UEGO temps

[Bernd Felsche]

Chad Clendening tapped away at the keyboard with:
> The UEGO heater controller circuit outputs a constant current
> UNTIL the preset max voltage is reached.  Then it limits the
> voltage to the limit ( 10.5 or so).  This allows it to slowly warm
> up - without cracking the ceramic.

> The constant voltage mode isn't by any means perfect, but sensing
> resistance of the circuit isn't the easiest thing to do in the
> analog world.  With a digital controller, this would be pretty
> easy.

You've done it now... throw away those analogue chains and impale
yourself on some digital spikes! :-)

I've spent a couple of nights working through this (on paper and in
the grey mush) and come up with the idea of [sound of fanfare]
"Direct Digital Lambda". (abbreviated "DDL" and pronounced "DiDiL")

Basically, it's using an MPU closely-coupled with the sensor to
drive the pump cell and heater as well as delivering calibrated
AFR output and select pieces of kitchen sink, if you so desire:
 http://members.iinet.net.au/~metapro/bernie/tech/EFI/vapour/DDL.html

If there aren't enough disclaimers on what's there; the schematic
shown is an incomplete circuit and there's no guarantee that it will
work for anything, let alone the sensor discussed on the page. I'm
CERTAIN that it won't work as shown.

But don't look at the _details_, look at the functional blocks and
their ostensible  functions.  I hope it generates some ideas and new
ways of looking at the problem.

> The control loop on this can be pretty slow, how fast will it
> really change temp?

Depends on heater power and the amount of heat gained from the
exhaust gas.

-- 
 /"\  Bernd Felsche - Innovative Reckoning, Perth, Western Australia
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