WB O2 Circuit Comments

[rr]

Timothy J Burgess wrote:

> Greetings and congratulations on designing an extremely useful tuning aid -
> I look forward to using it!  I have a few comments regarding the design:
>
> Change R1 to R4 in the note on page 1.

Yes.

>
> What is the value of the calR pot?

Ah, this one's easy! The resistor is included with every sensor. Note
that the connector housing has 5 wires but 7 pins. The two pins
without wires is the calibration resistor. No polarity, just wire it in.
Just don't switch CalR's between sensors. They are matched to
the sensor they came with.

>
>
> Under what conditions should the heater Imax to be reduced from 1.5 A to
> 1.45 A?

When the warm up time is too short. Might start w/o a trim resistor and
measure the warm up time. If too long then try a 10 ohm paralleled next.

>
>
> It may be useful to provide a second output that is scaled such that 0.1
> volts = 10.8:1 and 0.9 volts = 13.07:1 (essentially by subtracting about
> 1.3 volts from the existing output).  This output could be applied to an
> analog mux that selects the stock O2 sensor output under part throttle and
> selects the WB O2 sensor output at WOT.  The output of the mux would
> connect the the ECM O2 sensor input.  This would allow easy WOT A:F ratio
> data capture using the A to D in the ECM in conjunction with an AutoXray or
> Diacom, etc., and would also allow the ECM to continue to operate normally
> at part throttle.

Sounds like a mux should be added to the general output board. I'll keep
this in mind. We are working on a couple of different options at this time. The
re-scaling of the WB output to an ECM O2 input in one of them. I'm not
positive if someone has started working on this one. I'll ask and if not would
you care to? Probably put them all on the same PCB. Good input.


>
>
> I created a Digikey part number BOM from the parts list on the web site.
> Unless it has already been created, I thought that it might be useful to
> have it posted for peer review, corrections, etc.

If you'd like to throw your name at the top and email to me I'll review it. Then

ask Steve if he'd place with the DIY-WB project info page. I like keeping
Steve busy, he does a great job with the web site! (that's a thanks. . .)


>
>
> I'm an EE and moderate the electronics board on thirdgen.org, so I look
> forward to seeing you there, as well!
>
> Tim Burgess

Welcome aboard,

BobR.

>
>



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