I am planning a project that will be standalone Arduino (just the bare bones atmega, crystal etc). I plan on powering it from the vehicle 12V. I will also be using a 7805/2940 to regulate the 12V down to 5 for the chip. What I would like to do is this:
12V vehicle to: - Regulated to 5V for arduino. - Arduino controls MOSFET (IRF 530’s) to power LEDs from vehicle 12V
What I also would like to do is possibly have a capacitor
inline (in parallel) to provide some residual power to both the arduino and LEDs to allow for a graceful ramp down (as opposed to just turning off). The arduino would be used to simply control PWM values (0-255) to a MOSFET that would control the LED brightness. However, both the Arduino and LEDs would need some sort of residual ‘backup’ power for a few seconds after the car ignition is turned off.
Is it possible to do this by adding a capacitor
inline (in parallel) to store some power? I could then do something to detect when the main 12 has dropped to 0 and then trigger a shutdown while the cap provides power to both the Arduino and the LEDs? I am thinking like 3 seconds of residual juice here. What sort of circuit would satisfy this?
Edit: current draw would be less than 300 mA