usafmx wrote:Thanks for both inputs!
I attempted to use a passive noise filter gotten at a car stereo shop (looked like a square transformer...not sure how many loops). negative results. I may not have rigged it correctly (hard to know as no data sheet available).
Usually three legs - one to 12V+, one to feed power to the radio <errr - device>, one to the common ground (usually black). Normally they are just a tiny plastic box with capacitor and transformer inside.
usafmx wrote:ModemJunki, regarding grounding of the Arduino...isn't the board grounded via the negative of the power plug?
What is the rational for grounding the Arduino to the chassis?? To manage the noise? where should i connect the chassis ground on the Arduino?
Adding grounds to the <device> gives it cleaner power. This is partly old wives tales (go to ebay and search for "ground kit" in or similar in automotive) but partly based on good practice installing car audio and radio. Sometimes improving the grounds elsewhere (ignition system, charging system) fixes interference problems.
I would tie the Arduino ground bus to the physically nearest place on the car body and only run the 12v+ line to it. Maybe even use a shielded cable for the power and connect the shield to ground.
Or - try powering it with a 5v adapter (generic USB cellphone charger). Worth a try!
I think it's better to first try and clean up the power than to use the diode as a quick fix, though I do think the diode should be in the design (but I don't know electronics at that level, so I don't know what could/will happen to your Hall signal!). I know that over at http://www.the12volt.com/
there would be scolding for not diode protecting your car from your <device>.
I have a vested interest in this topic - I will be putting an Arduino in my car in when the weather warms up, and I'm still thinking of ways to integrate more functions into my idea (but I have more ideas than time). My vehicle has full electronic cabin controls and all the buttons simply momentary to ground so any control is fair game. Adafruit has a lovely current sensor I could possibly use to count pulses from the long-range locking function.....
my birthday is today...maybe i will treat myself to a long overdue, low-cost oscilloscope and signal generator (with spousal permission of course)