Steve Anderson wrote:Using a MOSFET is a good move, though I doubt you notice any real difference in LED brightness just because the voltage loss has gone from 1.2V down to less than half that.
True, but it might be the difference between being able to run 3 LEDs in series and only 2. In any case I'm moving to a higher voltage source for rev 2.
Steve Anderson wrote:I assume you have a series resistor in the base lead for the TIP device, with a MOSFET that can be removed. i.e. zero Ohms.
Yes, 16 ohms at the moment, tailored to my original 26V LED matrix - I will/have remove/d in the design for rev 2.
Correction: I have a 16 ohm resistor in series with the emitter of the TIP122. The base is connected directly to the Arduino pin. I'm pretty sure we worked out in the earlier discussions on the LED matrix circuit that this was OK.
Steve Anderson wrote:I would investigate why this happened, not just hope it doesn't return.
How "what" happened? ............ lol. OK, so I don't really have much of an idea where to even start with this. I replaced the IRL540 same issue seen. There's the component, and then it's connected to the Arduino - with a 10K resistor from the PWM input to ground (this is optional and to cure the 'floating' state of the pin possibly causing motor spin. I now think this is way overkill anyway, but it's there nonetheless). I can't desolder/replace the Arduino - way too much work. So, not really sure I want to tackle this issue. I'm moving on with a completely new/revamped circuitboard so .. mmmh....