Ignition timing reference points

[Kalle Pihlajasaari]

Hi SMD,

>   Even the 'sealed' optical encoders can have problems.  One is on the end
> of an induction motor (for electric vehicles) and microscopic drops of oil
> can get in cause false edges.  A REAL pain.  We just have not had good
> experiences w/ them.

I think this would be a problem with glass disk encoders, with just 360
lines you could get the unit in a perforated disk so the oil would
not be a problem I think.  I must make enquiries again, been a while.

Cheers

> Some one said they are analog in nature (agreed) so he couldnt use them w/ a
> micro (here's where I disagree).  We use an Analog devices R2D converter
> (resolver to digital) that gives you a nice 10-14 bit word (depending on
> dynamic perf. required) giving absolute poistion.  Not too bad -> 0.35 to
> 0.02 degrees resolution.  (The R2D we use is about $60)

Yeah, they would work quite well.  The conversion has the problem that
you have to sample it and at those resolutions you will have missing
codes unless you sample real fast so you will be expending processor
time unless you have a parallel external magnitude comparator.

Nice thing though is the environmentally immune nature of the beasts.

Cheers
-- 
Kalle Pihlajasaari     kalle at data.co.za
Interface Products     Box 15775, Doornfontein, 2028, South Africa
+27 (11) 402-7750      Fax: +27 (11) 402-7751