# Powering Pump using Teensy 4.1 + MOSFET FQP30N06L + MOSFET Driver NCP81074

#### roboticsmick

Joined Oct 10, 2021
3
Hi all, I was hoping to get some advice on how to switch on a pump using a teensy 4.1 + MOSFET FQP30N06L + MOSFET Driver NCP81074. I'm not sure where I am going wrong?

When I power the 12V line with a 5V source the gate turns on and the motor runs, but when I swap the voltage source to a 7.4V or 12V battery the gate doesn't switch on? My schematic and code are below:

Any advice on my error or where to research to fix my issue would be awesome!

Thanks in advance for any help!

Cheers,

Mick

Turn on gate - Teensy 4.1:
#include <Bounce2.h>
// Teensy 4.1
#define PUMP_POWER_PIN 23
#define PUMP_ON_BUTTON 30
#define LED_TEST 2
// Variables
int buttonDebounce = 5;
// Button class
Bounce pumpSwitch = Bounce();
// Pin Setup
void setup() {
pinMode(LED_TEST, OUTPUT);
pinMode(PUMP_ON_BUTTON, INPUT);
pumpSwitch.attach(PUMP_ON_BUTTON);
pumpSwitch.interval(buttonDebounce);
pinMode(PUMP_POWER_PIN, OUTPUT);
digitalWriteFast(PUMP_POWER_PIN, LOW);
}
// Program
void loop() {
// Check if button pressed
pumpSwitch.update();
// Turn on pump and LED if pressed
digitalWriteFast(LED_TEST, HIGH);
digitalWriteFast(PUMP_POWER_PIN, HIGH);
delay(100);
// Turn off pump and LED
digitalWriteFast(LED_TEST, LOW);
digitalWriteFast(PUMP_POWER_PIN, LOW);
}
}

#### LowQCab

Joined Nov 6, 2012
1,308
Why are You using 2-Outputs to drive the FET ?
This is completely un-necessary.
They are marked High and Low,
what type of Output(s) are they configured to provide ?
Are they opposing each other ?
.
.
.

#### bertus

Joined Apr 5, 2008
21,667
Hello,

In there you will find this typical circuit:

The chip has sink and source outputs:

Bertus

#### ronsimpson

Joined Oct 7, 2019
1,630
The gate resistors are correct. One resistor is for turn on and the other is for turn off.

#### roboticsmick

Joined Oct 10, 2021
3
Why are You using 2-Outputs to drive the FET ?
This is completely un-necessary.
They are marked High and Low,
what type of Output(s) are they configured to provide ?
Are they opposing each other ?
.
.
.
This is how the example was laid out on the datasheet and I was using Designing Power MOSFET Circuits as a guide where they set the values the same.

I've tried changing the resistor values between 5 - 60 Ohms to change the current, but that doesn't seem to effect anything. It works with 5V, but I need it to work with 12V?

#### LowQCab

Joined Nov 6, 2012
1,308
You don't need a FET-Driver unless You are Switching at high-speeds.

Are You controlling the speed of the Pump with a PWM Scheme ?
or just switching it Off and On ?
.
.
.

#### ronsimpson

Joined Oct 7, 2019
1,630
The Gate Driver is a good idea because you can get 12V on the gate. Many micros now run at 3.3V or less and can not turn on a power mosfet.

I can not see why 12V or 7V does not work but 5V does. What all is powered by the 12V? There must be something happening what I can not see.