I am designing my first Arduino project using the Arduino mini pro 5v (previously i have used mega or UNO).
what i am unsure on is where to start with the power input stage.
i have a 12vDC switch mode supply
this powers the arduino (via raw input)
a 12V led strips (via FETS and PWM)
a big easy drive stepper motor controller.
all of this is on a single proto board. (with pin headers etc)
I have a diode in series with the Arduino to protect it from rev voltage (the big easy drive has one on board)
nothing protects the FETs as i need 12v from my outputs (do not want the volt drop over a diode to lower my output voltage)
however i am interested to hear thoughts on capacitors for current smoothing etc and if anyone has some basic guidelines on how power should come into a circuit?
am i missing anything vital for stable performance?
is there a better way to protect from rev voltage?
do i need capacitors for smoothing?
reverse voltage is mainly to protect against miss wiring on site, as these units will be made by me and then installed by someone else with screw terminals for power its easy for them to get the polarity reversed.
am i missing anything vital for stable performance?
is there a better way to protect from rev voltage?
do i need capacitors for smoothing?
As G_M noted, you have to have bypass [typically small ceramic] and reservoir
[typically largish electrolytic] capacitors on your pcb for filtering and stability.
Also, in regards "is there a better way to protect from rev voltage?", once you
have the diode installed in the Vin line, a MUCH MUCH bigger worry is protection
for all the I/O pins on the Arduino.
Your field guys will likely [with non-trivial probability] be miswiring 12V straight into
the 5V I/O pins with regularity, so you should think about protection on "all" i/O
pins. Typically, a small series-R of about 220-330 ohms will go a long way towards
saving the Arduino's little butt, but for extreme environments, you'll need even more
protection. See ruggedcircuits.com [I think].