WBO2 testing ... (What I see)

Richard Alan Evans raevans at qwest.net
Wed Dec 19 07:34:28 GMT 2001


Glen:

I've just finished testing my heater section for the first time and
here's what I found. My regulator is mounted to the ~0.040" aluminum
cover of the same Radio Shack box others are using.  I first used a T906
dome light bulb (~1.8 ohms cold). With that I saw a peak current of
~0.59 amps (had a nice soft ramp-up) and about 6 seconds for the LED to
come on.  The regulator didn't heat much if any.

Then I tried an 1156 bulb (~0.5 ohms cold). I got a soft ramp-up to
~1.27 amps and I shut it down after about 1.5 minutes without ever
getting the LED to light.  The regulator did heat up markedly but not to
the point of being untouchable.

I then realized it's not going to work exactly right unless the bulb
resistance matches the O2 heater resistance (~3.3 ohms cold). I gave up
looking for the perfect bulb and since it was exhibiting a soft current
ramp-up, I decided to just try the real thing. (Sometimes I'm
dangerous:) With the real heater, it ramped-up to ~1.27 amps and the LED
came on at 64 seconds. The current settled to ~1.18 after 3 minutes of
on-time in free air. The regulator was merely warm at that point.

Try a bulb closer in cold resistance to the heater resistance the
circuit is designed for and see if it doesn't behave more like it
should.


Glen Beard wrote:
> 
> OK, I've gotten everything soldered up, and I am testing the
> heater circuit using a tail lamp.  The lamp turns on nice
> and bright building its current to 1.003 Amps.  Is the LED
> supposed to turn on after a while?  Is the LT1086 (VR)
> supposed to get sizzling hot even with a 2x3" Al heat sink?
> With the smaller heat sink I had on it, the bulb would light
> up and then start to dim again.  If I blew across it and it
> got brighter.
> 
> --
> Glen Beard  95 T/A conv M6
> 355, Vortech, heads, cam...
> http://home.nycap.rr.com/gbeard1/TransAm.html
> http://home.nycap.rr.com/gbeard1/Impala/Impala.html
> 
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