Best resistor value to stabilize PWM pin going to transistor

[Werner]

Hi Guys, In playing around with PWM I have my output pin going to a power transistor and found that I really needed a resistor on the PWM pin going to ground in order to stabilize the transistor/PWM. I put my resistance substitution box on the pin/ground and it seems like 470ohm will do nicely. I just wondered if you Guys have also found this to work well. One other thing I noticed is that on an LED strip light I have hooked up to the output of the transistor, that only pulls about .5A I get a little leakage out of the transistor even when duty cycle is 0. It is very sensitive just a matter of touching a few of my jumpers can get it to point where the LEDs appear to be totally off instead of very low glow/on. I suppose I could just add a small resistor to the transistor output to ground but just wondered if anyone had any thoughts on this phenomenon.
Have a great day!
Werner

[brandonb]

what are you using for a transistor?

[Werner]

Hi Brandon, Thanks for the reply Buddy! I have been playing with two: BUZ101S and BUK9535. Both act very similar.
Have a great evening Buddy!
Werner

[brandonb]

thats weird, usually as you know N mosfets requred a pull down resistor from gate to ground of about 10k, but since your using the pic it shouldnt need one because your sinking the gate charge when pulsewidth is low discharging the gate to turn it off, i've run into stuff like this in past non pic projects, the scope is your best friend, i've seen issues of power noise cause weird things too, i usually place test caps in key areas to see the effect on the gate drive signal, im not really pictureing whats going on just throwing a couple things out there since i cant visualize it

[Werner]

Hey Brandon, I started thinking yeah that is weird so I decided to try a 5k pot and it worked great. It looks like the 1k pot was not coming all the way down 0 ohm? All the way down it was still showing 2ohm. Now it works great!
Thanks again Buddy!
Werner