MOSFET driver simulates but does not work in real life

Thread Starter

electrophile

Joined Aug 30, 2013
126
Attached here is a schematic for a n-mosfet driver (along with the LTSpice schematic). To simulate the load I have an LED with a resistor. The 4N25 opto coupler is controlled through an Arduino (V3 in the schematic). Now this simulates just fine in LTSpice but when I assembled everything on my breadboard it doesn't work. The LED stays on through out. The Arduino code just switches on and off a particular pin at intervals of 2 seconds. Any ideas?
 

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dl324

Joined Mar 30, 2015
9,581
Are you sure you have the MOSFET connected correctly? Measure the voltage on the drain when the LED should be off. If it's 0.7V, you have the S/D reversed.
 

Bordodynov

Joined May 20, 2015
2,469
I had a similar problem when soldering confused sometimes collector and emitter of the optocoupler (PCB solder wires to the connector).
 

Thread Starter

electrophile

Joined Aug 30, 2013
126
Thanks folks! I had switched the D and S. Also some of the wiring from the Arduino was bad and once I switched them out and set the MOSFET right, everything worked as expected.
 
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