MOSFET driver simulates but does not work in real life

Discussion in 'General Electronics Chat' started by electrophile, Feb 2, 2016.

  1. electrophile

    Thread Starter Member

    Aug 30, 2013
    98
    1
    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?
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    Haven't you by accident swapped the drain pin with the source pine ?
     
  3. dl324

    Distinguished Member

    Mar 30, 2015
    3,211
    619
    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.
     
  4. #12

    Expert

    Nov 30, 2010
    16,248
    6,745
    I agree. Your schematic is good. It must be an assembly problem.
     
  5. Bordodynov

    Active Member

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

    Thread Starter Member

    Aug 30, 2013
    98
    1
    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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