I am using my arduino to read various signals from a motorcycle electrical system. I had been using a 1M/470K voltage divider to bring the voltage down below 5V but I was getting ignition interference.
I followed up on a suggestion that I use a 10K resistor and a zener but I find that the zeners I bought want like 20ma current - did I just pick the wron ones? I got, for example, 1N5228Bs http://www.datasheetcatalog.org/datasheet/HitachiSemiconductor/mXwuzrw.pdf which are tested at 20ma and which don't seem to regulate with a 10K resistor.
I don't feel like I can afford to draw 20ma from some of these circuits - it would start lighting my LED idiot lights for example. Are there zeners with lower currents? Am I missing something else?