Here I'm trying to build a PWM high side driver using IRF9540N with the control of Arduino.I used a power 12V 3W LED (~280mA) as the load.When I directly connected the LED to a battery, my current consumption was 280mA and while I try the high side circuit, it's consumption is ~190mA. I tried changing the resistor values of R1, R2 & R3.
My problem is that on PWM action or ON/OFF action my current consumption is being scaled to 0 to 190mA,whereas it should be scaled from 0 to 280mA.

I have tried different circuits it's the same result.

Please help me find the solution. It's an urgent project.

 

hi,
You are using a P MOSFET, check the voltage polarity for the Drain of the device as wired in the circuit, also that MOS has an inbuilt diode which is forward biased in that configuration,.
E

 

This just means your PWM signal is running at 64.28 % of it's duty cycle.

Turn up your duty cycle to get more mA.
Here's how.

If you had proper equitment you would see that it actually goes up to 280mA, but it happens so quickly you can't measure it without an ocilloscope.

 

hi PRASS,
The MOS is a P type , it is wired upside down.
E
Corrected the circuit, improved sim.

 

this was my actual circuit.

This just means your PWM signal is running at 64.28 % of it's duty cycle.

Turn up your duty cycle to get more mA.
View attachment 229061Here's how.

If you had proper equitment you would see that it actually goes up to 280mA, but it happens so quickly you can't measure it without an ocilloscope.

do you mean by changing the resistor values?

 

this was my actual circuit.

do you mean by changing the resistor values?

Or what should I do?

 

hi shar,
Your MOS FET was upside down, didn't you read my posts. post #4.
It works fine as the post shows.
E
Remove that 1uF capacitor

 

this was my actual circuit.

do you mean by changing the resistor values?

Somewhere in your Arduino code you will find a piece saying analogWrite() is on a scale of 0 - 255, such that analogWrite(255) requests a 100% duty cycle (always on), and analogWrite(127) is a 50% duty cycle (on half the time) for example.

If you would like just put your code here as a comment & I will find it for you

 

Or what should I do?

I use this same mosfet for high side switching. You have the drain and source connected wrong.
Drain should connect to load, source should connect to +12.

see post #4

 

Somewhere in your Arduino code you will find a piece saying analogWrite() is on a scale of 0 - 255, such that analogWrite(255) requests a 100% duty cycle (always on), and analogWrite(127) is a 50% duty cycle (on half the time) for example.

If you would like just put your code here as a comment & I will find it for you

int z = 0;
void setup() {
pinMode(3, OUTPUT);
pinMode(A5, INPUT);
Serial.begin(9600);
}

void loop() {
int v = analogRead(A5);
float volt = v * (5.0 / 1024);
float batt = (volt * 12200) / 2200;
analogWrite(3, z);
if (z < 241)
{ z = z + 10;
delay(2300);
} else if (z > 240 && z < 256)
{
z++;
delay(1200);
}
else if (z > 255)
{
z = 0;
}
Serial.println(v);
Serial.print("Batt:- ");
Serial.println(batt);
}

 

hi shar,
Your MOS FET was upside down, didn't you read my posts. post #4.
It works fine as the post shows.
E
Remove that 1uF capacitor

I kept that capacitor so that it reahces around 200mA or else its around 170mA

 

If the PWM is 100% (DC) or a very low frequency then the capacitor would not use a lot of charging and discharging current.

 

I kept that capacitor so that it reahces around 200mA or else its around 170mA

If the MOSFET is wired correctly, you’ll get the full 280mA and you won’t need the capacitor. So remove it when rewiring the MOSFET.

 

If the MOSFET is wired correctly, you’ll get the full 280mA and you won’t need the capacitor. So remove it when rewiring the MOSFET.

Bro i wired it correctly but what i uploaded to this forum was wrong(pins of mosfet)

 

Bro i wired it correctly but what i uploaded to this forum was wrong(pins of mosfet)

I’m not your bro

 

If the PWM is 100% (DC) or a very low frequency then the capacitor would not use a lot of charging and discharging current.

Tell me how to solve the issue ,does changing resistor values work?

 

hi,
As a test short out the 2N2222, ie: across Collector to 0V, now measure the LED current, post what you measure.
E

 

/*
Here try out this code.
I got rid of bundles of unnecessary code for you.
I highlighted the easy way to change the PWM in red.
It is set at 100 % duty cycle now but if you change the 255 number to anything below 255 it will decrease the duty cycle also.
eg; 127 will give you 50 % duty cycle & 63 will give you 25 % etc etc.

I will also drop a 2 pictures of a much easier way to create your circuit.
Because it's ok to run an Arduino from 7 to 12 volts.
*/



void setup() {
pinMode(3, OUTPUT);
pinMode(A5, INPUT);
Serial.begin(9600);
}
void loop() {
int v = analogRead(A5);
float volt = v * (5.0 / 1024);
float batt = (volt * 12200) / 2200;

analogWrite(3, 255);

Serial.println(v);
Serial.print("Batt:- ");
Serial.println(batt);
}

 

hi PRASS,
You need a 0V line from the 12V battery to the Arduino 0v.
Also the LED is reversed.
E

 

/*
Here try out this code.
I got rid of bundles of unnecessary code for you.
I highlighted the easy way to change the PWM in red.
It is set at 100 % duty cycle now but if you change the 255 number to anything below 255 it will decrease the duty cycle also.
eg; 127 will give you 50 % duty cycle & 63 will give you 25 % etc etc.

I will also drop a 2 pictures of a much easier way to create your circuit.
Because it's ok to run an Arduino from 7 to 12 volts.
*/



void setup() {
pinMode(3, OUTPUT);
pinMode(A5, INPUT);
Serial.begin(9600);
}
void loop() {
int v = analogRead(A5);
float volt = v * (5.0 / 1024);
float batt = (volt * 12200) / 2200;

analogWrite(3, 255);

Serial.println(v);
Serial.print("Batt:- ");
Serial.println(batt);
}

View attachment 229099 View attachment 229100

The MOSFET shown in your second picture is a P channel MOSFET which usually is used to switch the high side. You have it on the low side. It also must be a logic level MOSFET as the Arduino GPIO can only provide 5V (at most). Just because you can power the Arduino with 12V doesn’t mean you can connect 12V devices to it (without driver circuitry). The 12V input goes through an onboard voltage regulator, bringing the MCU voltage down to 5V. Your diagram is missing a lot of information and likely won’t work.