MOSFET questions

Other Hardware General Electronics
1

Hello everyone. I apologize if this is the wrong section to post this.

I'm working on a project where I am trying to regulate the temperature of this heating pad (Heating Pad - 5x10cm - COM-11288 - SparkFun Electronics). I am using a arduino uno, a mosfet, and a 12 [V] DC power supply to power the pad.

I initially bought a irf510 mosfet and tried using that in the following setup.

I realized that the irf510 was not being turned on fully by the arduino's 5V output. I not sure what mosfet I should get instead. I tried looking through the datasheets and was not sure what spec I need to check to make sure that the arduino's output pin can switch on the mosfet.

I want to be able to turn on and off the heating pad. I will have a temperature sensor connected to the arduino and depending on the reading I will switch the pad on or off.

My questions are:

  1. Which mosfet should I buy? I found the list of nte logic level mosfets (nte 2980,2981,2984,2985,2986,2987). I'm not sure if these would work and if so which would be the best for my application.

  2. If I use the pwm function on the arduino to the gate of the mosfet will the heating pad be given less current therefore lower in temperature?

  3. Is a relay better suited for this project?

Thanks in advance. I am quite the beginner in electronics so if I was unclear on anything please call me out and I will try my best to elaborate.

2

IRL540

3

AOI514

4

The heating pad is rated at 5volt, and you're putting 12volt on it?

Your 1A supply might collapse with a 6.5ohm load.

Sparkfun also has a logic fet.

Leo..

5

Why use a FET with 7x the Rds and at twice the cost?

6

Hi,
If you look here;

https://learn.sparkfun.com/tutorials/heating-pad-hand-warmer-blanket?_ga=1.39009507.1995039422.1426841022

You will find an example of how to use and program for the heat pad.
The sketch is for LILYPAD but should port to UNO easily.

Tom..... :slight_smile:

7

  1. Logic level MOSFET with a low enough Rds(on) for your load - this you calculate
    since power dissipation = I-squared-R

  2. PWM will get you reduced average power. Add a 150 ohm gate resistor between
    the Arduino pin and MOSFET to limit pin current and add a 10k resistor between gate
    and source to turn the MOSFET off when the Arduino isn't active.

  3. Depends on the relay and what you mean by "better". Relays can't do PWM, are
    larger, make audible clicks, require a transistor to drive them anyway....