o2 sensor

[Barry Tisdale]

Built this thing several months ago using the LM3914 circuit found on the web somewheres.  Only mod I made to it was putting the raw 12-14v power coming in thru a 7809 regulator, thence to the circuitry, w/ a few bypass caps sprinlked here & there - *real* noisy power.  Ref lo is ground, ref hi is whatever voltage you set it to w/ the pot; somewhere's around 1v, to get good full scale reading.  Also used 10meg input resistor.  Only diff between 3 & 4 wire sensors is separate/common grounds for heater & signal.

Got mine mounted on steering column, pretty lights flashing back & forth, and actually *useful* - replaced my O2 sensor recently, flash rate was MUCH faster than w/ the old one, so @ least you can tell when its going.  No real use for tuning, though, too coarse resolution - need a scan tool to do that well.

Barry

At 06:54 PM 6/10/99 +0800, you wrote:
>barry,
>
>thanks for ur comments, i'll let the engine warm up a bit more next time ...
>
>one other quickie, did u get a voltage drop between Ref(hi) and Ref(lo)? i
>didnt, and i'm really puzzled. like i said, commercial meters from cyndyne
>and the like dont have a signal ground input ... so i wonder what do they
>use for Ref(lo)?
>
>sihao