Zener Minimum Current

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?

You could probably run that zener at 10mA maybe even 5mA.

Rather than a zener take a look at voltage references. They will be a lot more expensive but run at much lower currents. The TI LM236 is one example. The TI REF1112 has a current range of 1uA to 5mA but is over $2. Also checkout National Semiconductor.

(* jcl *)

Thanks. The LM236 is an 8 pin dip and I need something physically small!

I've given up and gone back to my voltage dividers for my next iteration.

It’s also in a TO-92 (LM236LP-2-5). Not as small as an upright zener but not too big.

Most of the lower cost references are available in SOT23, SOIC and TO-92.

(* jcl *)