate (during startup, for example).
6. Finally, connect the Arduino digital output pin to the Gate via a 100-ohm resistor.
The 100-ohm resistor is necessary since the MOSFET will have a small internal capacitance. When you switch the digital output pin, it will start to charge/discharge, and it will create a current spike that can damage the Arduino Arduino pin, especially if you plan to do high-frequency switching.
P-Channel MOSFET on the Ground Side of the Load
I'll give this alternative connection diagram for educational purposes. Maybe it helps to understand the P-Channel MOSFET better.
You can also connect a P-Channel MOSFET below the load on the negative side of the power source. But here we don't have a common Ground nor a common VCC with the 12V power supply. Arduino 5V and GND pins are floating somewhere between the + and - outputs of the 12V power supply because there are no direct connections to them.
Since the MOSFET is activated or deactivated based on the voltage between the Gate and the Source, we need to make sure that the Arduino 5V pin is on the same level as the Source. So we need to connect the Source directly to the Arduino 5V pin.
It's the same case here that you cannot connect the grounds of the power supply and the Arduino! If you do that, you will apply more than five volts to the 5V pin (through the motor).
Dc Volts On Off Switch Using P-fet
Arduino Code to Control the MOSFET
To drive a P-Channel MOSFET, you have to define one of the Arduino pins as OUTPUT and set it to HIGH to turn it OFF and set it to LOW to turn it ON.
HIGH state is OFF because the Source pin of the MOSFET is connected to the 5V output of the Arduino. It means that Vgs (voltage between the Gate and the Source) is 0V, and an Enhancement-Type MOSFET is turned OFF in this circumstance.
P Fet Symbol
The following code will turn a motor ON and OFF every five seconds:
P-fet Short 412
If you are controlling a motor or a lamp that can handle a PWM signal, then you can also use analog write command. For example, this will drive a motor at half the power or dim a LED light to 50 percent: