Very hot mosfet when powering an led strip

Question

I'm basically following this instructable which is using an arduino to control an rgb led strip. I have wired it up exactly as shown, although I didn't use a breadboard i just soldered everything.

I'm using an old laptop power supply that's 12v 5.83a, and for the mosfet I'm using irf530n. I've noticed that when red is full power the mosfet that's connected to the red led gets really hot after a few minutes of being on. It seems to only be affecting the red one, even if i have it on full white only the red one is hot. The other two barely get warm.

Are the mosfets supposed to get that hot? Why does it only get hot on the red side? Are there mosfets out there that are better suited for this application? Are there any ways to reduce the heat?

Thanks for any help!

Edited to add a schematic:

Answer 1

Red LEDs have a much lower voltage drop than other colors so in order to compensate, the mosfet is having to drop a significantly higher amount of voltage/power.

Red LEDs usually have a drop of 1.8 V while Blue and green are up into the 2.5-3.3 range generally. This means that the Red mosfet will have to drop about an extra volt at whatever current you're running it at. Power wasted is V*I.

The way to get around this would be to have a switching regulator that brings the voltage down closer to the range you're after for the Red LED and then power it that way. Otherwise, you'll always end up with wasted power and more wasted power from the red LED channel.

If you don't want your red mosfet getting hot, you could determine how much current and voltage it is dropping compared to the others and then add a series power resistor to absorb some of the power for the Red LED. In this way, you distribute the heat between the resistor and the mosfet driving the red LED.

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EDIT:
Doxy has pointed out that there's already a constant current driver/resistor on each LED so I suspect that the problem is actually that they're using the same resistors for all colors of LEDs. This results in a higher voltage dropping across the same value resistor which means an increase in current for the red LED. Then your mosfet switcher is actually always seeing a larger current than the others. The easiest fix here is still as I mentioned originally. Add another resistor to the red LED path to balance out the current between all of the colors.

Alternately, you may try reducing the duty cycle on the Red LED's and see if that alleviates the problem.

It could be a part issue. In that case, swap the MOSFET's around between say Red and Blue and see if the Red MOSFET still heats up the worst.

Otherwise, if these three things don't help you out, without more diagnostic information on the circuit, there's not much anyone can tell you.

Answer 2

just see your maximal power output for your Arduino. It is possible, that you are sourcing too many mili-amps from your Arduino, so you have lower voltage on some pins. Since on Gate of MOSFET is lower voltage, its not fully open, have bigger resistance and warm more. Therefore it is very usual to put resistor between PWM Pin of Arduino and Gate of MOSFET (min 120 Ohm, typically 200-250 Ohms, depending on which arduiono do you have also 500 Ohms suits).

Also try to exchange MOSFETs, because one can have thicker capacitor layer so it will need more volts (after exchange you will see, it heats by another color).

I also find that potenciometers are not so good while it has on "0" also 0 Ohms (or 10 nano-Ohms) that means all the current from source is sinking to Arduino. Imagine, there is also limit for that, you can sink only 150 mili-amps to Arduino on one port. That means at least 33 Ohms between source of power and arduino. So maybe your analog inputs are burned.

https://startingelectronics.org/articles/arduino/measuring-voltage-with-arduino/