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Make sure you add a protection diode (cathode to plus) across the motor to suppress turn-off spikes that could zap the transistor.
Carl suggested earlier:
See the attached!
I have no clue how a microprocessor could have cost you $100?
All of your drawings still reflect a poor choice of MOSFET and yet you still persist, I fail to understand that? Using the correct MOSFET with the mentioned correct protection should be all you need. As to a DC SSR? Why? If you want isolation a few dollar opto coupler for the gate signal should work fine.
Just maybe if you would stop and listen to people you might stop cooking parts. If you don't understand when someone tells you something then ask for clarification.
Ron
You want your circuit to resemble the attached. The way you have it drawn the MOSFET Gate is shorted to ground. Also your U2, when it is turned on effectively becomes a 36 volt short to ground. The LED side of the opto will work fine with a fwd current of 10 mA and a fwd voltage of about 1.2 volts. That would be about a 380 ohm series resistor. I used 330 as a common off the shelf part. This is your opto coupler data sheet. It's actually a quad so you might want to rethink that.
There may be a few other errors, I did not really look close at the MOSFET data sheet. Getting late for me as I am up at about 3:30 AM so you have a good evening.
<EDIT> OK, now I get the part numbers. I saw your comment about multi-sim. That makes sense. You are only working with the parts in the library that you have. </EDIT>
Damn, one more thing. With this setup the motor will run when the PIC output line is low. Look closely at what happens.
Ron
You can buy dedicated MOSFET gate driver optoisolators and skip all this junk.
What voltage does it run at? Where is the 5 volts coming from?
You still have a few options. You can run with a Logic Level MOSFET like this one designed to run off a uC using a 5 volt gate for full on or you can run with a device like this. The problem with the latter being the maximum allowable voltage. Personally unless isolation is important I would just keep things simple and run with a MOSFET designed to run with a 5 volt gate voltage. However, your call on that note.
Ron
Most circuits do not work if their grounds are not connected togrether.
The spark you saw that caused damage was due to a wiring mistake.
Edit: Maybe the spark was the gate of the Mosfet being destroyed by the too high 36V then the 36V went into the output of the microcontroller.
A D1D40 solid state relay will work fine if you can afford one.
You don't know "how much voltage needed to close the switch" because you apparently didn't look at the data sheet (the data sheet link is on your referenced web page). If you look at that data sheet where is says INPUT SPECIFICATIONS you will see that the control voltage range is 3.5V-32V and the input current is 1.5mA @ 5V. It also shows a diagram of how to connect it.Well lets put the MOSFETs to the side one more time, and go back to the solid state relay idea, as I'm curious to how simple or complicated it would be to use one such as this for my application: D1D40: CRYDOM: Electromechanical
Would it be as simple as hooking my microprocessor to the inputs of the device, and hooking the motor connectors (36v) to the other side (output side) of the device? Or are additional components going to be needed? I see it states the input can support up to 32v, but what I do not see or know is, how much voltage is needed to close the switch or trigger the switch to close?
You don't know "how much voltage needed to close the switch" because you apparently didn't look at the data sheet (the data sheet link is on your referenced web page). If you look at that data sheet where is says INPUT SPECIFICATIONS you will see that the control voltage range is 3.5V-32V and the input current is 1.5mA @ 5V. It also shows a diagram of how to connect it.
Yes, you hook the uP to the inputs and the motor to the outputs with no common ground required.