Trouble with MCT2e driver

betwixt said:

It would probaby work with 1K, you could drop to 470 Ohms to be absolutely sure you have enough LED current. However, you have the optocouplers wired wrongly and they will not produce any output as shown. The MOSFETs probably want connecting differently as well, switching a capacitor across the supply wont achieve much.

I would drop the 10uF capacitor on the reset pin to 1uF or less, OR, add a diode, (cathode to VDD) across the 10K resistor. Otherwise you risk holding the MCLR pin high when the power is removed which could damage the PIC. You also need grounds on the regulators and a more reasonable value capacitor than 104F !

Why draw in .doc format, it's much easier to use a circuit drawing package. There are many free ones around, I recommend Kicad.

Brian.

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betwixt said:

There is nothing wrong with 1K in series with the gate as long as the PWM is fairly slow. The MOSFET has a fairly high gate to source capacitance which has to be charged and discharged through the resistor so as the speed increases, the rise and fall of gate voltage will become more gradual. However, in your design there will always be 12V across pins 4 and 5 of the MCT2E because one is connected to the 12V supply and the other is grounded!

Brian.

Click to expand...