Hi!!
Please correct if I am wrong. The scheme above (attached) is breaking the Opto isolation
Right?
If so, whcih I am quite sure, how do I feed the IRL540 gate since 24V is too much.
Eduardo
The IRL 540 and IRF 540 with the IRF 540 shown in your drawing are not the same. Look at the data sheet for each. The IRL 540 is a logic level MOSFET which means a 5 volt signal on the Gate will turn it on. However, as drawn if you turn on the MOSFET you have a nice 24 volt path to ground so expect a short period of smoke.
What exactly are you trying to do? If you use a IRL 540 it can be directly driven by an Arduino output or any 5 volt level on the gate. You also want a resistor, maybe 10K between the Gate and Ground. Again, please explain what your goal is?
Ron
Please correct if I am wrong. The scheme above (attached) is breaking the Opto isolation
Right?
Right.
Yes, pin 6 of the opto needs to come from the 24V with a current limit resistor, and Gnds need to be separate signals also.
You should also add a resistor from Gate to Gnd, otherwise once high, there is nothing to bring the gate low to turn off the MOSFET.
Probably should limit the Gate to 10 or 12V also. 10V usually turns a MOSFET fully on, while many are not rated to have Vgs exceed 20V.
Make a voltage divider with the opto coupler, so the gate only ever sees 0/12volt.
1k resistor between pin4 and mosfet ground (source).
1k resistor between pin5 and 24volt.
Gate directly to pin5 of the opto.
220 ohm between Arduino pin and anode opto LED
Cathode LED to Arduino ground.
Leo..
If you just want to use a 4N35 optocoupler with an Arduino give this a read and a look.
That pretty much covers it. Note how the Source and Drain of the MOSFET are configured. Your MOSFET has no load?
Ron
What if to use only the MOSFET. Am I isolated from Arduino? Or safe enough
Like this
Eduardo
I think so, but you need a Logic Level MOSFET, one that will turn on fully with 5V, vs 10V for a standard MOSFET.
A great example:
https://www.digikey.com/product-detail/en/alpha-omega-semiconductor-inc/AOD514/785-1357-1-ND/3060919
Is this suite too?
eduardo_inglez:
Is this suite too?
Yes, I have used it. If the load is a motor you may want to place a diode across it, cathode side to + to act as a flyback diode.
Long as your motor current does not exceed your MOSFET continous current rating.
Ron
Many tks for all!!!
Hi,
This may be the schematic you need, it was drawn for a different project but conveys the idea.
R2 and R3 will have to be adjusted and/or a 12V zener added to keep the gate voltage down to within spec.
Tom...
eduardo_inglez:
Hi Tom. Like that:
Yes, must edit that graphic, needs the back EMF diode.
Thanks.. Tom....
Basically the same as I recommended in post#5, with R5 and opto transistor swapped.
Which is electrically the same.
Leo..