The only problem with this is that if the microcontroller or optocoupler fails the mosfet stays on, but 5V failure means mosfet = off through 10k resistor. H11G3, HIGH VOLTAGE DARLINGTON OUTPUT OPTICALLY COUPLED ISOLATOR 6DIP.
if the transistor is on, the Vgs is = transistor Vforward? or about 0.7V? shutting off the mosftet since Vgsth is 2-2.6V. 4N25 OptoCoupler Optoisolator DIP IC - 4N25 - OptoCouplers - DataSheet: 4N35.pdf 4N35 is an optocoupler integrated circuit in which an infrared emitter.477mA, giving about 4.78 V to the gate once charged, activating the mosfet. If the transistor is off, the circuit is a voltage divider, 470 + 10000.I have thought about the common emitter config, and so far have come up with this schematic (attached). I put the R15 100 ohm resistor to limit the gate charge current, as to limit the ‘surge’ in the optocoupler transistor. 4N35 optocoupler can be used for variety of general purpose requirements in electronic circuits. 4.3 volts accross the resistor, ( 4.3V/470ohm) = 9.1mA. Replacement and Equivalent Part Numbers: 4N35 replacement and equivalent optocouplers are 4N36, 4N37, 4N25, 4N26, 4N28, PC816, PC817, 4N27, 4N36 & H11Ax series. The 470ohm resistor is to limit the current through the transistor to about 10mA or arounds there.
When the optocoupler transistor is on, the mosfet gate charges through R15 and will quickly gain full charge and have no current, meaning we will have (5 - Vforward transistor), ( 5 - 0.7V) = 4.3V or so on the gate, Correct?
When the optocoupler transistor is off, the gate of the mosfet goes to ground, through the 2 resistors, shutting it off, so power loss on the 5V or uC failure means mosfet = off. The reason I did the schematic that way (correct me if I am wrong I am still new at this)
Opto-coupler is an electronic component that transfers electrical signals between two isolated. I think it would be equivalent to the one I put in my schematic, except for the base. Optocoupler: Its Types and Various Application in DC/AC Circuits. The optocoupler I am going to use is a PS2501-4A, 16 pin, 4 channels.The mosfets I am going to use are similar but not the one on the schematic: Either FQP30N06L or AOI518 ( both logic level N channel, 2.6V max Vgs(th) ) Shop (Pack of 30 Pieces) MCIGICM 4n25 optocoupler Optoisolator Transistor 1 Channel 6-DIP online at best prices at desertcart - the best international. 1 2 nc3 4 6 Vcc R L Figure 4.34: 4N25 optical isolator (4.5.1 SONALERTS, BEEPERS, AND BUZZERS In Figure 4.35, we show several circuits used.