On Bench ECMs
garfield at pilgrimhouse.com
garfield at pilgrimhouse.com
Sat Mar 28 04:20:59 GMT 1998
On Fri, 27 Mar 1998 12:56:53 -0500, "Bruce Plecan" <nacelp at bright.net>
wrote:
>For doing this ecm testing on bench I need to come up with a
>0-4,000 pulse/min 50% PWM for the speedo, 0-6000 rpm
>V-8 tach signal, and something like a O2 swing...
>Would anyone have something like that hanging around/whip
>up a 555 schematic for me?. Sure be quicker than me
>trying to figure it out. Can use a audio transformer for Pick
>up coil input right?..
Best bet is to print out a copy of National's 555 datasheet. Lots of
examples, and graphs. Better than giving a single schematic. There ARE
examples of 50% duty cycle oscillators, etc. The O2 Rollercoaster curve
is not so cook-bookish; you might wanna wait a couple weeks until I or
someone else pops for that one. We gotta do it, so it's just a matter of
time. I'd like to do a log-linear approx. so the "bicycle crank" is
shaped correctly, which I think will take 3 op-amps, one for the center
steep linear region around stoich, and one for each log-leg of rich and
lean. Don't wanna confuse some picky ECU with something unfamiliar, ya
know. Meanwhile, this should keep you busy:
www.national.com/ds/LM/LM555.pdf
This is the standard document on 555 & applications.
>Cheers Bruce Wonder how many little black dodaads will
> loose their smoke over this
Their life-force (smoke) is in your hands. Conduct yourself wisely. Heh.
Gar
P.S. What's that about an audio transformer for the pickup coil? Ya lost
me. You mean take a pulse train from a 555 and feed it through an audio
transformer to create the appearance of a mag pickup sensor? I dunno, is
that common practice? Hmm, sounds good ta me, but a simple RC
differentiator of a narrow pulse might do just as well? (it'd have the
pos & neg blips, with a zero crossing betwixt). I dunno, I got a timing
wheel and a mag pickup on me bench, so I don't have to fake it (thanks
JAC!).
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