Best stradegy to protect arduino when using MOSFETs?

I will be using a mosfet to switch on/off a 100w LED. I have been reading up on mosfets and keep seeing where folks have their Arduino destroyed from a mosfet failure. Of course, I want to reduce the risk of that happening.

What strategy would be best to protect the Arduino?

As of now, I'm contemplating using a separate 5v source to power the gate. And using an optoisolator to turn that 5v source on and off.

Not good enough?
A better method?

Opto-coupler and separate 5V supply is good - note typical opto-isolators are not fast enough for PWM,
in which case use a MOSFET gate driver chip and add 10k resistor in series with its input to protect Arduino
from the driver burning out.

MarkT:
Opto-coupler and separate 5V supply is good - note typical opto-isolators are not fast enough for PWM,
in which case use a MOSFET gate driver chip and add 10k resistor in series with its input to protect Arduino
from the driver burning out.

I appreciate your reply. I don't intend to use PWM at this point. And have no plans for it in the foreseeable future. But that is good info to know in case plans change.

Yes, opto couplers typically(*) take several us to switch off, which leads to lots of switching losses
driving a high power MOSFET (typical MOSFET switching times are 100ns).

(*) There are faster opto couplers designed for logic speeds though.

Hi,

What is your source of power for the 100 watt LED?

John

MarkT:
Yes, opto couplers typically(*) take several us to switch off, which leads to lots of switching losses
driving a high power MOSFET (typical MOSFET switching times are 100ns).

(*) There are faster opto couplers designed for logic speeds though.

Thanks again!

JohnRob:
Hi,

What is your source of power for the 100 watt LED?

John

For the time being, a DC power supply with a cc boost converter.

That will be a future project though. Once I learn more, I might (keyword, might) build my own DC supply. But I have a lot to learn/relearn before I would feel comfortable tackling that. My eventual goal, just for the sense of accomplishment and learning, is to DIY the entire project, possibly including a micro-controller. I know that it would be easier (and probably cheaper in the long run) to just buy off the shelf products. But that's not the point.

And if I decide not to build a power supply, I'll most likely switch to a Meanwell supply.

And if I decide not to build a power supply, I'll most likely switch to a Meanwell supply.

If you get a dimmable constant-current LED power supply the diming is controlled by a 0-10V DC control-voltage or by 10V PWM.

That's a very low-current control signal and it only requires a low-power transistor or MOSFET (and a ~10V source) so even if the transistor/MOSFET shorts-out it won't kill your Arduino (as long as the driver circuit is designed properly :wink: ).

That will be a future project though. Once I learn more, I might (keyword, might) build my own DC supply.

I have an engineering degree and many years of experience (although I'm not a power supply engineer). I've built lots of little DC power supplies for my hobby projects, but I would NOT attempt to build a constant-current power supply for a 100W LED (unless I had a really good reason).

DVDdoug:
If you get a dimmable constant-current LED power supply the diming is controlled by a 0-10V DC control-voltage or by 10V PWM.

That's a very low-current control signal and it only requires a low-power transistor or MOSFET (and a ~10V source) so even if the transistor/MOSFET shorts-out it won't kill your Arduino (as long as the driver circuit is designed properly :wink: ).

I have an engineering degree and many years of experience (although I'm not a power supply engineer). I've built lots of little DC power supplies for my hobby projects, but I would NOT attempt to build a constant-current power supply for a 100W LED (unless I had a really good reason).

Thank you. I'll look into that option for certain. Dimmable isn't really necessary to the project. But having that 10v control could have serious benefits for someone lacking experience/knowledge. Such as myself!

DangerToMyself:
I will be using a mosfet to switch on/off a 100w LED. I have been reading up on mosfets and keep seeing where folks have their Arduino destroyed from a mosfet failure. Of course, I want to reduce the risk of that happening.

Can you link to an example? I have a hard time seeing that happen unless the gate insulation is blown. That's more likely to happen through improper handling than any circuit issue.

Jiggy-Ninja:
Can you link to an example? I have a hard time seeing that happen unless the gate insulation is blown. That's more likely to happen through improper handling than any circuit issue.

https://electronics.stackexchange.com/questions/33400/my-mosfet-operated-solenoid-circuit-destroys-my-arduino-inputs

That is just one of a few that I saw.

Adding a zener between gate and source is a common and good way to protect the gate from over-voltage,
since zener/avalanche breakdown is fast.

I have a hard time seeing that happen unless the gate insulation is blown. That's more likely to happen through improper handling than any circuit issue.

If only that were true - over-voltage on the gate can be caused by ground-bounce affecting the source,
or via gate-drain capacitance with high dV/dt on the drain and various other mechanisms. With high power
circuitry you should be thinking "good layout and decoupling, use a proper gate driver, add a zener on the gate"
as the first precautions against popping your MOSFETs.

Hi,

Your consideration of a Opto isolator will certainly protect the arduino and would be perfectly fine.

However it is more complex than needed.

If you goal is to simply protect the Arduino you could:

  1. add a 5k resistor in series with the gate to the Arduino.
  2. add a 100 ohm resistor between the Arduino ground and the power ground.
  3. Be sure the grounds are wired like:
    a) Arduino stuff on one side (power supply, Arduino board etc)
    b) The power stuff on the other side (LED power, MosFet Source etc)
    c) connect the two sides with the 100 ohm resistor.

The reason this works is the MosFet Gate required virtually no power so the 5k (value ) will protect the Arduino in case the MosFet Fails.

Note: The failure mode of a power MosFet is shorted, sometimes D-S, sometimes D-G-S.

In any case, its important to layout and wire your system so there are no paths that rely on a wire being intact to prevent a failure. In other words the grounds and supplies should be that any connection can become open and the Arduino would still be protected.

Good luck

John

That dude tried to switch 650mA with a tiny TO-92 mosfet with >1.5ohm Rds(on).
It must have been sizzling hot before it went up in smoke.
Not strange it took out the pin in the process.

I already advised a Meanwell CC driver in your duplicate post.
https://forum.arduino.cc/index.php?topic=489640.0
Leo..

Wawa:
That dude tried to switch 650mA with a tiny TO-92 mosfet with >1.5ohm Rds(on).
It must have been sizzling hot before it went up in smoke.
Not strange it took out the pin in the process.

I already advised a Meanwell CC driver in your duplicate post.
Is there a safe reliable relay to use with Arduino - Motors, Mechanics, Power and CNC - Arduino Forum
Leo..

Thank you! If you have a look at post 5 above, you'll see where I mention the possibility of eventually going to a Mean well. And with DVDdoug's advice, it's more of probability than a possibility.

As a side note, I fail to see how asking about a reliable relay and asking how to protect an Arduino from mosfet failure are "duplicate". But ok. Sort of like calling "Why is the sky blue?" and "How many stars are there?" duplicate questions.

My thanks go out to all that contributed. I have and will continue to learn from you folks. I'll take those suggestions and read up on them. Thnks again.