Optocoupler and N Mosfet Schematic

Projects General Guidance
1

Hello everyone.
I am wanting to use a 4n35 type optocoupler to control an IRF730 Mosfet.
The idea of ​​this circuit is to activate a 0.5 ohm nichrome resistor so that it heats up and melts a wire.
In the schematic I am using a 0 - 3.3v square signal to activate the octocoupler and 6v sources for the nichrome resistor and the output of the octocoupler to the mosfet gate.
I used a light to simulate the charge instead of the nichrome resistor. U1 y L1 6V

My question is if the schematic is correct and will work, and if the resistors used are appropriate.

optocopler
optocopler854×494 7.27 KB

I attach the datasheets of the components

2

  • Suggest you use an IRF3708 MOSFET

  • R2 can be larger, 6.8k to 10k

  • R1 can be 220R

  • If you are using 2 power supplies, GND Pin #2 of the 4N35 can be isolated from the 6V GND

3

Can your MCU (whichever it is) output pin safely source 20mA?

4

Yes it can, since it is a Regulable source.

5

Have an update. Do you think a R 10ohm will support for disipate power? Now the mosfet is just with the nicrome wire load and heat a lot. Want to put the R10ohm for reduce the voltage on the Drain-Source and have less temperature there.

image
image276×517 3.69 KB

I have a 10 ohm 1/4w resistor

6

Are you still using the IRF730? Did you look at the IRF3708 @LarryD recommended?

With current and voltage you get watts, watts is heat here and the latter MOSFET would take a smaller fraction of the total heat being dissipated by the wire, any extra resistors in series and the MOSFET itself.

Otherwise, if the current is within the MOSFETs specifications, and you are properly removing heat from it if there is that much, I see no real problem other than wasted heat.

have a 10 ohm 1/4w resistor

Hmm, too lazy to calculate. Won't you be asking that resistor to get a bit hotter than it wants to?

What does Ohm's Law tell you?

a7