Ok - I think that the chip was toast - no biggie... I bought a new board and ordered a few 328p chips from digi (the new board because idk what else is damaged on my current one, and if it is not damaged - to program the new chips via ISP if/when I fry them again).
So now I wanted to get into another question I had regarding my transistors. My specific project is a series hybrid gasoline/electric UAV/RC plane
Here is a thread in another forum detailing the project if you are interested: http://fpvlab.com/forums/showthread.php?11355-The-flying-Prius
The arduino uno actually manages the IC engine's throttle for the onboard generator (spins a brushless motor connected to a 3-phase rectifier - voltage is filtered through huge caps and sent to an ESC which drives another electric motor which will fly the plane) using Bretts PID library (thanks for that btw....)
I have batteries in the aircraft for backup/on-demand vibration-free operation, and all power lines are a 1-way street (I am using high current diodes to prevent battery charging directly from the generator).
The transistor stuff is all about trying control charge current going into the battery. I want to keep it simple - and it was suggested that I use the IC engine to control charge current - and while possible - I think is improbable due to real-world limitations.
My idea was to have the rectified generator voltage go through a logic-level FET (http://www.digikey.com/product-detail/en/RSY160P05TL/RSY160P05TLTR-ND/2075693
) and into the battery. I want to hook the gate of the FET DIRECTLY to a PWM port of the ardu (thats why I was playing with cheap transistors just to refresh my mind about the electronics class I took 6 years ago as an undergrad...).
In practice (for now) - I do not care about constant current... I just want to set the PWM duty cycle so that when the battery is fully drained - it will not see more than 5 amps of charge current. I understand that as the battery fills, the duty cycle would have to be adjusted to keep current constant, and I have some ideas on how to do that... but for now I don't care.
All I am wondering is the following: @ ~500 Hz switching frequency, is 20-40 mA coming from the ardu into the gate of my FET is going to be sufficient to avoid huge switching losses at a load of 5 amps (I will tune this with a current sensor)? Or should I still use some kind of driver despite the FET being logic level?
If this matters at all - generator voltage is currently "maintained" at around 24.5 volts and will be charging a 6-cell lipo (obviously not fully charging).