Old 486 Board for ECU??

[Garfield Willis]

On Tue, 09 May 2000 17:04:41 -0400, Chris Conlon <synchris at ricochet.net>
wrote:

>I have a very off topic question about this. Somewhere in this thread
>you had mentioned lambda sensor heater control, in the context of
>something that needed PWM. I was under the impression that one just
>fed the heater +12v (maybe w/ballast resistor) and let it cook.
>
>Specifically I'm thinking of the common OE type HEGO sensors, nothing
>fancy. I do remember reading that the heater control requirements were
>a bit trickier for the wide band units.

I've not been a contributor to this thread, but there's the issue of
whether the heater has a positive or negative coefficient of R; if
positive, there very well could be some controlling required. If
negative, like the NTK sensors, even when used in a wide-band
measurement application, they don't require the heater current to be
overtly controlled, since the neg. temp coeff. makes them somewhat
self-regulating, as well as the current-pump technique itself being
relatively insensitive to temp changes.

The Bosch LSM-11 heated 4-wire "wider-band" sensor's heater DOES have a
negative tempco, and certainly when used in a measurement application,
has to have some very robust temperature controls. These were originally
marketed simply as "lead-tolerant" HEGOs, and when used in an ECU-O2
feedback switching-type application, I don't really know if the Bosch
ECUs did anything for heater current control. Anyone?

I too was under the impression that with most OEM HEGOs, the heater is
just connectes to +BATT.

Gar


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