BS2sx Ignition System

Archiver

I am building an ignition system for a 2 cylinder two stroke engine.
It is a MOSFET triggered coil, and I am using two optical sensors to
fire the MOSFETs, one for each cylinder. This leaves me with fixed
timing at all RPMs.

I am thinking of incorporating my BS2sx into the ignition box so that
I can have programmable advance/retard on the ignition. I would use
two optical sensors, just as I have now, but one would be a reference
mark and the other would count off degrees from the reference. If I
used 360 marks per rev, and figured the engine at a max RPM of 10k, I
would get 60kHz on the degree counter. The BS2sx is clocked at
50mHz, but only operates 10k instructions/sec. Other than cutting
the resolution on my timing wheel, anyone have a way of getting the
BS2sx of being able to adjust the timing to +/- 1 deg?

If I could put a lookup table in the Stamp and have it pass the
timing values to a timer/counter, it may work. The timer/counter
would have to count the incoming stream to find the RPM, but the
Stamp would have to monitor it to pass the correct advance/retard
value.

Am I trying to shoehorn the Stamp into a job it shouldn't do? Does
anyone know of a programmable microcontroller that can hande the
rates I am talking about?

Thanks
Kevin

Archiver

In a message dated 4/1/2003 1:55:05 PM Pacific Standard Time,
krwalsh@y... writes:

> Am I trying to shoehorn the Stamp into a job it shouldn't do? Does
> anyone know of a programmable microcontroller that can hande the
> rates I am talking about?
>
> Thanks
> Kevin
>

Kevin,

Parallax also sells an SX that you clock can easily clock at 50Mhz,
(20ns/instruction)
This thing is really fast! It can easily handle your speed requirement.

If you are up to the challenge this is the way to go. If you have a good
deal of programming experience then it's a breeze. But, even a dummy like me
who had no programming experience, learned how to use the basic stamp, then
moved on to the SX.

There is an initial investment. The SX key is about $180!!!! But the SX chip
and resonator is less than $10. Depending on how often you do these kind of
projects, you obviously must weigh the cost of initail investment verses the
long term savings.

Somebody previously made a very good analogy of the comparison between the
Basic Stamp and this SX. (excluding cost).

Assuming your programming skills are somewhere between a beginner to
intermidiate .......For almost any simple to moderate project, you can get
the basic stamp up and running in one evening. Sometimes to do the same with
the SX will take you 4 times as long (or more) to write code that will do the
same function as the Basic Stamp.

The SX programming is not as easy as the Basic Stamp. It is programmed in
Assembly language. But, with the Parallax SX key and software, it has a nice
Debug window.


<A HREF="http://www.parallax.com/sx/index.asp">Parallax: SX Tools</A>

Hope this helps.

Ken


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